ML062640270

Tritium Investigation Report, March 2006 - Part 1 of 2

ML062640270
Person / Time
Site:	Braidwood
Issue date:	03/01/2006
From:	Exelon Generation Co
To:	Office of Nuclear Reactor Regulation
References
FOIA/PA-2010-0209, REF 016841 (12)
Download: ML062640270 (338)

Text

TRITIUM INVESTIGATION EXELON GENERATION - BRAIDWOOD STATION BRACEVILLE, ILLINOIS MARCH 2006 REF. NO. 016841 (12)

This report is printed on recycled paper.

TABLE OF CONTENTS Page EXECUTIVE

SUMMARY

.................................................................................................................... i

1.0 INTRODUCTION

...................................................................................................................1 2.0 SITE DESCRIPTION ...............................................................................................................3 2.1 SITE LOCATION AND DEFINITION OF BOUNDARIES ...........................3 2.2 OVERVIEW OF BRAIDWOOD STATION OPERATIONS...........................3 2.3 SURROUNDING LAND USE ...........................................................................4 2.4 OVERVIEW OF GROUNDWATER USE IN THE SITE AREA.....................4

3.0 BACKGROUND

INFORMATION ON THE RELEASES OF TRITIUM .........................6 3.1 BLOWDOWN LINE OPERATION AND RADWASTE TANK DISCHARGES..............................6 3.1.1 BLOWDOWN LINE DESCRIPTION AND PURPOSE ..................................6 3.

1.2 DESCRIPTION

OF THE VACUUM BREAKER VALVES .............................7 3.1.3 PERMITTED DISCHARGES FROM RADWASTE TANKS ..........................7 3.

1.4 DESCRIPTION

OF THE SOURCE OF TRITIUM............................................8 3.2 HISTORY OF VACUUM BREAKER RELEASES............................................8 3.3 PREVIOUS GROUNDWATER STUDIES ......................................................11 3.3.1 POWER PLANT DOCUMENTS - UFSAR REPORT ....................................11 3.3.2 2000 DIESEL FUEL RESPONSE ......................................................................11 3.3.3 2005 INVESTIGATIONS OF TRITIUM IN GROUNDWATER AND SURFACE WATER........................12 3.4 CURRENT REGULATORY STATUS .............................................................13 3.4.1 NPDES AND NRC PERMITS FOR THE BLOWDOWN LINE...................13 3.4.2 DECEMBER 2005 VIOLATION NOTICE ......................................................13 3.4.3 REGULATORY AGENCY COORDINATION ..............................................14 4.0 SITE-SPECIFIC SAMPLING PLAN -

GROUNDWATER INVESTIGATION OF TRITIUM.......................................................16 4.1 PURPOSE AND SEQUENCE OF INVESTIGATIONS................................16 4.2 FIELD STUDIES COMPLETED TO DATE ....................................................17 4.2.1 PERMANENT MONITORING WELL INSTALLATION............................17 4.2.2 PERMANENT MONITORING WELL DEVELOPMENT ...........................18 4.2.3 TEMPORARY MONITORING WELL INSTALLATION ............................18 4.2.4 TEMPORARY MONITORING WELL DEVELOPMENT ............................18 4.2.5 INSTALLATION OF RECOVERY WELLS ....................................................18 4.2.6 RECOVERY WELL DEVELOPMENT ............................................................19 4.2.7 GROUNDWATER AND SURFACE WATER LEVEL MEASUREMENTS ...............................................................19 4.2.8 GROUNDWATER SAMPLING AND ANALYSES......................................19 4.2.8.1 OTHER RADIOISOTOPE ANALYSIS OF GROUNDWATER ...................20 4.2.9 SURFACE WATER SAMPLING .....................................................................21 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

TABLE OF CONTENTS Page 4.2.10 PRIVATE WATER WELL SAMPLING PROGRAMS ..................................21 4.2.11 SINGLE WELL AQUIFER TESTING..............................................................21 4.3 AREA WIDE WATER WELL INVENTORY.................................................22 4.4 REGIONAL HYDROGEOLOGIC DATA COLLECTION ...........................22 4.5 SAMPLING AND ANALYSIS RELATED TO TRITIUM DATING ...........22 5.0 DOCUMENTATION OF FIELD ACTIVITIES -

PRESENTATION OF STUDIES AND ANALYSES COMPLETED TO DATE .............24 5.1 PHYSICAL SITE SETTING ..............................................................................24 5.1.1 REGIONAL TOPOGRAPHY AND SURFACE WATER FEATURES ........24 5.1.2 REGIONAL GEOLOGY ...................................................................................24 5.1.3 REGIONAL HYDROGEOLOGY.....................................................................25 5.1.4 SITE-SPECIFIC TOPOGRAPHY AND SURFACE WATER FEATURES ..26 5.1.5 SITE-SPECIFIC GEOLOGY..............................................................................26 5.1.6 SITE-SPECIFIC HYDROGEOLOGY ...............................................................27

6.0 DESCRIPTION

OF THE CHEMICALS OF CONCERN AND SOURCE AREAS........29 6.1 GENERAL TRITIUM CHARACTERISTICS..................................................29 6.2 CHARACTERISTICS OF WATER IN THE BLOWDOWN LINE - COOLING LAKE WATER QUALITY....................30 6.3 DISTRIBUTION OF TRITIUM IN GROUNDWATER AT THE SITE ........31 6.4 CONCEPTUAL MODEL OF TRITIUM RELEASE AND MIGRATION ...32 7.0 ENDANGERMENT ASSESSMENT ...................................................................................36 7.1 HEALTH EFFECTS OF TRITIUM...................................................................36 7.2 GROUNDWATER STANDARD .....................................................................37 7.3 SITE SPECIFIC BACKGROUND CONCENTRATIONS OF TRITIUM IN GROUNDWATER .......................38 7.4 EXPOSURE ROUTE EVALUATIONS............................................................39 7.4.1 IDENTIFICATION OF POTENTIAL EXPOSURE PATHWAYS AND POTENTIAL RECEPTORS ....................................................................39 7.4.1.1 DIRECT DISCHARGE SCENARIO ................................................................39 7.4.1.2 OVERFLOW SCENARIO .................................................................................40 7.5

SUMMARY

OF EXPOSURE ROUTES............................................................44

8.0 CONCLUSION

S....................................................................................................................46 9.0 PLAN OF ACTION...............................................................................................................48 9.1 FILL DATA GAPS .............................................................................................48 9.2 GROUNDWATER MONITORING ................................................................48 9.3 REMEDIATION.................................................................................................48

10.0 REFERENCES

CITED...........................................................................................................51 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

LIST OF FIGURES (Following Text)

FIGURE 1.1 SITE LOCATION MAP FIGURE 2.1 GENERAL SITE BOUNDARIES AND FEATURES FIGURE 2.2 PRIVATE WATER SUPPLY WELL LOCATIONS FIGURE 3.1 SCHEMATICS OF THE BLOWDOWN LINE AND VACUUM BREAKERS FIGURE 4.1 GROUNDWATER MONITORING LOCATIONS FIGURE 4.2 SURFACE WATER MONITORING LOCATIONS FIGURE 5.1 REGIONAL STRATIGRAPHIC SECTION FIGURE 5.2 REGIONAL DEEP BEDROCK GROUNDWATER LEVEL CONTOURS FIGURE 5.3 SITE SPECIFIC GEOLOGIC CROSS - SECTION FIGURE 5.4 ESTIMATED BOTTOM OF SAND/TOP OF CLAY MAP CONTOURS FIGURE 5.5 VERTICAL GROUNDWATER GRADIENTS ALONG BLOWDOWN LINE FIGURE 5.6 GROUNDWATER LEVEL CONTOURS - JANUARY 2006 - SHALLOW GROUNDWATER ZONE FIGURE 5.7 GROUNDWATER LEVEL CONTOURS - JANUARY 2006 - DEEP GROUNDWATER ZONE FIGURE 6.1 ESTIMATED TRITIUM RESULTS - SHALLOW GROUNDWATER ZONE FIGURE 6.2 ESTIMATED TRITIUM RESULTS - DEEP GROUNDWATER ZONE FIGURE 6.3 MAXIMUM DETECTIONS OF TRITIUM IN THE SHALLOW GROUNDWATER ZONE THROUGH JANUARY 2006 FIGURE 6.4 MAXIMUM DETECTIONS OF TRITIUM IN THE DEEP GROUNDWATER ZONE THROUGH JANUARY 2006 FIGURE 6.5 HYDROGEOLOGIC PROFILE LOCATIONS 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

LIST OF FIGURES (Following Text)

FIGURE 6.6 SITE SPECIFIC HYDROGEOLOGIC PROFILE - JANUARY 2006 (A-A)

FIGURE 6.7 SITE SPECIFIC HYDROGEOLOGIC PROFILE - JANUARY 2006 (B-B)

FIGURE 6.8 MAXIMUM DETECTIONS OF TRITIUM THROUGH JANUARY 2006 IN PRIVATE WELLS FIGURE 7.1 GRAPHICAL PRESENTATION OF BIOSCREEN MODELING RESULTS AND LOCATION OF WATER SUPPLY WELLS 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

LIST OF TABLES (Following Text)

TABLE 4.1

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS TABLE 4.2

SUMMARY

OF GROUNDWATER ELEVATIONS TABLE 4.3

SUMMARY

OF MONITORING WELL PURGING PARAMETERS TABLE 4.4

SUMMARY

OF PRIVATE WATER WELLS DOWNGRADIENT OF THE SITE TABLE 5.1

SUMMARY

OF VERTICAL GRADIENTS AT WELL CLUSTER LOCATIONS TABLE 6.1

SUMMARY

OF GENERAL WATER QUALITY IN BLOWDOWN LINE AND BACKGROUND GROUNDWATER SAMPLES TABLE 6.2

SUMMARY

OF TRITIUM CONCENTRATIONS IN MONITORING WELLS AND SURFACE WATER SAMPLES TABLE 6.3

SUMMARY

OF WEEKLY RESULTS FOR TRITIUM IN KEY MONITORING WELLS AND THE PERIMETER DITCH TABLE 6.4

SUMMARY

OF TRITIUM CONCENTRATIONS IN PRIVATE WELLS TABLE 6.5

SUMMARY

OF INDICATOR PARAMETER SAMPLES IN THE BLOWDOWN LINE, BACKGROUND GROUNDWATER, AND MONITORING WELLS NEAR THE BLOWDOWN LINE 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

LIST OF APPENDICES APPENDIX A CORRESPONDENCE BETWEEN EXELON AND THE IEPA BUREAU OF WATER APPENDIX B FIELD PROCEDURES APPENDIX C MONITORING WELL STRATIGRAPHIC AND INSTRUMENTATION LOGS APPENDIX D RESULTS FROM RADIOISOTOPE ANALYSES (ON CD)

D.1 TRITIUM D.2 OTHER RADIOISOTOPES APPENDIX E ENVIRONMENTAL, INC. QUALITY ASSURANCE PROGRAM APPENDIX F HYDRAULIC CONDUCTIVITY ANALYSES APPENDIX G WATER WELL INVENTORY RECORDS APPENDIX H TRITIUM DATING REPORT BY DR. POREDA APPENDIX I INFORMATION ON COAL MINING ACTIVITIES IN THE SITE AREA APPENDIX J LABORATORY ANALYSES OF GENERAL CHEMISTRY IN THE BLOWDOWN LINE AND GROUNDWATER APPENDIX K CALCULATIONS OF TRITIUM MASS IN GROUNDWATER APPENDIX L BIOSCREEN MODELING RESULTS OF TRITIUM TRANSPORT 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

EXECUTIVE

SUMMARY

Conestoga-Rovers & Associates (CRA) has prepared this Focused Site Characterization Report (FSCR) for Exelon Generation Company, LLC (Exelon) to document findings with regard to the release of tritium into the groundwater at or in the vicinity of the Exelon Braidwood Nuclear Power Station (Braidwood Station) in Braceville, Illinois.

The purpose of this report is to provide a summary of Site characteristics as they relate to the sources, migration pathways, and extent of tritium in groundwater at the Braidwood Station Site. Tritium is the chemical of concern in this focused investigation because it is the only constituent of the releases that exceeds groundwater standards.

This report is the first step taken to pursue cleanup of tritium in the groundwater in a process that is in general compliance with 35 IAC 740 and meets the requirements of 35 IAC 742 Tiered Approach to Corrective Action Objective (TACO). 1 The Site, for the purposes of this FSCR, is defined as the areas of tritium-impacted groundwater resulting from past releases of blowdown line water to groundwater at vacuum breakers (VB) 1, 2, & 3. This FSCR is for an area of investigation bordered by the main generating facility to the west, the Cooling Lake to the south, Comet Drive/Cemetery Road to the east, and Route 53 to the northwest.

Hydrogeology Groundwater use in the Site area is both in the sand aquifer (20 to 30 feet deep) and in the deeper bedrock formations used regionally for municipal and private water supplies (depths of 600 to 1,700 feet). The shallow groundwater flows beneath the Site in a generally south to north manner, flowing from the Cooling Lake toward the ponds located north of the Braidwood Station property. The depth to water in this upper shallow sand aquifer ranges from 5 to 15 feet across the Site. The deeper bedrock water supply aquifers are separated from the shallow system by a number of regional aquitards. These barriers include the Wedron Till Formation (located just beneath the shallow sands) and various shale formations including the Scales Shale, which is over 70 feet thick at the Site and found at depths of 400 feet.

1 This report has many references to Illinois environmental statutes and regulations. By referring to them, we do not intend to imply that they actually apply to the Braidwood tritium releases or have any legal force or effect with respect to these releases. We take no position on this issue. We recognize that the Braidwood plant operates under a license issued by the Nuclear Regulatory Commission and is subject to NRC regulation. We also understand that Exelon Generation Company, LLC takes the position that NRC regulations, rather than Illinois statutes and regulations, apply to the tritium releases.

016841 (12) i CONESTOGA-ROVERS & ASSOCIATES

Source of the Tritium The Site is transversed by the Cooling Lake blowdown line. Within the boundary of the Site, there are three vacuum breaker valves which were installed on the line to prevent damage caused by any vacuum that occurs in the pipe. Braidwood Station uses the blowdown line to return water from the Station Cooling Lake back to the Kankakee River to reduce the dissolved mineral concentration of the water in the lake. The flow in this line historically has ranged from 8,000 to 25,000 gallons per minute. This blowdown line also serves as a permitted discharge point for the Station's sewage treatment plant and the liquid radwaste system under NPDES Permit No. IL0048321.

Under normal operating conditions at Braidwood Station, the principal radionuclide discharged from the plant is tritium. The excess plant water that contains tritium is collected in a liquid radwaste tank and then released periodically to the blowdown line, which discharges to the Kankakee River. The water flowing continuously in the blowdown line contains either:

• only lake water that contains ambient tritium; or

• elevated concentrations of tritium if the radwaste tank is discharging or had just discharged to the line. The source of tritium in the blowdown line is from these intermittent and short duration discharges from the liquid radwaste tank.

For purposes of this report, the specific "Recognized Environment Concerns" at the Site are historic failures of three vacuum breaker valves (VB-1, VB-2, and VB-3), which resulted in the release of tritium to the groundwater beneath the Site. Braidwood Station records, coupled with the existing groundwater data, indicate that the tritium detected in the groundwater in 2005 and 2006 is a direct result of failures at these vacuum breaker valves, which resulted in subsurface and surface releases of blowdown line water at VB-1 (1996, 2000, and 2005), VB-2 (2000), and VB-3 (1998). Pipe integrity testing and groundwater studies along the full length of the blowdown line at the Site do not indicate that the line (pipe) itself is the source of the tritium.

Scope of Work Exelon's initial studies, in the early spring of 2005 found tritium in surface water and groundwater at the Station. These initial studies included sampling private wells to the west of the Site within the Village of Godley and sampling surface water from the perimeter ditch as it flows from east to southwest around the main generating station.

016841 (12) ii CONESTOGA-ROVERS & ASSOCIATES

The discovery of tritium at concentrations that exceeded the ambient (natural for this region) concentrations in the perimeter ditch on the east side of the Braidwood Station property prompted a series of groundwater studies in the summer and fall of 2005.

Exelon implemented an aggressive and comprehensive groundwater investigation program in mid-November 2005. This program also included pipe integrity testing over the full length of the blowdown line. As part of the groundwater studies and the overall groundwater characterization program 2 Exelon has installed over 265 groundwater monitoring points, collected over 420 groundwater samples and surface water samples, and sampled over 47 private wells on multiple occasions. At this specific Site, in the area of vacuum breakers VB-1, VB-2, and VB-3, Exelon has installed 160 permanent and temporary wells and collected over 370 groundwater and surface water samples.

Currently, Exelon is continuing an on-going program of private well sampling and monitoring well sampling at the Site.

The results of the groundwater and surface water studies are presented in this Focused Site Characterization Report. Based on the results of our investigation, CRA concludes:

• Groundwater flow in the shallow sand aquifer, where the tritium is detected, is from south to north;

• Groundwater flow is influenced by the perimeter ditch and by the ponds located to the north and off the Braidwood Station property;

• The underlying deeper groundwater supply aquifers are separated from the tritium in the shallow sand aquifer by the regional Wedron Formation (clayey till) and multiple shale formations, including the 70 foot thick Scales Shale;

• Groundwater flowing from the area on the Braidwood Station property south of Smiley Road discharges into the large pond located to the north;

• The distribution of tritium (and Cooling Lake water indicators) in groundwater is consistent with historical releases from three vacuum breakers on the Site;

• The Braidwood Station records of valve failures and releases of water from the three subject vacuum breakers correlate well with the current distribution of tritium in groundwater;

• At two small areas on the Site tritium concentrations exceed the 35 IAC 620 groundwater standard (20,000 picocuries per liter (pCi/L)). The first area is approximately 4.5 acres near Smiley Road, at the southeast corner of the pond and just west of the blowdown line as it leaves the Station property. The second area is located north of VB-1 and is less than 2.0 acres.

2 For this Site and other areas at the Braidwood Station (e.g., along the blowdown line and the other vacuum breakers).

016841 (12) iii CONESTOGA-ROVERS & ASSOCIATES

• The data collected to date indicates that tritium at concentrations which exceeds the background concentrations (approximately 200 pCi/L) has migrated into and through the pond north of Smiley Road. The distance from vacuum breakers 2 and 3 to the leading edge of this tritium that exceeds the ambient concentration is approximately 2,400 to 2,800 feet;

• Only one private well had groundwater samples collected that were above the ambient levels, but the concentrations at this well were significantly less than the IEPA groundwater standard;

• In the main areas of groundwater impacted by tritium (i.e., those where concentrations are above the groundwater standard) the tritium is more concentrated with depth. The cause of the vertical differences (over a small saturated interval of 20 feet) is believed to be caused by clean water recharge by precipitation. The depth to groundwater is at times less than 5 feet below the ground surface in the areas of tritium impacts and, as such, the upper water table will be flushed with clean precipitation recharge;

• Deeper private water supply wells downgradient of the main tritium impacts were sampled and found to have ambient concentrations of tritium. This supports the role of the regional aquitards (e.g., Wedron clayey till and the Scales Shale) as vertical barriers to deeper migration of tritium. In addition, the lack of any steep downward vertical hydraulic gradients in the shallow sand aquifer would minimize the vertical movement of tritium into the clay;

• Routine monitoring of select groundwater and surface water sample points since November 2005 has indicated stable or decreasing trends in tritium levels in the groundwater;

• The distribution of tritium in groundwater on the upgradient side (to the south) of the pond located north of Smiley Road and the distribution of tritium in groundwater downgradient, or north of the pond, indicates that the pond is acting to reduce the elevated concentrations of tritium discharging into it along Smiley Road.

This mixing and dilution is supported by tritium dating analyses performed by Dr. Robert Poreda of the University of Rochester. His analyses of Site data demonstrated that the pond is mixing on a seasonal basis and therefore is diluting the tritium that discharges from the south. In other words, the pond has played a significant role in preventing higher concentrations of tritium from migrating toward the north; and

• The groundwater flow and tritium migration varies across the Site and is expected to occur at a rate of 80 to 180 feet per year within the upper sand aquifer.

016841 (12) iv CONESTOGA-ROVERS & ASSOCIATES

Exelon is already moving forward with the next phases of work:

• Fill data gaps;

• Implement a groundwater monitoring program; and

• Begin remediation.

The remainder of this Section provides the reader with some of the details of Exelon's on-going efforts.

Remedial Action Plan Exelon has begun to develop interim and long-term remedial actions for the groundwater with tritium in excess of the groundwater standard. An Interim Remedial Action Plan (RAP) has been prepared to support short term actions that will prevent further migration of the tritium and will recover tritium from the main areas impacted.

This RAP has been submitted to the IEPA, the Office of the Attorney General, and the Will County State's Attorney.

Community Relations Plan Finally, as part of the ongoing private well sampling program, and in consultation with the IEPA, Exelon has developed a Community Relations Plan specific to the groundwater tritium issues at this Site. The Community Relations Plan was submitted to the IEPA on March 1, 2006. Exelon will implement this plan as well as continue its on-going coordination with the IEPA, the Nuclear Regulatory Commission (NRC), the Illinois Emergency Management Agency (IEMA), and the Illinois Department of Public Health (IDPH).

016841 (12) v CONESTOGA-ROVERS & ASSOCIATES

1.0 INTRODUCTION

Conestoga-Rovers & Associates (CRA) has prepared this Focused Site Characterization Report (FSCR) for Exelon Generation Company, LLC (Exelon) to document findings with regard to the release of tritium into the groundwater at or in the vicinity of the Exelon Braidwood Nuclear Power Station (Braidwood Station) in Braceville, Illinois (refer to Figure 1.1). Tritium has been detected in the shallow sand aquifer at levels above the Illinois Environmental Protection Agency (IEPA) Groundwater Quality Standards (35 IAC 620 Section 410) in areas east of the main generating facility.

These releases originated at three vacuum breaker (VB) valve locations (VB-1, VB-2, and VB-3) located along the Cooling Lakes blowdown line. Since the spring of 2005, Exelon has undertaken extensive efforts to define and characterize these releases, including extensive sampling of groundwater, surface water, and public wells. As a result of these efforts, Exelon has defined the lateral and vertical extent of the tritium plume and is able to identify those areas both on site and off site where tritium levels exceed either the IEPA groundwater standard of 20,000 picocuries per liter (pCi/L) or the ambient concentration of 200 pCi/L.

Exelon has notified the IEPA, the Nuclear Regulatory Commission (NRC), the Illinois Emergency Management Agency (IEMA), and the Illinois Department of Public Health (IDPH) of the results and since the spring of 2005 has continuously communicated to them information on groundwater conditions. On December 16, 2005, the IEPA Bureau of Water issued a Violation Notice (VN) to Exelon due to the presence of tritium in groundwater. Exelon responded to this notice in a letter to the IEPA, dated February 2, 2006.

A second VN was issued February 27, 2006, and on March 2, 2006 Exelon met with the Attorney General's office, the Will County State's Attorney, the IEPA, and the IEMA to discuss the resolution of this matter. Those discussions are continuing.

The purpose of this report is to summarize for the IEPA and other interested agencies the sources, migration pathways, and extent of tritium in groundwater at the Braidwood Station Site. The only chemical of concern in this focused investigation is tritium.

However, Exelon has sampled and analyzed groundwater for all radionuclides potentially present and for inorganic parameters potentially associated with blowdown water, and tritium is the only constituent measured above its groundwater standard.

This report is considered the first step toward pursuing cleanup of tritium in the groundwater.

016841 (12) 1 CONESTOGA-ROVERS & ASSOCIATES

This FSCR also presents the three dimensional nature of the tritium in groundwater which has migrated in the shallow sand aquifer and, as such, will form the basis of developing a Groundwater Management Zone (GMZ) pursuant to 35 IAC 620 Section 250.

016841 (12) 2 CONESTOGA-ROVERS & ASSOCIATES

2.0 SITE DESCRIPTION 2.1 SITE LOCATION AND DEFINITION OF BOUNDARIES The Site, for the purposes of this FSCR, is defined as the areas of tritium-impacted groundwater resulting from past releases of blowdown line water to groundwater at vacuum breakers 1, 2, & 3. The Site therefore includes areas where tritium exceeds the groundwater standard and where it is detected above the ambient concentration (but below the groundwater standard). Refer to Figure 2.1 for the general Site boundaries.

As seen on Figure 2.1, the Site is located within the Exelon Generation - Braidwood Station property and on adjoining properties to the north. The Site is located near or adjacent to the municipal borders of the Villages of Braidwood, Braceville, and Godley on the southwestern tip of Will County in Illinois (Figure 1.1).

The area of investigation for this Site is bounded to the south by the Cooling Lake, to the northwest by Illinois State Highway 53, to the west by the access road to Braidwood Station, and to the east by Comet Drive/Cemetery Road.

As shown on Figure 2.1, vacuum breaker VB-1 is about 300 feet east of the Station access road and 50 feet south of the switchyard. VB-2 is approximately 3,000 feet to the east of VB-1 along the blowdown line, and VB-3 is approximately 600 feet to the northeast of VB-2 along the blowdown line (Figure 2.1).

2.2 OVERVIEW OF BRAIDWOOD STATION OPERATIONS Braidwood Generating Station is a two-unit nuclear generating facility capable of generating 1,120 net megawatts per unit. Units 1 and 2 are pressurized water reactors (PWRs) designed by Westinghouse and began commercial operation in July and October 1988, respectively. A PWR plant consists of three separate loops of fluids. Each loop is designed to avoid mixing the fluids of one loop with the fluids of another. The loops are called the primary loop, the secondary loop, and the tertiary loop.

The main purpose of the primary loop is to transfer the energy generated from fission in the fuel to the secondary loop steam generators. It is a closed loop system. Nuclear fission creates heat in the fuel. This heat is removed by the flow of reactor coolant water through the reactor vessel and into the steam generators. The heat is transferred to the secondary side where steam is generated. The water is then pumped back to the reactor vessel to cool the fuel again.

016841 (12) 3 CONESTOGA-ROVERS & ASSOCIATES

The main purpose of the secondary loop is to use the steam generated in the steam generators to turn the turbine generator, which makes electricity. It is also a closed system.

The main purpose of the tertiary loop is to use cooler lake water to condense the steam in the condenser and transfer the heat to the atmosphere. This loop needs makeup water to operate properly. Makeup water comes from the Kankakee River.

As the steam is condensed in the condenser, the circulating water becomes hotter. The circulating water is discharged to the Cooling Lake where it loses some of its heat through evaporation. The now cooler water is then pumped backed to the condenser to start the loop over again.

2.3 SURROUNDING LAND USE Land surrounding the Site falls mainly into the agricultural, residential, and recreational use categories. Residential lots surround the Site to the north and to the east along Smiley Road and Center Street. Further to the north, there are several ponds or small lakes. The center of the Village of Braidwood is approximately 8,000 feet from the Site measured from Smiley Road. To the northwest of the Site, there are two main highways (Illinois State Highway 53 and Illinois Route 129) running parallel to each other with a railroad (Southern Pacific Railroad) between them. Within the southern portion of the Site is the Cooling Lake that is used as a recreational area in the summer for boating and fishing by the Illinois Department of Natural Resources (IDNR).

2.4 OVERVIEW OF GROUNDWATER USE IN THE SITE AREA The groundwater beneath Braidwood Station is not used as a potable resource for its operations. The Braidwood Station obtains all of its water requirements from the Kankakee River. There are a number of domestic wells near the Site (see Figure 2.2 for private well locations) that obtain their water from the underlying shallow sand aquifer, which comprises Quaternary age eolian and lacustrine sands to a depth of approximately 30 feet below ground surface. These sands overlie glacial drift (till) deposits that overlie bedrock. The glacial till ranges from clay to gravel but is predominantly clayey till. The groundwater within this shallow sand aquifer is under water table conditions with the depth to water ranging from 5 to 15 feet below the land surface. The shallow aquifer is recharged by precipitation and the groundwater within the shallow aquifer discharges to nearby surface streams and strip mines. The well 016841 (12) 4 CONESTOGA-ROVERS & ASSOCIATES

yields from the shallow aquifer, which range from 2 to 5 gallons per minute (gpm), are only suitable for domestic or farming purposes.

The Quaternary age deposits (shallow sand aquifer) are underlain by Pennsylvanian bedrock composed of siltstone, shale, sandstone, clay, limestone, and coal. The Pennsylvanian strata may locally yield up to 20 gpm from the interbedded sandstones.

The Cambrian-Ordovician aquifer is composed of a number of strata as outlined in Section 5.0. Water supply wells completed in this aquifer are at depths of over 600 feet.

The next major aquifer is the Mt. Simon, which is found at depths of over 1,400 feet.

Most of the groundwater supply wells within the surrounding area of the Braidwood Station are finished within these deeper aquifers (depths of 100 feet, and of 600 to 1,600 feet). There are a smaller number of water supply wells that are completed in the shallow sand aquifer. Further discussion on the Site geology, groundwater use, and groundwater supply wells is presented in Section 5.0. The Village of Braidwood, which is approximately 11/2 miles north of the Site, provides municipal water via at least one deep bedrock water supply well that has a depth of over 1,600 feet.

016841 (12) 5 CONESTOGA-ROVERS & ASSOCIATES

3.0 BACKGROUND

INFORMATION ON THE RELEASES OF TRITIUM This section of the report provides information documenting the source of the tritium in the blowdown line, the operation of the blowdown line and the vacuum breaker valves, and the failures of these valves as they relate to groundwater impacts. The studies clearly show that the three vacuum breakers located just east of the main generation facility (VB-1, VB-2, and VB-3) are the source of the tritium. As such, these three vacuum breakers are considered to be the "Recognized Environmental Conditions", or "RECs", for the purpose of this Focused Site Characterization Report. The historical releases from each of these vacuum breakers are documented and discussed further in Sections 3.2 and 6.4. In addition, integrity testing of the blowdown line and groundwater studies near the blowdown line (refer to Section 6.4.1) have demonstrated that the pipe itself is not a REC and that the historical releases of water at the vacuum breakers fully explain the current distribution of tritium in the groundwater. The following discussions provide operational and historical information on the blowdown line and the vacuum breaker valves.

3.1 BLOWDOWN LINE OPERATION AND RADWASTE TANK DISCHARGES Braidwood Station employs a blowdown line to return water from the Cooling Lake back to the Kankakee River for the purposes of reducing the dissolved mineral concentration of the lake water (refer to Figure 1.1). This blowdown line also serves as a permitted discharge point for the Station's sewage treatment plant and the liquid radwaste system. Further details on the operation and normal discharges through the blowdown line are provided in the following sections.

3.1.1 BLOWDOWN LINE DESCRIPTION AND PURPOSE The blowdown line is constructed of a steel shell that is lined with concrete. The outside is covered with prestressed steel wire and concrete. The bell and spigot joints have a rubber gasket that seals the steel shells, and these joints are grouted inside and outside.

The pipe is designed to withstand an internal pressure of 110 pounds per square inch (psig) but the system normally operates below 20 psig. In addition to the vacuum breaker valve, there is an air-release valve that allows small amounts of air to be released from the line so that the larger vacuum breaker does not cycle to relieve this air (Figure 3.1).

016841 (12) 6 CONESTOGA-ROVERS & ASSOCIATES

Braidwood Station uses a Cooling Lake to provide a heat sink for its main condensers.

Since the lake is warm and has a large surface area, it loses much of its water to evaporation. Evaporation of the water concentrates dissolved and suspended minerals in the lake. High concentrations of dissolved minerals, especially calcium carbonate, can result in calcium deposits on the Plant's heat exchangers, reducing their performance.

To reduce the concentration of dissolved minerals in the lake, Exelon discharges roughly 25,000 gpm of water to the Kankakee River through the blowdown line. Historically, flow rates were as low as 8,000 to 25,000 gpm. Exelon increased blowdown flow over the years to improve Cooling Lake chemistry. Approximately 48,000 gpm of water is pumped from the river to the lake, through the makeup line to compensate for losses due to evaporation and blowdown. The makeup line was installed parallel to the blowdown line.

Figure 1.1 presents a plan view of the blowdown line as it traverses from west to east across the Site, just north of the Cooling Lake. Figure 2.1 shows the location of the blowdown line and the makeup line in the Site area. Figure 3.1 presents a portion of the profile of the construction of the blowdown line (and makeup water line) and their placement in the subsurface.

3.

1.2 DESCRIPTION

OF THE VACUUM BREAKER VALVES The blowdown line is partly constructed of concrete, and it is not capable of withstanding any vacuum. Therefore, the pipe is fitted with 11 float-operated vacuum breaker valves. The makeup and blowdown lines are both fitted with vacuum breaker valves that allow air to escape as the lines are filled and allow air to enter the pipe when pressure and water levels in the pipe are low. The valves are 6-, 8-, or 10-inch nominal size and employ a stainless steel float to open and close the openings. Figure 3.1 presents a schematic of a typical vacuum breaker valve.

3.1.3 PERMITTED DISCHARGES FROM RADWASTE TANKS Excess plant water that contains tritium is periodically released via the blowdown line to the Kankakee River. This discharge meets federal requirements. IEPA NPDES Permit No. IL0048321 allows for liquid radwaste discharges to the blowdown line. In addition, as required in the NRC's regulations (10 CFR 20, 10 CFR 50, and 40 CFR 190), the Braidwood Station has developed an Offsite Dose Calculation Model (ODCM), which it uses to monitor and limit the radioactive effluents from the plant.

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3.

1.4 DESCRIPTION

OF THE SOURCE OF TRITIUM Under normal operating conditions at Braidwood Station, the principal radionuclide discharged from the plant is tritium. Tritium is formed when a neutron is captured by the boron and/or lithium in the coolant. Excess plant water that contains tritium is periodically released to the Kankakee River.

3.2 HISTORY OF VACUUM BREAKER RELEASES This section presents a description of the permitted liquid radwaste discharges to the blowdown line. This description is followed by a summary of the documented significant releases at each of the subject vacuum breakers (VB-1, VB-2, and VB-3). The scope of this report is limited to the tritium releases to the groundwater from vacuum breakers 1, 2, and 3.

The Liquid Radwaste Discharge Process Typically the station releases tritiated water every 3 days from the 25,000 gallon liquid radwaste tank. However, during outages there can be a release from the tank daily.

Prior to August of 2003, the typical flow rates in the blowdown line were 10,000 to 12,000 gpm. However, after 2003, the average flow rates were 20,000 to 25,000 gpm. The tritium concentration of water flowing within the blowdown line changes depending on whether there is a radwaste release tank being discharged at the time of the measurement. When no tritiated water is being discharged from the storage tank, the tritium concentration is that of the Cooling Lake, which is essentially ambient or background.

During a release, the concentration of tritium in the line will be significantly higher. The average tritium concentration during releases exceeds 1,000,000 pCi/L. 1 However, this is an average of water flowing in the blowdown line for only the period that the radwaste tank is actually discharging to the blowdown line, which typically ranges between 60 and 300 minutes. If a composite water sample were drawn by extracting a small continuous sample from the line (during a longer period when multiple radwaste tank releases occurred followed by periods of blowdown from the Cooling Lake), then 1 This average concentration is based upon a calculation performed by Exelon using records of releases from Braidwood Station, specifically, the blowdown line tritium concentration was derived using actual isotope and other release data collected from each release tank and the measured (or estimated) blowdown line flow rate. These records are available at the Braidwood Station.

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the composite concentration would be much less than 1,000,000 pCi/L and on the order of 40,000 to 100,000 pCi/L depending on the blowdown line flow. 2 Since the tritium concentration of the blowdown line varies, it is important to recognize that a continuous leak would have an average concentration equal to the composite concentration of the blowdown line during the time the leak was active. Conversely, a large leak from a vacuum breaker could happen during a release from the radwaste tank and not become well mixed before entering the ground. This could account for concentrations of tritium that exceeded the composite values. The remainder of this section provides a discussion on the history of leaks from VB-1, VB-2, and VB-3.

Vacuum Breaker 1:

On December 1, 1996, Exelon discovered a leak at VB-1. The leak was in the 1-inch pipe to the air release valve. The valve had last been inspected in June of 1995 at which time no leaks had been noticed. The line eventually broke and was repaired in June of 1997.

The volume of water that leaked was not recorded. However, Exelon estimated that the total leakage from VB-1 was between 120,000 to 380,000 gallons. Since the leak occurred over many weeks, this leak would have included liquid radwaste release water (containing tritium) in addition to the water from the Cooling Lake.

On November 20, 2000, Exelon discovered a leak when personnel noticed that water was flowing upward from the vacuum breaker pit through the manway cover and flooding the surrounding area. The responsible valve was repaired the next day. Exelon estimates that this leak was less than 4 million gallons. Sampling data indicate that this leak contained no tritium, suggesting that the leak likely occurred between releases from the radwaste tank.

On May 19, 2005, a leak at a rate of approximately 20 drops per minute was discovered at the pilot (air release) valve seat. The valve had been previously inspected in November 2004. The total leakage was to be estimated between 60 and 140 gallons. The repair was completed in October 2005. Again, the concentration of the tritium in the droplets is estimated to be a composite of flow in the line during 2005. Composite water (water in the pit) from the pilot valve leak identified in May 2005 was sampled and analyzed. The water sample contained 51,295 pCi/L of tritium. This was not, however, a sample of the groundwater, because the water was collected off of components within 2 This is based upon calculations made by Exelon using records from the Braidwood Station. Composite values were determined using the existing records and applying the rates to the duration of each leak.

Again, these records are available at the Braidwood Station.

016841 (12) 9 CONESTOGA-ROVERS & ASSOCIATES

the valve pit and probably represented a composite of tritium levels within the blowdown line.

Vacuum Breaker 2:

In November 2000, a resident reported flooding of the ditch adjacent to Braidwood Station to the IEPA, which informed Braidwood Station. Exelon detected a leak from VB-2 as a result of vacuum breaker valve float failure that was repaired in December 2000. The Station pumped all standing water back into the blowdown line. This leak was caused by a water hammer, which broke the float in the valve, exposing an 8-inch opening. Exelon's analysis of their records 30 days prior to isolating this leak reveals:

• The average tritium concentration during releases was 1,305,000 pCi/L.

• The maximum tritium concentration in the pipeline during this period was 3,103,000 pCi/L. 3

• If a composite sample were drawn by extracting a small continuous sample from the line for the same 30-day period, the composite concentration would be roughly 91,400 pCi/L.

Vacuum Breaker 3:

In December 1998, there was a leak from VB-3 that was caused by a failed vacuum breaker float. This valve was found leaking due to flooding of the Smiley Road ditch on December 3, 1998. The valve was repaired on December 4, 1998. This valve was last inspected in December 1997, and no leakage was noted. The volume of the leak was not recorded, but was later estimated to be 3 million gallons over a 30-day period.

Exelon's records indicate that the historic releases and their estimated concentrations were:

• In 1998, the average blowdown line flow rate was 10,000 to 12,000 gallons per minute.

• In the 30 days prior to discovering the leak at VB-3, there were 24 releases from the radwaste tanks to the blowdown line.

• For the 30-day period prior to discovering the leak at VB-3, the average tritium concentration in the blow pipe was 624,000 pCi/L.3 3 It is important to note that by the time these releases discharge into the Kankakee River that the tritium levels are significantly below the Federal limits as noted in the ODCM.

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• The highest tritium concentration in the pipeline during this period was 1,852,000 pCi/L.3

• If a composite sample were drawn by extracting a small continuous sample from the line for the same 30-day period, the composite concentration would be 112,000 pCi/L.3 3.3 PREVIOUS GROUNDWATER STUDIES There are numerous studies of the local geology and groundwater. These studies provide a comprehensive understanding of the hydrogeologic conditions on the east side of the Braidwood Station. The remainder of this section presents a brief description of these previous studies. Additional findings are discussed in Section 5.0.

3.3.1 POWER PLANT DOCUMENTS - UFSAR REPORT During the construction of the Braidwood Station, a series of comprehensive investigations of regional and local geology and of surface water and groundwater conditions were conducted. These studies were performed for a number of purposes including geotechnical evaluations of the underlying geologic deposits, engineering designs for the slurry wall around the Cooling Lake, present and future sources of groundwater, present and future groundwater use, and other engineering and environmental purposes.

These studies are documented in the Updated Final Safety Analysis Report (UFSAR),

which was prepared by Sargent and Lundy (December 1988). Much of the current understanding of the geology and the groundwater conditions is based upon the information in the UFSAR.

3.3.2 2000 DIESEL FUEL RESPONSE On August 4, 2000, Exelon entered into the Illinois SRP in response to releases of diesel fuel from the west side of the main generating facility at the Braidwood Station on June 24, 2000. Beginning in 2001, Exelon initiated studies to address the conditions of soils, surface water, and groundwater on the northwest corner of the station. These studies determined the nature of flow in the shallow sand aquifer and its hydraulic relationship with the perimeter ditch that flows around the station from east to west.

016841 (12) 11 CONESTOGA-ROVERS & ASSOCIATES

Exelon submitted a number of documents to the IEPA under the SRP for this diesel fuel release. On January 27, 2005, the IEPA issued a No Further Remediation (NFR) letter to Exelon for the diesel fuel release.

3.3.3 2005 INVESTIGATIONS OF TRITIUM IN GROUNDWATER AND SURFACE WATER In early spring of 2005, Exelon initiated investigations into the potential occurrence of tritium in water within the perimeter ditch (the drainage ditch that flows around the station). Initially, the studies were focused on the area west of the generating station (near the Village of Godley). Later, however, surface water samples collected upstream in the perimeter ditch and to the east of the Braidwood Station also found tritium above ambient concentrations. When elevated tritium was detected in the surface water at locations to the east, Exelon initiated a groundwater investigation based upon its experiences during the groundwater studies for the diesel fuel spill in 2000 4 .

In the spring of 2005, Exelon initiated a groundwater monitoring program to determine the source and extent of tritium in the perimeter ditch and in the shallow groundwater on the east side of the Station. In the fall of 2005, groundwater samples collected at the northern property line (near Smiley Road) contained elevated levels of tritium that exceeded background levels (200 pCi/L), but were well below the Illinois groundwater standard of 20,000 pCi/L. After obtaining these results, Exelon took additional steps to investigate the source of the tritium and its extent in the groundwater. It installed monitoring wells at its northern property boundary and other wells downgradient of the most likely sources of the tritium (vacuum breakers).

In November 2005, Exelon undertook other studies to determine:

• the sources of the tritium in the groundwater;

• the lateral and vertical extent of the tritium in groundwater on and off the property; and

• when the releases had occurred and whether releases were still continuing.

4 In October 2000, in response to a release of water from VB-2, Exelon installed four shallow monitoring wells (MW-101 to MW-104) in order to determine the direction and rate of groundwater flow near of VB-2.

016841 (12) 12 CONESTOGA-ROVERS & ASSOCIATES

These studies continued through February 2006 and form the basis of this FSCR and of the current understanding of the nature and extent of tritium in the groundwater at the Site.

At the time of this report approximately 300 groundwater samples and surface water samples were collected from permanent monitoring wells, temporary wells, ponds, ditches, and private residence wells. In the area downgradient from VB-1, VB-2, and VB-3, Exelon has sampled 15 private residence wells. Many of the domestic wells are being sampled routinely.

3.4 CURRENT REGULATORY STATUS Braidwood Station is subject to a number of regulatory permits and notices. The remainder of this section discusses the primary permits.

3.4.1 NPDES AND NRC PERMITS FOR THE BLOWDOWN LINE The blowdown line and the Cooling Lake water makeup line transverse the Site area in the south. The blowdown line is subject to regulation under the IEPA NPDES Permit (IL0048321) and the Braidwood Station ODCM. The NPDES permit provides limits on parameters such as pH, Total Suspended Solids, BOD5, Oil and Grease, Total Residual Chlorine, Total Residual Oxidant, and temperature. The permit also requires monitoring of parameters such as blowdown discharge flow. The ODCM is the document required in the NRC's regulations (10 CFR 20, 10 CFR 50, and 40 CFR 190) to monitor and limit the radioactive effluents from the plant. The ODCM places limits on concentrations of radioactive effluents released and requires monitoring of the concentrations of these effluents.

3.4.2 DECEMBER 2005 VIOLATION NOTICE In a letter dated December 16, 2005, Exelon received a Violation Notice from the IEPA Bureau of Water. This letter was a response to the tritium that exceeded the 35 IAC 620 groundwater standard (20,000 pCi/L).

Exelon responded to the December 16th Violation Notice in a letter, dated February 2, 2006. In their February 2nd letter, Exelon committed to entering the IEPA SRP and to 016841 (12) 13 CONESTOGA-ROVERS & ASSOCIATES

preparing this Focused Site Characterization Report. The February 2nd letter also contains a schedule to develop deliverables and plans required under the SRP with the goal of remediating the Site and obtaining an NFR letter. The IEPA's December 16, 2005 Violation Notice letter and Exelon's February 2, 2006 response letter are in Appendix A.

On February 17, 2006, Exelon met with the IEPA to discuss the VN and Exelon's plans to remediate the tritium. On March 2, 2006, Exelon met with the IEPA, the IEMA, the Office of the Attorney General, and the Will County State's Attorney to discuss this matter. As part of this process, Exelon has prepared the FSCR for submittal to the IEPA, the Office of the Attorney General, and the Will County State's Attorney.

3.4.3 REGULATORY AGENCY COORDINATION Since the Spring of 2005, when the surface water in the perimeter ditch was found to contain tritium, Exelon has regularly communicated with these agencies:

• IEMA;

• IDPH;

• NRC;

• IEPA Bureau of Water; and

• Office of the Illinois Attorney General.

In addition, Exelon has been providing these agencies regular updates of investigative plans, the status of sampling programs, and preliminary analytical data. Both the preliminary and final analytical results of all groundwater analyses have been provided to the IEMA and to the NRC as soon as they are available. In addition, since November 2005, Exelon has attended the following meetings :

• December 20, 2005 with the IEPA, IEMA, NRC, and IDPH in Springfield to discuss the current understanding of the source of the tritium, the known extent of the tritium, and the future sampling program;

• January 23, 2006 with the IEPA, IEMA, NRC, and IDPH in Springfield to discuss recent findings and the proposed response and actions to be taken with respect to the Notice of Violation;

• February 17, 2006 meeting with the IEPA to discuss the compliance commitment agreement; and

• March 2, 2006 meeting at the Attorney General's office.

016841 (12) 14 CONESTOGA-ROVERS & ASSOCIATES

Exelon has also had a number of meetings with local property owners and area residents. Exelon has developed a Community Relations Plan, and this has been provided to the IEPA under separate cover (March 1, 2006). As part of this plan, Exelon held an open house information forum on February 28, 2006 at the Exelon Training Center along Essex Road. This forum was open to all interested members of the public.

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4.0 SITE-SPECIFIC SAMPLING PLAN -

GROUNDWATER INVESTIGATION OF TRITIUM 4.1 PURPOSE AND SEQUENCE OF INVESTIGATIONS The investigations of tritium in groundwater at the Braidwood Station began in early Spring of 2005. 5 The initial investigation included drilling and sampling permanent wells around each of the three subject vacuum breakers (VB-1, VB-2, and VB-3) to determine groundwater flow directions and the concentration of tritium in the groundwater. Based upon the results from the monitoring wells installed in July 2005 (MW-105 to MW-109), additional monitoring wells were installed in September 2005 downgradient (to the north) of the vacuum breakers and at the Braidwood Station property line (MW-110 to MW-113) to determine if tritium above the ambient concentration was migrating off Site.

The analytical results from monitoring wells at the property line, specifically the tritium concentrations in MW-113 (the initial sample collected October 19, 2005 had a tritium result of 4,480 pCi/L), lead to the development of an aggressive investigation program and an Exelon Task Force to address the presence of tritium on and off the Braidwood Station property. This program consisted of the installation and sampling of temporary wells that were installed at shallow and deeper depths within the upper sand aquifer between November 2005 and February 2006. The goals of the aggressive investigative program were to determine :

• the source of the tritium;

• the lateral and vertical extent of the tritium in groundwater on and off site; and

• when the releases had occurred and whether releases were still continuing.

This section of the report provides an overview of the field studies completed from 2005 to the time this report. This section includes the number, location, type, and methods of sample collection.

Figure 4.1 presents the location of all groundwater monitoring points (temporary wells and permanent wells). Figure 4.2 presents the locations of surface water bodies sampled and monitored, including the perimeter ditch and off-property ponds. Figure 2.2 presents the locations and identifiers of private wells sampled as part of the investigations in the area north of Smiley Road.

5 Groundwater flow was determined in an area near VB-2 during an investigation of the leak from this vacuum breaker in November 2000.

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4.2 FIELD STUDIES COMPLETED TO DATE CRA retained Terra-Trace Environmental Services (Terra-Trace) of Lake Bluff, Illinois to install the temporary wells, Altech Services, LLC (Altech) of Livonia, Michigan to install the permanent wells, and Boart Longyear Company (Boart) of Schofield, Wisconsin to install the recovery wells. Drilling investigations began in July 2005 and were completed in February 2006. A total of 156 wells consisting of 143 temporary wells, 9 permanent wells, and four recovery wells, were installed at the Site during this time period (four permanent wells had been installed previously in 2000). Figure 4.1 presents groundwater monitoring locations. Figure 4.2 presents surface water monitoring locations. Table 4.1 presents monitoring wells specifications.

Three staff gauges (SG-A, SG-B, and SG-C) were installed in three ponds located north of Smiley Road. Surface water samples were collected from these ponds and the perimeter ditch.

Single well aquifer testing was conducted at four permanent wells on October 20, 2005 and at two temporary wells on February 2, 2006.

The sections below outline a brief discussion of the field activities performed and work completed to date. Appendix B provides a complete discussion of the methods used to perform the field activities.

4.2.1 PERMANENT MONITORING WELL INSTALLATION CRA oversaw the installation of four permanent monitoring wells (MW-101 through MW-104) at the Site in November 2000 to determine the direction of groundwater flow.

Five permanent monitoring wells (MW-105 through MW-109) were installed on July 26 and 27, 2005 for groundwater flow and tritium analyses. Four permanent monitoring wells (MW-110 through MW-113) were later installed on September 18, 2005 as part of the tritium investigation. All wells except for MW-110 were advanced to 16 feet below ground surface (bgs). MW-110 was advanced to 20 feet bgs. The monitoring wells were installed so that the well screen straddled the water table at depths of 15 to 20 feet bgs.

Subsequent sampling of deeper wells indicated a need to install permanent and temporary monitoring wells deeper and to the bottom of the sand zone (25 to 30 feet 016841 (12) 17 CONESTOGA-ROVERS & ASSOCIATES

bgs). Monitoring wells MW-105D, MW-106D, MW-111D, MW-112D, and MW-113D were installed during December 2005 and January 2006 to depths of 24 to 27 feet bgs.

Well completion forms and stratigraphic logs are in Appendix C.

4.2.2 PERMANENT MONITORING WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the permanent wells were developed.

4.2.3 TEMPORARY MONITORING WELL INSTALLATION Beginning in November 2005 and extending through February 2006, 216 shallow and deep temporary wells were installed using direct push (Geoprobe) methods. The use of the Geoprobe drilling technique and the installation of temporary 1-inch diameter monitoring wells allowed easy and fast collection of groundwater levels and groundwater samples for tritium analyses. Shallow wells range in depth from 11 to 21 feet bgs. Deep wells range in depth from 21 to 41 feet bgs. Deep wells were installed to the top of the underlying clay layer, the location of which was determined at each location in one of two ways. The top of the clay layer was identified by using a Geoprobe macrocore and visually looking at the soil sample retrieved in the macrocore or by a noticeable change in resistance encountered by the Geoprobe as noted by the Geoprobe operator.

Well completion forms and stratigraphic logs are in Appendix C.

4.2.4 TEMPORARY MONITORING WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the temporary wells were developed.

4.2.5 INSTALLATION OF RECOVERY WELLS In anticipation of possible hydraulic control or tritium recovery actions, four recovery wells (RW-1 through RW-4) were installed on December 1 and 2, 2005 as a contingency.

The recovery wells were advanced to reach the top of the underlying clay layer, between 24 to 28 feet bgs.

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Well completion forms and stratigraphic logs are in Appendix C.

4.2.6 RECOVERY WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the recovery wells were developed.

4.2.7 GROUNDWATER AND SURFACE WATER LEVEL MEASUREMENTS The depth to water in each well was measured to the nearest 0.01 foot using an electronic water level meter. Measurements were recorded after each well installation and at each sampling event. Surface water level measurements were recorded by reading the staff gauges (SG-A, SG-B, and SG-C). Currently, water levels at the staff gauges are read on a routine basis.

The water level data are presented in Table 4.2.

4.2.8 GROUNDWATER SAMPLING AND ANALYSES A total of 13 permanent, 143 temporary, and four recovery wells were sampled during this investigation. All 160 permanent, temporary, and recovery wells were sampled and analyzed for tritium in the Site area. In addition, two samples (RW-1 and RW-2) were analyzed for total metals and general chemistry. Twenty-four samples (BL-01 through BL-08, BL-10 through BL-16, BL-10D through BL-17D) were analyzed for sodium and chloride. The sodium and chloride were analyzed at these sampling points located along the blowdown line based on general chemistry sample analyses for the blowdown line. Two samples of water in the blowdown line itself and two background wells were sampled and analyzed for a full suite of general chemistry parameters. These samples were collected to look for indication of leaks within the blowdown line. Refer to Section 6.2 for further discussion. In addition, samples were also analyzed for other radioisotopes present in the liquid radwaste discharges (refer to Section 4.2.8.1).

Groundwater samples collected for tritium analyses were delivered to an Exelon representative, who submitted them to Environmental, Inc. of Northbrook, Illinois, to the IEMA, and to the NRC for analyses. Groundwater samples collected for total metals, general chemistry, sodium and chloride analyses were hand delivered to First 016841 (12) 19 CONESTOGA-ROVERS & ASSOCIATES

Environmental Laboratories, Inc. (First Environmental) of Naperville, Illinois. Results of tritium analyses and of other radioisotopes analyses are in Appendix D. This appendix includes copies of laboratory reports from Environmental, Inc., and these are presented on a CD.

To better evaluate the potential for past leaks or on-going leaks from the vacuum breakers and from the blowdown line, the general chemistry of the water flowing in the blowdown line was analyzed. Samples from the blowdown line and from representative groundwater monitoring locations were analyzed for a set of typical groundwater quality parameters (e.g., anions, cations, metals, etc.) by First Environmental. These samples were used to develop a list of indicator parameters (excluding tritium) for water flowing in the line. These analytical results are discussed in Section 6.2.

The quality assurance procedures and protocols used by Environmental, Inc. for the tritium analyses and for the other radioisotopes are in Appendix E. Environmental, Inc.

is the only independent laboratory certified by the State of Illinois to conduct radiological testing of groundwater.

Monitoring wells were purged prior to sample collection (see Table 4.3 for purging parameters). Groundwater samples were collected in accordance with the CRA Slow Purging/Minimal Disturbance Protocols specified in Appendix B. The CRA procedures were further expanded to address the requirements of Exelon, Environmental, Inc., and Site conditions. The CRA procedures were supplemented with Exelons protocols as specified in Appendix B.

4.2.8.1 OTHER RADIOISOTOPE ANALYSIS OF GROUNDWATER In addition to the sampling and analysis of the groundwater for tritium, the primary radioisotope discharged to the blowdown line from the liquid radwaste tank, Exelon also analyzed for other radioisotopes. The initial set of groundwater samples collected from the monitoring points were also analyzed for a specific set of radioisotopes that were present in the liquid radwaste tank, but at much lower concentrations than tritium.

This included sample analysis by Environmental, Inc. for parameters such as Cobalt-58, Cesium-134, and others. Appendix D provides the results from these specific radioisotope analyses. In the Site area, over 150 groundwater samples were submitted to Environmental, Inc. for these specific radioisotope analyses.

016841 (12) 20 CONESTOGA-ROVERS & ASSOCIATES

4.2.9 SURFACE WATER SAMPLING Surface water samples were collected at several locations beginning in November 2005.

On November 30, 2005, two surface samples were collected from the pond located at Center Street and Smiley Road (surface water locations SW-1 and SW-2). On December 2, 2005, two surface samples were collected from Fatlan Pond, located west of Center Street (locations SW-3 and SW-4). Surface water location SW-2 was sampled again on January 11, 18, and 25, 2006, and February 1, 2006. One surface water sample was collected from Zimmer Pond, located west of Comet Drive (location SW-5), on January 30, 2006. Surface sample PW-6P was collected from Scamen Pond on February 9, 2006. A surface sample was taken from Fatlan Pond on February 9, 2006.

Currently, surface location SW-2 is being sampled on a weekly basis. Figure 4.2 provides surface water sampling locations.

4.2.10 PRIVATE WATER WELL SAMPLING PROGRAMS Exelon initiated sampling of nearby private wells in November 2005. Since the initial samples collected on November 30, 2005, a routine program has been developed and implemented by CRA. This routine private well sampling program applies to 15 locations (residences) found north of Smiley Road and downgradient of the impacted groundwater areas (see Figure 2.2).

4.2.11 SINGLE WELL AQUIFER TESTING Single well hydraulic response tests were performed on site on October 20, 2005 on four permanent wells (MW-105, MW-107, MW-109, and MW-112). Single well hydraulic response tests were performed off site on February 2, 2006 on two temporary wells (P-2 and G-2). The response tests were performed in order to determine the hydraulic conductivity of the aquifer in these areas. The tests were performed using rising head methods, wherein the water level in a monitoring well is depressed and water level recovery is monitored over time. A pressure transducer and data logger monitored water levels. Data obtained from the single well response tests was evaluated using the methods developed by Bouwer & Rice (1976).

The geometric mean for the test results from October 20, 2005 indicate a site-specific hydraulic conductivity of 2.5 x 10-2 cm/sec. The geometric mean for the test results from February 2, 2006 indicate a site-specific hydraulic conductivity of 3.7 x 10-2 cm/sec.

Hydraulic conductivity analyses are in Appendix F.

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4.3 AREA WIDE WATER WELL INVENTORY CRA collected a water well inventory from the Illinois State Water Surveys Private Well Database and Public, Industrial, Commercial Survey (PICS) Database in November 2005, December 2005, and January 2006. The well inventory was collected for the area one mile north and one mile south of Smiley Road and one mile north and one mile south of the blowdown line for the area east of vacuum breaker VB-4 to the Kankakee River. The Private Well and PICS Database queries well records by county, township, range, and section.

The search included records from Will County, Township 32N, Range 9E and Sections 13 to 17, 20 to 24, and Range 10E Sections 18 and 19. The inventory produced 429 records total; 46 of these records (see Table 4.4) are downgradient (north) of the Site.

The water well inventory provides information about the water well owner, driller, drill date, depth, and if available address, well type, aquifer type, static water level, and pump level. A collection of findings from the well inventory is in Appendix G.

4.4 REGIONAL HYDROGEOLOGIC DATA COLLECTION As part of the characterization of Site conditions, CRA requested regional hydrogeologic data from the Illinois State Geological Survey (ISGS) and the Illinois State Water Survey (ISWS). Some of this information has not yet been received but will be incorporated into future evaluations.

4.5 SAMPLING AND ANALYSIS RELATED TO TRITIUM DATING Exelon retained Dr. Robert Poreda of the University of Rochester to evaluate the age of the tritium found in the groundwater at the Site. The main purpose of the tritium dating analysis was to evaluate whether there was any indication of an active leak from the vacuum breakers or from the blowdown line. In addition, the results of the tritium dating analysis was used to confirm the conceptual site model presented in Section 6.0.

Dr. Poreda accompanied CRA to the Site on December 22, 2005 and collected groundwater samples for his analyses from 14 groundwater monitoring locations across the Site. These samples were collected from wells completed in the shallow and in the deep groundwater zone. In addition, the samples were collected across the tritium 016841 (12) 22 CONESTOGA-ROVERS & ASSOCIATES

impacted area. Groundwater was purged from temporary and permanent monitoring wells with the same procedures used for characterization sampling. However, Dr. Poreda also employed specific sample collection and containerization processes that are designed to minimize helium diffusion. The samples were then sent to the University of Rochester laboratory for specialty laboratory analyses. Further discussion on the sampling techniques, laboratory analyses methods, and the results of Dr. Poredas studies are in Appendix H. This appendix also provides background information and other references on the dating evaluation process.

016841 (12) 23 CONESTOGA-ROVERS & ASSOCIATES

5.0 DOCUMENTATION OF FIELD ACTIVITIES -

PRESENTATION OF STUDIES AND ANALYSES COMPLETED TO DATE This section provides a summary of regional and Site-specific geology and hydrogeology along with a discussion of vertical hydraulic gradients, groundwater elevations and flow directions, and overburden aquifer hydraulic conductivity in the Site area.

5.1 PHYSICAL SITE SETTING This section provides an overview of the surface and subsurface features of the Site area.

Discussions on regional and local hydrogeology are provided.

5.1.1 REGIONAL TOPOGRAPHY AND SURFACE WATER FEATURES The site is located within the Kankakee River Basin approximately ten miles from the confluence of the Kankakee River with the Illinois River (Figure 1.1). In general, the topography of the area slopes downward to the north toward the Illinois River.

5.1.2 REGIONAL GEOLOGY The regional geology is composed of a relatively thin overburden layer overlying the bedrock (see Figure 5.1). The overburden consists of a sand and gravel unit and a glacial till unit with some lenses of coarse-grained glacial drift. The important bedrock units can be divided into five general sections:

• Pennsylvanian age siltstone, shale, and coal;

• Silurian dolostone;

• Ordovician shale;

• Ordovician-Cambrian sandstone and limestone/dolostone; and

• Cambrian Eau Claire shale.

The Pennsylvanian age units are generally horizontal strata that act as an aquitard. The coal-bearing Carbondale Formation (Colchester Member) within this group was previously strip-mined in the area of the Site. The strip mining removed the overlying units to the bottom of this coal seam.

016841 (12) 24 CONESTOGA-ROVERS & ASSOCIATES

Beneath the Pennsylvanian siltstone and shale aquitard lies a Silurian-age dolostone aquifer. The Ordovician shale of the Maquoketa Shale Group separates this dolostone aquifer from the underlying Cambrian-Ordovician aquifers. The Maquoketa Shale Group consists of several shale and limestone units that act as an aquitard between the two bedrock aquifers.

The Cambrian-Ordovician aquifers beneath the Maquoketa Shale Group consist of two major sandstone aquifers, the Ancell aquifer (composed of the Glenwood Formation and St. Peter Sandstone) and the Ironton-Galesville aquifer (composed of the Ironton and Galesville Sandstones). Separating these two aquifers is a confining unit made up mainly of dolomite and shale with some sandstone. In general, these two units are considered to be one aquifer and are called the deep bedrock aquifer. The deep bedrock aquifer is an average thickness of 1000 feet and dips to the southeast (Visocky, 1985).

The Cambrian-age Eau Claire Formation acts as an aquitard that separates the deep bedrock aquifer from the Mt. Simon aquifer. The Mt. Simon Sandstone is not suitable for groundwater extraction due to poor water quality (Visocky, 1997).

5.1.3 REGIONAL HYDROGEOLOGY Groundwater in the region is mainly extracted from three aquifers:

• The sand and gravel overburden deposits;

• The shallow Silurian dolomite; and

• The deep sandstone and dolomite formations of Cambrian and Ordovician age.

There are several private wells screened within the surficial sand unit where well yields are highly variable. In general, yields range from 20 gpm to 100 gpm; the higher yields are in areas where the sand and gravel deposits are thickest. The recorded well yields in the Silurian-age dolostone aquifer are extremely variable, with yields over 1,000 gpm measured. In general, yields of less than 500 gpm are encountered most often (Schicht et al, 1976).

The most important aquifer in the region is the Cambrian-Ordovician Aquifer, which is also called the deep sandstone aquifer. The wells from this aquifer yield approximately 700 gpm. Figure 5.2 presents the groundwater elevations and regional groundwater flow direction in the bedrock aquifer. As shown, the groundwater in the region flows 016841 (12) 25 CONESTOGA-ROVERS & ASSOCIATES

toward Lake Michigan. Near the Site, this means that the regional groundwater flow in the deep bedrock aquifer is to the north-northeast (Schicht et al, 1976).

5.1.4 SITE-SPECIFIC TOPOGRAPHY AND SURFACE WATER FEATURES Figure 2.1 presents the relevant surface water features at the Site. The topography at the Site is generally flat, with a gentle slope to the north. Surface water drains toward the Exelon and northwest ponds, as well as toward the perimeter ditch.

5.1.5 SITE-SPECIFIC GEOLOGY The geology beneath the Site consists of a relatively thin overburden deposit that overlies alternating layers of shale/siltstone and dolostone. Figure 5.3 presents a generalized south-north geologic cross-section of the Site, and provides a general overview of the important lithologies of the subsurface.

The overburden at the Site consists of the Equality Formation (silty sand) and the Wedron Formation (glacial outwash and till). The Equality sand is the surficial unit and is described as a homogenous, loose, gray to brown sand in borehole logs completed at the Site. This formation is approximately 20 feet thick at the Site. The Wedron Formation consists of glacial till and interbedded discontinuous glacial outwash deposits. At the Site the Wedron Formation ranges from 15 to 20 feet thick. Figure 5.4 presents the top of the clay/till unit at the Site, which overlies the bedrock. The figure indicates that the clay unit generally dips to the north, generally following the overburden groundwater flow direction at the Site.

The bedrock at the Site is generally typical of the regional geology, with the exception that the Silurian dolostones are not present. The upper bedrock at the Site is encountered at approximately 40 feet below ground surface and consists of Pennsylvanian siltstone, shale, limestone and coal with a local water-bearing conglomerate. Strip mining south of the Site has removed the coal and the overlying units. The mined area has subsequently filled with water and is now a lake. The important features of the deeper stratigraphic units were presented in Section 5.1.2 and 5.1.3.

016841 (12) 26 CONESTOGA-ROVERS & ASSOCIATES

5.1.6 SITE-SPECIFIC HYDROGEOLOGY In general, there are two aquifers used for water supply near the Site. The first aquifer consists of the sand in the overburden, and the second aquifer is the Ordivician-Cambrian sandstone units of the deep bedrock aquifer.

The groundwater in the sand aquifer of the overburden occurs under unconfined (water table) conditions and ranges in thickness from 20 to 22 feet. The groundwater in this aquifer is recharged by local precipitation and discharges to local ponds and streams, and to the bedrock. Water well yields from this aquifer are suitable for domestic use, and range from 2 to 5 gpm (UFSAR, December 1988).

Over 155 monitoring wells have been installed into the deep and shallow zones of the overburden aquifer at the Site. Figure 4.1 presents the monitoring well network.

Several well nests have been installed in the overburden aquifer not only to determine the vertical distribution of impacted groundwater, but also the vertical hydraulic gradient within the aquifer. The calculated vertical hydraulic gradients at the Site are presented on Figure 5.5 and in Table 5.1. These data indicate that there is no systematic pattern of vertical hydraulic gradient at the Site.

Table 4.2 presents groundwater elevations. Figures 5.6 and 5.7 present the groundwater elevations and flow directions in the shallow and deep zones, respectively. The figures show that groundwater at the Site flows generally north-northwest in both zones of the aquifer. 6 The pattern of groundwater contours and the elevation of the water in Exelon Pond indicate that there is a significant interaction between the groundwater in the overburden and the water in the pond. Groundwater elevations south (upgradient) of the pond are higher than the pond elevation, indicating that groundwater discharges to the pond. The groundwater elevations measured north (downgradient) of the pond are lower than the pond level, indicating that surface water recharges the groundwater to the north. This has important implications for contaminant transport at the Site, because it indicates that impacted groundwater discharges to the pond, become mixed with unimpacted surface runoff, and then recharges to the groundwater at a significantly lower concentration.

The results from single-well response tests indicate that the hydraulic conductivity of the overburden aquifer is in the range of 2.5x10-2 cm/sec to 3.7x10-2 cm/sec (see Appendix F). The average horizontal hydraulic gradient in the overburden is 0.002.

6 The groundwater elevation near MW-106 is probably elevated beyond its normal level due to localized mounding caused by nearby ditches and the Cooling Lake.

016841 (12) 27 CONESTOGA-ROVERS & ASSOCIATES

Assuming an effective porosity of 0.3, average groundwater velocity in the overburden aquifer is 80 ft/yr. to 170 ft/yr. The shallow aquifer flow is more influenced by the recharge and surface water features at the Site, and therefore has the higher groundwater velocity; the deeper groundwater velocity is closer to the lower end of the range of values.

The Braidwood Station Cooling Lake, which is located on the upgradient side of the Site, is not in direct contact with the upper sand aquifer, but rather is separated by a slurry wall that was installed at the time the Braidwood Station was built. The slurry wall was installed into the Wedron clayey till unit. The Cooling Lake is surrounded by this slurry wall and is, therefore, isolated from the upper sand aquifer in all areas of the Braidwood Station property.

The overburden aquifer is separated from the deep bedrock aquifer by approximately 140 feet of relatively impermeable shales. The shale units act as aquitards, limiting the hydraulic communication between the groundwater in the overburden and the bedrock aquifer. Most domestic wells in the area are completed within the Glenwood-St. Peter Formation, which is approximately 600 feet below the ground surface.

As mentioned in Section 5.1.2, there is a history of open-pit coal mining in the region.

As a result of coal mining, there are several small lakes near the Site formed when abandoned open-pit mines subsequently filled with groundwater and precipitation. The Cooling Lake south of the facility is one of these lakes. Historical documents indicate the potential for abandoned mine shafts near the Site. In addition, a hand sketch provided by an adjacent landowner indicates the presence of a mine shaft and air shaft in property north of Smiley Road (see Appendix I). It is possible that these abandoned shafts could act as conduits for impacted water to infiltrate into the water-bearing units immediately underlying the Wedron till (Carbondale Channel Sandstone) and immediately overlying the coal seam (Carbondale conglomerate). The coal seams are found at depths of approximately 100 feet bgs. All of the currently available relevant information regarding mining shafts in the area is in Appendix I. Further evaluations of the influence of these historical mining operations on shallow groundwater is presented in Section 6.4.

016841 (12) 28 CONESTOGA-ROVERS & ASSOCIATES

6.0 DESCRIPTION

OF THE CHEMICALS OF CONCERN AND SOURCE AREAS This section presents an evaluation of the source of tritium, its fate in the subsurface, and its distribution in groundwater.

6.1 GENERAL TRITIUM CHARACTERISTICS Tritium (chemical symbol 3H ) is a radioactive isotope of the element hydrogen. Tritium is produced naturally in the upper atmosphere when cosmic rays strike air molecules.

Tritium is also produced during nuclear weapons explosions, as a byproduct in reactors producing electricity, and in special production reactors, where the isotopes lithium-7 and/or boron-10 are bombarded to produce tritium.

Although tritium can be a gas, its most common form is in water because, like non-radioactive hydrogen, radioactive tritium reacts with oxygen to form water.

Tritium replaces one of the stable hydrogen atoms in the water molecule and is called tritiated water. Like H2O, tritiated water is colorless and odorless. Tritiated water behaves chemically and physically like non-tritiated water in the subsurface, and therefore a plume of tritiated water will travel at the same velocity as the average groundwater velocity.

Tritium has a half-life of approximately 12.3 years. It decays spontaneously to helium-3 (3He). This radioactive decay releases a beta particle (high-energy electron). The radioactivity of tritium is the source of the risk of exposure. The United States Environmental Protection Agency (USEPA) has established a Maximum Contaminant Level (MCL) of 4 millirem per year for beta particles and photon radioactivity from man-made radionuclides in groundwater. This standard applies to public water supplies (40 CFR 141.1). The average concentration of tritium that is assumed to yield 4 millirem per year is 20,000 pCi/L. If other radionuclides that emit beta particles and photon radioactivitiy are present in addition to tritium, the sum of the annual dose from all the radionuclides shall not exceed 4 millirem/year.

Tritium is one of the least dangerous radionuclides because it emits very weak radiation and leaves the body relatively quickly. Since tritium is almost always found as water, it goes directly into soft tissues and organs. The associated dose to these tissues is generally uniform and is dependent on the water content of the specific tissue.

Under normal operating conditions at the Braidwood Facility, tritium is the principal radionuclide discharged from the plant. Tritium is formed when boron and/or lithium 016841 (12) 29 CONESTOGA-ROVERS & ASSOCIATES

atoms present in the reactor coolant capture a neutron. Exelon periodically releases excess plant water that contains tritium to the Kankakee River through the blowdown line.

Tritium in the groundwater at the Site therefore has two sources: tritium in infiltrating precipitation (background) and tritium from leaks from the vacuum breakers in the blowdown line. Background tritium concentrations in groundwater is roughly 200 pCi/L. These background values are discussed in more detail in Section 7.0.

6.2 CHARACTERISTICS OF WATER IN THE BLOWDOWN LINE - COOLING LAKE WATER QUALITY Braidwood generating station uses a cooling lake to provide a heat sink for its main condensers. Since the lake is warm and has a large surface area (over 2,800 acres), it loses much of its water to evaporation. This evaporation causes the concentration of dissolved and suspended minerals in the lake to increase.

Table 6.1 presents a comparison of the general chemistry of cooling water samples and samples from unimpacted groundwater wells. Appendix J presents the laboratory reports for these analyses. CRA compared Cooling Lake (blowdown line) samples at the facility and at the outfall to the Kankakee River to groundwater samples collected from MW-106D and MW-110. As shown in Table 6.1, the chemistry of the cooling water is generally consistent. More specifically, the concentrations of both chloride and sodium in the cooling water are significantly higher than in the groundwater samples. There are differences in the concentrations of other parameters between the cooling water and the groundwater, but the most significant differences are the chloride and sodium concentrations. Therefore, CRA used sodium and chloride as indicators of cooling water impact to the groundwater in the absence of tritium values. These data also show that the concentrations of metals and general chemistry parameters in the cooling water do not exceed applicable groundwater standards.

In addition to tritium and general chemistry sampling, Exelon has sampled the groundwater at monitoring wells for other radionucleides. These data are in Appendix D. The results indicate that none of the radionucleides exceeded the lower limit detection in groundwater. Therefore, the only contaminant of concern in the groundwater at the Site is tritium.

016841 (12) 30 CONESTOGA-ROVERS & ASSOCIATES

6.3 DISTRIBUTION OF TRITIUM IN GROUNDWATER AT THE SITE Figures 6.1 and 6.2 present the estimated horizontal distribution of tritium in the shallow and deep overburden zones, respectively. The figures show that the highest tritium concentrations are near VB-2 and VB-3, supporting the conclusion that these two vacuum breakers are the source of the tritium. The groundwater plume extends north and west from this area toward Exelon Pond. As the figures clearly show, concentration northwest of the pond is considerably lower. This indicates the plume is being diluted by the pond.

There is a smaller source near VB-1, which is immediately east of the facility. As shown on Figures 6.1 and 6.2, tritium concentrations in this area are much lower than in the area north of VB-2 and VB-3. The concentrations of tritium decrease quickly to background levels downgradient of VB-1.

Figures 6.1 and 6.2 indicate that tritium concentrations are somewhat higher in the deep zone relative to the shallow zone. This is attributed to precipitation infiltration. After the impacted groundwater begins to migrate away from the source area, infiltrating precipitation not only forces the impacted water deeper into the aquifer, but also dilutes the impacted water at the water table. Maximum tritium results are presented on Figures 6.3 and 6.4 for the shallow and deep overburden, respectively, and in Table 6.2.

The data shows that the maximum extent of the tritium plumes are consistent with those shown on Figures 6.1 and 6.2.

Figure 6.5 presents the locations of two hydrogeologic cross-sections at the Site.

Hydrogeologic cross-sections A-A' and B-B' are presented on Figures 6.6 and 6.7, respectively. Figure 6.6 presents a cross-section along the groundwater flowpath from the Cooling Lake to northeast of the off-Site pond. Figure 6.7 presents a cross-section perpendicular to groundwater flow near the blowdown line. Both figures indicate that the greatest tritium values are at depth. However, the Wedron Formation clay till and the underlying shales act as aquitards, limiting the hydraulic communication between the groundwater in the overburden and the bedrock aquifer.

Using the most recent groundwater results, CRA calculated the mass of tritium in the overburden groundwater. The mass of tritium in the groundwater was determined at vacuum breakers VB-1 and at VB-2 and VB-3 (combined), with results of 0.19 Curies (Ci) and 2.05 Ci, respectively, or 2.24 Ci total on Site. The tritium mass was calculated by measuring the area the plume covers in the deep and shallow groundwater zones (Figures 6.1 and 6.2). The data are in Appendix K.

016841 (12) 31 CONESTOGA-ROVERS & ASSOCIATES

Periodic tritium analyses have been performed at selected locations at the Site to determine the variability in the data. In general, samples were collected weekly at each location. The locations involved in the periodic sampling program are presented on Figure 4.1, and the tritium results are presented in Table 6.3. Specifically, samples have been collected routinely at groundwater monitoring locations P-4, P-4D, P-13D, BL-9, BL-9D, S-2, S-2D, C-2, and C-2D, and at surface water sample locations SW-2 and Alpha Gate (on the perimeter ditch north of VB-1).

Appendix D shows tritium concentrations and groundwater elevations over time for the weekly sampling locations. The weekly tritium results indicate that tritium concentrations fluctuate over time, and the concentrations tend to vary with the groundwater elevation. In general, the tritium concentrations show a negative correlation with groundwater elevation in the locations south of Exelon pond (P-4, P-4D, P-13D, BL-9, and BL-9D on Figure D.1 of Appendix D), and a positive correlation with groundwater elevation in the locations north of Exelon Pond (S-2, S-2D, C-2, and C-2D on Figure D-2 of Appendix D). The negative correlation south of the pond is likely due to the fact that the increase in water level is from (non-tritiated) infiltrating water diluting the groundwater tritium. The tritium concentrations in the locations north of the pond are much closer to ambient atmospheric values in the area (200 pCi/L). This means that the precipitation infiltrating to the ground (raising the groundwater level) may have higher tritium concentrations than the groundwater and therefore tritium concentration increases with the increase in infiltrating water. The tritium concentrations in the surface water locations (SW-2 and Alpha Gate) fluctuate over time but do not appear to have a significant trend over time.

Groundwater samples from the private wells PW-10 and PW-11, which are completed in the deep bedrock north of the Site, indicate that tritium is at or below the background concentration in the deep bedrock aquifers. Samples from the private wells PW-7, PW-9, PW-14, and PW-15, which are completed in the channel sandstone deposits or the conglomerate, indicate that tritium is also below the background concentration in the channel sandstone deposits and the conglomerate. Maximum tritium results in all the private wells on site are presented in Figure 6.8 and in Table 6.4.

6.4 CONCEPTUAL MODEL OF TRITIUM RELEASE AND MIGRATION This section summarizes the current understanding of the mechanism for tritium releases to the groundwater at the Site and presents the conceptual model.

016841 (12) 32 CONESTOGA-ROVERS & ASSOCIATES

The historical data indicate that there were several releases of tritiated water from the vacuum breakers. In each case, water from the blowdown line was released to the surface and downward into the subsurface.

The surface releases from VB-2 and VB-3 flooded the low-lying area between the valves and Smiley road. The area that flooded is bounded by the mounded dirt covering the blowdown pipe on the east and south, Smiley Road to the north, and an estimated 300-400 feet to the west. The exact westerly boundary is not known but is estimated based on the topography of the area. This is generally the area where the most concentrated part of the groundwater plume is detected today. Releases from VB-1 flowed in groundwater toward the Site perimeter ditch.

The observations of Station personnel and the construction of the vacuum breaker valve vaults (valve pits) both suggest that water was not only released to the ground surface but also discharged vertically downward into the groundwater table. The vacuum breaker vaults are round concrete vaults or valve pits which extend down to the top of the blowdown line. There is no sealed bottom on these round concrete structures in order to allow access to the valve extending off the main blowdown pipe and to allow access to the pipe itself. The bottom of the vacuum breaker vaults is filled with gravel to allow the shallow water table to come into the vault under high water table conditions and to allow collected water to drain out the bottom. Therefore, when the valve failures occurred, most of the water released would have flowed downward within the vacuum breaker vault and recharged the water table through the bottom. Consequently, most of the blowdown line water was released to the subsurface as well as to the land surface in releases from the vacuum breakers.

The groundwater data collected also support the mechanism that a significant component of flow from releases was downward into the vacuum breaker vault (valve pit). Under this scenario, a portion of the tritium released from the vacuum breakers entered the groundwater near the vacuum breaker location and then traveled with groundwater at the estimated velocity of 80 ft/yr. to 170 ft/yr. In a sense, the vacuum breaker vaults would act as dry wells to allow the tritium to enter the groundwater (vertically) at a rate faster than normal subsurface infiltration.

There is evidence of this downward migration pathway in the detections of blowdown line indicators or fingerprints (sodium, chloride and tritium) at a few of the deeper temporary wells installed downgradient of VB-2 and VB-3, specifically, at BL-9D and BL-10D located near VB-2 and the deeper temporary wells located 300 to 500 feet downgradient (north-northwest) of VB-3. In the case of VB-3, the subsurface 016841 (12) 33 CONESTOGA-ROVERS & ASSOCIATES

mechanism occurred for a short time and allowed elevated levels of tritium to enter into the groundwater instantaneously, and then the discharge stopped.

The overland flow of water resulted in the source areas from each release extending much further downgradient than would be expected if the impacted water was only released directly to the groundwater at the blowdown line. This pattern of tritium appears to mimic what would have occurred for a continuous leak if the blowdown line was responsible for the tritium in the groundwater. Other evidence shows that continuous release is not the case, however. The tritium dating results are inconsistent with a slow continuous leak in the blowdown line (see Appendix H). Tritium dates in the deep overburden near the blowdown line are consistent with a leak that occurred in or around 2000. As described in the Poreda report, the shallow groundwater tritium date is consistent with diffusion of helium from deeper groundwater, but not with a recent release.

Exelon also collected groundwater samples adjacent to the blowdown line (near VB-2) to determine if the pipe was leaking. These groundwater samples were analyzed for tritium, sodium, and chloride. These results, which are presented in Table 6.5, indicate that the concentrations are similar to those in the background wells. This means that there is no continuous leak from the blowdown line near VB-2 and that the release was from the vacuum breaker failures.

The surface area of the plume and maximum distance from VB-2 and VB-3 (approximately 2,600 feet) gives the appearance that the releases occurred prior to 1998 if groundwater flow velocity is approximately 80 ft/yr. to 170 ft/yr. This is also somewhat misleading because the groundwater discharges to and mixes with Exelon Pond. In effect, the impacted water takes a "short cut" in the pond and, therefore, travels much further and faster than under normal groundwater flow conditions.

This rapid migration is supported by the groundwater contours that indicate a strong influence from the pond (Figures 5.6 and 5.7) and is also supported by the tritium dating data. These results for the water north of the pond indicate that the starting dates of the water were reset by equilibration with the atmosphere. This equilibration with the atmosphere could only have occurred in the pond, and therefore the tritiated water must be mixing with the surface water, releasing its 3He. This mixing not only has the effect of rapidly moving the impacted water further downgradient (to the north side of the pond), but also reducing the tritium concentration through dilution.

Despite the fact that the release at VB-1 occurred before those at VB-2 and VB-3, the plume at VB-1 is much smaller. This is because the release at VB-1 was smaller than the 016841 (12) 34 CONESTOGA-ROVERS & ASSOCIATES

other releases. It is also likely due to the fact that much of the shallow groundwater, which is migrating north from VB-1, is being intercepted by the perimeter ditch. A small portion of the tritiated groundwater discharges to the ditch and is carried off Site to the west. The deeper groundwater plume appears to be much smaller than expected based on its age and concentration, which may indicate that the ditch is also intercepting some of the deeper water.

The historical mining operations in the area (Appendix I) present the possibility that abandoned shafts or old exploration borings may act as conduits to the deeper water-bearing bedrock layers. However, the groundwater contours at the Site do not show any areas where this is occurring. Further, the chemistry from the private wells in the area do not contain concentrations of tritium that exceed background levels. In summary, based upon existing Site data the primary migration pathway of tritium has been laterally through the shallow sand aquifer from the north to the south and not downward into deeper hydrogeologic units.

016841 (12) 35 CONESTOGA-ROVERS & ASSOCIATES

7.0 ENDANGERMENT ASSESSMENT This Section of the report addresses the releases from the Recognized Environmental Conditions (the failed vacuum breakers) and any potential risks to human health and the environment. The intent of this section is to describe the potential risks from any completed exposure pathways.

In summary, based upon historical knowledge and data of the Braidwood Station operations and based upon chemical analyses in the blowdown line and in groundwater samples, the only Chemical of Concern is tritium. The discussions that follow are focused on the exposure pathways related to tritium.

7.1 HEALTH EFFECTS OF TRITIUM Tritium is a radioactive isotope of hydrogen. The most common forms of tritium are tritium gas and tritium oxide, which is also called tritiated water. The chemical properties of tritium are essentially those of ordinary hydrogen. Tritiated water behaves the same as ordinary water in both the environment and the body. Tritium can be taken into the body by drinking water, breathing air, eating food, or through skin absorption.

Once tritium enters the body, it disperses quickly and is uniformly distributed throughout the body. Tritium is excreted from the body through the urine, with a biological half-life of 10 days, the same as for water.

A person's exposure to tritium is primarily through the ingestion of water (drinking water) or through ingestion of waterbearing food products. Inhalation of tritium requires the water to be in a vapor form (i.e., through evaporation or vaporization due to heating). Inhalation is a minor exposure route when compared to direct ingestion or drinking of tritiated water. Absorption of tritium through the skin is possible, but tritium exposure is more limited here versus direct ingestion or drinking of tritiated water.

Tritium is weakly radioactive. It decays by emitting a low-energy beta particle that cannot penetrate deeply into tissue or travel far in air. It poses a potential health hazard only if it is taken into the body. The beta particle emitted by tritium when it decays is a form of ionizing radiation. For radiation protection purposes, all radiation exposure is considered to increase the risk of developing cancer, and the risk is considered to be proportional to dose, even at low levels for which there is no conclusive scientific evidence of radiation effects.

016841 (12) 36 CONESTOGA-ROVERS & ASSOCIATES

The EPA considers tritium to be one of the least dangerous radionuclides because it emits very weak radiation and leaves the body relatively quickly. Since tritium is almost always found in water, it goes directly into soft tissues and organs. The associated dose to these tissues is generally uniform and dependent on the tissues' water content.

Tritium does not concentrate in any one organ; therefore, the dose is spread through the entire body.

7.2 GROUNDWATER STANDARD The ingestion of tritium through drinking of potable water is a potential exposure route at this Site (refer to Section 8.4). Currently, the IEPA relies on a USEPA groundwater standard for tritium of 20,000 pCi/L (35 IAC 620 Section 410 (e)). The following is the basis of this standard per this section of the Act:

Beta Particle and Photon Radioactivity Except due to natural causes, the average concentration of beta particle and photon radioactivity from man-made radionuclides shall not exceed a dose equivalent to the total body organ greater than 4 mrem/year in Class I groundwater. If two or more radionuclides are present, the sum of their dose equivalent to the total body, or to any internal organ shall not exceed 4 mrem/year in Class I groundwater except due to natural causes.

Except for the radionuclides listed in subsection (e)(3), the concentration of man-made radionuclides causing 4 mrem total body or organ dose equivalent must be calculated on the basis of a 2 liter per day drinking water intake using the 168-hour data in accordance with the procedure set forth in NCRP Report Number 22, incorporated by reference at Section 620.125(a).

Except due to natural causes, the average annual concentration assumed to produce a total body or organ dose of 4 mrem/year of the following chemical constituents shall not be exceeded in Class I groundwater:

Critical Standard Constituent Organ (pCi/L)

Tritium Total Body 20,000 Strontium-90 Bone Marrow 8 016841 (12) 37 CONESTOGA-ROVERS & ASSOCIATES

Thus, the concentration of tritium in groundwater should not exceed the 20,000 pCi/L level at a potable water supply. Tritium concentrations that will protect human health are less than 20,000 pCi/L. CRA uses this standard for comparison purposes, comparing the analytical results presented in this report to the standard.

The surface water quality criteria for tritium (20,000 pCi/L) is based upon the same evaluation presented above as it addresses the ingestion and absorption exposure routes during recreational use of general resource surface water bodies. This standard is used herein for comparison purposes. Exelon will develop Site specific objectives under separate cover as discussed in Section 9.3.

7.3 SITE SPECIFIC BACKGROUND CONCENTRATIONS OF TRITIUM IN GROUNDWATER At the Braidwood Station, the background, or ambient, concentrations of tritium in the groundwater occur where there have been no releases. Specifically, background concentrations should occur in those areas of the shallow sand aquifer that are either upgradient of the vacuum breakers or downgradient but outside the plumes. Based on these criteria, the background concentration is 200 pCi/L. This conclusion is based upon a number of evaluations and assessments.

Dr. Robert Poreda, University of Rochester, who is an expert in the field of tritium dating, indicated that his testing in Nebraska and Wisconsin showed typical background values of 100 pCi/L. However, the background at Braidwood would likely be slightly higher given its location downwind of the Quad Cities, LaSalle, and Dresden Nuclear power plants. According to Dr. Poreda, the upper limit for rainfall he has measured is 200 pCi/L.

In addition, information on background concentrations of tritium in groundwater were obtained from a Michigan Department of Environmental Quality study. 7 According to this study, concentrations in Michigan groundwater today may be on the order of 160 to 320 pCi/L. Consequently, the assumption that background at the Site is 200 pCi/L is reasonable.

Finally, the laboratory that is currently performing the analysis of tritium in the groundwater samples collected at this Site has a lower limit of detection of 200 pCi/L.

This is a practical quantification limit above which the laboratory has confidence in their 7 Use of Tritium in Assessing Aquifer Vulnerability" available at http://www.deq.state.mi.us/documents/deq-dwrpd-gws-wpu-Tritium.pdf 016841 (12) 38 CONESTOGA-ROVERS & ASSOCIATES

quantitative estimate. Any result below this concentration is an estimate. The estimated values provided by the laboratory are still, nevertheless, at concentrations that are less than the 200 pCi/L background at this Site.

7.4 EXPOSURE ROUTE EVALUATIONS The potential exposure point pathways and potential receptors for tritium that was released from the three vacuum breakers (VB-1, VB-2, and VB-3) are discussed in the following sections. CRA has identified any incomplete and complete exposure pathways.

7.4.1 IDENTIFICATION OF POTENTIAL EXPOSURE PATHWAYS AND POTENTIAL RECEPTORS There are two mechanisms for tritium in the blowdown line water to reach the groundwater from the failed vacuum breakers:

• Direct discharge from the valve into the valve vault and downward into the groundwater table; and

• Overflow of the water from the top of the vault, through the manhole, and onto the land surface. Subsequently, the ponded water infiltrates downward to the water table.

7.4.1.1 DIRECT DISCHARGE SCENARIO The complete exposure routes or pathways for tritium migration to potential receptors for the first scenario, direct discharge to the groundwater, include:

1.1 Groundwater flow to the north (downgradient direction) to private water supply wells; 1.2 Groundwater flow to the north and subsequent discharge into the ponds north of Smiley Road; and 1.3 Groundwater flow to the north from VB-1 and into the perimeter ditch, which then flows north and west.

016841 (12) 39 CONESTOGA-ROVERS & ASSOCIATES

Under the first release scenario, direct discharge to the groundwater from the vacuum breaker, the potential receptors include off-property users of the shallow sand aquifer and recreational users of the northern off-Site ponds. In addition, there could be a potential worker exposure to tritium in the perimeter ditch, which is on Exelon's property.

7.4.1.2 OVERFLOW SCENARIO The complete exposure routes or pathways for tritium migration to potential receptors for the second scenario, overland surface flow, include:

2.1 Direct contact with standing or ponded water on the Braidwood Station Property at the time of the spill; 2.2 Seepage into the underlying vadose zone and into the groundwater; 2.3 Direct contact with surface water ponded at the time of the spill in the ditch south of Smiley Road; 2.4 Groundwater flow to the north (downgradient direction) to private water supply wells; 2.5 Groundwater flow to the north and into the ponds north of Smiley Road; and 2.6 Groundwater flow to the north from VB-1 and into the perimeter ditch, which then flows north and west.

Under the second release scenario, the potential receptors include Braidwood Station workers, contact with surface water ponded in the ditch on the south side of Smiley Road, off-property well users, and recreational users of off-property ponds. Also, there is the potential scenario where a worker could be exposed to tritium in the perimeter ditch. These potential receptors and the identified exposure routes are discussed in the following sections.

The water would be ponded or pooled on the surface before it seeped into the underlying soils. There is approximately 5 to 8 feet of unsaturated soils (vadose zone) above the water table. The ponded water would seep through these soils to the water table. As such, a small percentage of this water would initially remain in the soils above the water table after the spill. However, since tritium has characteristics of water it will not sorb onto the soil particles. Rather, it will remain as part of the residual water left in the soil pores. This residual tritium will eventually be flushed downward to the water 016841 (12) 40 CONESTOGA-ROVERS & ASSOCIATES

table. The infiltration of rain or snow melt will reduce the residual saturation by two methods: 8

• Flushing of pore water with tritium out of the soil column into the underlying water table; and

• Dilution of the residual tritium levels with recharge.

The likelihood of the unsaturated soils containing significant levels of tritium in pore water over any extended period is unlikely. The reduction of any residual tritium in the soil column should be rapid given the approximately 12 inches of precipitation recharge each year in Illinois (35 IAC 742). As such, the expected concentration of tritium in the soil column should be in the range of ambient concentrations for rain water (160 to 320 pCi/L) 9 and significantly below the groundwater standard (20,000 pCi/L).

Given the physical conditions with regard to residual tritium in the soil column; this exposure pathway is incomplete. Direct contact with tritium in soils beneath the former spill areas 10 is not a complete pathway because:

• This area is within the boundaries of the Braidwood Station property and, therefore, access is restricted to Exelon employees;

• This is not an active, operational area of the facility and as such subsurface excavations or other construction work is not performed that might expose workers to the subsurface soils; and

• Braidwood Station excavation protocols would require health and safety monitoring and preventative measures to eliminate exposure to soils that might have unsafe radiological conditions.

In summary, the soil exposure route to tritium in the Site area is incomplete.

Once in the groundwater, the tritium will migrate to the north with groundwater flow away from the vacuum breakers. There is no exposure route for the ingestion of groundwater on Exelon's property. The Station receives its potable water from the Kankakee River (approximately 5 miles east of the Site). In addition, Exelon's property is considered an industrial property, and existing zoning and other institutional controls 8 These mechanisms apply both to the water that ponded on the Braidwood Station property and to the water that ponded in the small ditch south of Smiley Road.

9 Use of Tritium in Assessing Aquifer Vulnerability, http://www.epa.state.il.us/water/tritium.html, Illinois Environmental Protection Agency, Bureau of Water, October 1997.

10 Including the small ditch south of Smiley Road.

016841 (12) 41 CONESTOGA-ROVERS & ASSOCIATES

would prevent the installation of potable water supply wells on the property. Therefore, there is no complete exposure route for groundwater ingestion on Exelon's property.

Groundwater containing tritium will migrate to the north (downgradient) of Exelon's property and onto adjacent private property. There are a number of private land owners to the north where the residential water supply is provided by private wells completed in the shallow sand aquifer. These shallow water supply wells are considered potential pathways. The land that is directly north of Smiley Road (where the Exelon Pond is located) is owned by the Braidwood Station. As such, the small area where there are exceedences of the groundwater standard does not have potable water wells in the shallow sand aquifer. However, migration of tritiated groundwater farther to the north of this is a potential exposure pathway.

Currently, there are no private water supply wells with tritium that exceed the groundwater standard. In addition, no private property contains groundwater with tritium at a concentration that exceeds the groundwater standard. These observations are based upon a wealth of groundwater data collected as part of this study.

To evaluate future conditions, CRA modeled the potential migration of the existing tritium located south of Smiley Road to the property to the north. BIOSCREEN, a USEPA analytical model, assessed the migration of tritium found within the main "plume" area south of Smiley Road. Appendix L presents the data used, the assumptions made, and the results of the analytical simulations. Figure 7.1 presents a graphical representation of the BIOSCREEN modeling for tritium. This figure depicts the shape of the extent of migration of the tritium from the area south of Smiley Road toward the north. Even with very conservative assumptions, the BIOSCREEN model predicts that tritium concentrations in groundwater under private property north of Smiley Road will not exceed the groundwater standard. Consequently, future exposure of private well users to tritium concentrations that exceed the groundwater standard is also incomplete. As a result of this modeling, Exelon concluded that no additional well owners require notification of potential impact to their wells.

The water well inventory, discussed in Section 4.3 and provided in Appendix G, indicates that there are a number of private and public (Village of Braidwood) water supply wells that are completed in the deep regional aquifer. These deep aquifers are found at depths of 100 to 1,600 feet bgs. Exelon has sampled 10 private water supply wells completed in the deeper aquifers and analyzed the groundwater as part of this investigation (see Figure 2.2 for the location of the deeper wells). For example, private wells PW-10 and PW-11 are downgradient of the main area of tritium-impacted groundwater. As can be seen in Appendix G and on Figure 6.8, these deeper wells did 016841 (12) 42 CONESTOGA-ROVERS & ASSOCIATES

not contain tritium that exceeded background. This is to be expected because the vertical movement of tritium into deeper formations is restricted by the following three regional aquitards (refer to Figure 5.1):

• The Wedron Formation of clayey till, which directly underlies the upper sand aquifer;

• The shales of the Carbondale Formation and the Spoon Formation; and

• The Scales Shale of the Maquoketa Group.

These three layers represent regional vertical barriers to groundwater flow. Moreover, the presence of these barriers eliminates the potential for tritium to migrate to the deep bedrock aquifers; therefore, the exposure pathway to deep bedrock water supply wells is incomplete.

It is possible that the former coal mining activities could have breached the shallower of the regional aquitards (Wedron Formation). Mining activities such as mine shafts, airshafts, and exploration holes would not have, however, breached the 70 to 80 feet thick Scales Shale Formation. This shale is found at a depth of over 200 feet bgs beneath the Site. Consequently, the Scales Shale would be a barrier to vertical groundwater flow to the regional aquifers. Again, the assertion that this pathway is functionally incomplete is supported by the results of sampling deeper bedrock wells. Tritium was not detected above background levels in any of these deeper wells.

Tritium has been found in surface water at the Site on three occasions. The first occasion was during the actual releases from the individual vacuum breakers when the water ponded on the land surface for a short time on the Braidwood Station property. 11 The second situation occurred when groundwater, containing tritium, discharged to the pond to the north of Smiley Road. The third situation occurred, in the case of the VB-1 area, when groundwater flowed into the perimeter ditch.

In the first situation, the potential for exposure no longer exists because the ponded water has seeped into the underlying soils and into the groundwater. The depth to the groundwater is at least 5 to 8 feet bgs at the Site. It is very unlikely that the water table will rise above the ground surface and create a surface water situation in the future.

Consequently, worker exposure (direct contact) on the Braidwood Station property to water ponded on the land surface is not possible. In addition, any further exposure beyond the initial ponding of water in the ditch to the south of Smiley Road is 11 And to some extent in the ditch located south of Smiley Road.

016841 (12) 43 CONESTOGA-ROVERS & ASSOCIATES

non-existent for the same reason. Any surface water in this ditch currently represents normal street run-off from the adjacent roadway and surrounding areas.

The second situation involves the transport of elevated levels of tritium in groundwater off the Braidwood Station property and into the pond to the north of Smiley Road. The pond is on private property, 12 has been used for recreational purposes in the past, and can be anticipated to be used for recreational purposes in the future. Therefore, there is a potential for direct contact and ingestion exposure to tritium by recreational users of this pond.

The third scenario involves the flow of tritium in groundwater from VB-1 into the perimeter ditch that flows to the north. The perimeter ditch is located within the boundaries and fence line of Exelon's property. As such, the only exposure would be worker exposure (direct contact) during maintenance or monitoring activities.

7.5

SUMMARY

OF EXPOSURE ROUTES In summary, there are three complete exposure routes for tritium:

• Groundwater ingestion by private well users when the wells are completed in the shallow sand aquifer;

• Recreational users of the ponds north of Smiley Road; and

• Braidwood Station workers involved with maintenance and monitoring of the perimeter ditch.

At this time, based upon the wealth of groundwater and surface water data provided in this report, none of the receptors at the above exposure points are at risk. The concentration of tritium in the groundwater or surface water at any of these three exposure points is significantly below the 20,000 pCi/L standard for groundwater.

Specifically, there is no private property in the Site area with a groundwater concentration of tritium that exceeds the groundwater standard (20,000 pCi/L) in the shallow sand aquifer 13 . The surface water samples collected from Exelon pond 14 and the 12 The pond directly north of Smiley Road (Exelon Pond) is on property recently purchased by Exelon and is now part of the Braidwood Station property. Exelon is constructing a fence to prevent use of the pond for recreational purposes, and the land will have its deed restricted to prevent the use of groundwater for potable purposes.

13 There is an area at the southeast corner of the pond directly north of Smiley Road that contains tritium that exceeds the groundwater standard. However, Exelon owns this land and restrictions are in place to prevent the installation and use of shallow wells on this property.

016841 (12) 44 CONESTOGA-ROVERS & ASSOCIATES

other nearby ponds to the northwest and northeast have not contained tritium that exceeds the 20,000 pCi/L groundwater criteria. Likewise, concentrations of tritium measured in surface water samples from the perimeter ditch as it flows off the Site have all been at levels less than the 20,000 pCi/L groundwater criteria. In summary, although there are three potentially complete exposure routes for tritium migration from the RECs (historic vacuum breaker releases), there has not been an exposure to those receptors.

Further, predictive calculations indicate that there will not be an exposure to these receptors in the future.

14 This pond is currently owned and controlled by Braidwood Station.

016841 (12) 45 CONESTOGA-ROVERS & ASSOCIATES

8.0 CONCLUSION

S The purpose of this report is to provide the IEPA a summary of Site characteristics as they relate to the sources, migration pathways, and extent of tritium in groundwater at the Braidwood Station Site.

Based on all of the studies completed to date, CRA concludes:

• Groundwater use in the Site area is both in the upper shallow sand aquifer (20 to 30 feet deep) and in the deeper bedrock formations used regionally for municipal and private water supplies (depths of 600 to 1,700 feet).

• The upper, shallow groundwater flows beneath the Site in a generally south to north manner, flowing from the Cooling Lake toward the ponds located north of the Braidwood Station property.

• Depth to water in this upper shallow sand aquifer ranges from 5 to 15 feet. The deeper bedrock water supply aquifers are separated from the shallow system by a number of regionally identified aquitards.

• Braidwood Station employs the blowdown line to return water from the Cooling Lake back to the Kankakee River. This blowdown line also serves as a permitted discharge point for the Station's sewage treatment plant and liquid radwaste system.

• The discharges from liquid radwaste contain tritium.

• Historical failures at the three vacuum breaker valves (VB-1, VB-2, and VB-3) have resulted in the release of tritium to the groundwater at this Site. The distributions of tritium in groundwater at this Site are consistent with historical releases from these three subject vacuum breakers.

• There are two localized areas on the Site where tritium is detected above the groundwater standard (20,000 pCi/L). The first area is south of Smiley Road and downgradient of VB-2 and VB-3 is approximately 4.5 acres. The second area is north of VB-1 and is less than 2.0 acres.

• Tritium above the background or ambient concentration (assumed to be 200 pCi/L in this study) has migrated into, and through, the pond located north of Smiley Road. The distance to the leading edge of the tritium plume (above the ambient concentration) from the source (VB-2 and VB-3) is approximately 2,400 to 2,800 feet.

• Deeper private water supply wells that are downgradient of the main tritium plume contain ambient concentrations of tritium. Regional aquitards act as vertical barriers to migration of tritium from surficial aquifers to deeper bedrock aquifers. This finding is consistent with an understanding of vertical groundwater flow.

016841 (12) 46 CONESTOGA-ROVERS & ASSOCIATES

• There are three complete exposure routes, or pathways, for tritium migration at the Site involving the following receptors:

• Groundwater ingestion by private well users

• Recreational users of the ponds

• Braidwood Station workers

• At this time, based upon the wealth of groundwater and surface water data provided in this report, none of the above receptors are at risk.

• A BIOSCREEN model (a future migration analysis) indicates that even under conservative assumptions, the elevated concentrations of tritium will not migrate to private property at levels that exceed the groundwater standard.

In summary, CRA believes that the information collected to date is sufficient to develop future documents to support remediation of the Site. The nature of the sources, the extent of the contamination, the fate and transport of the contamination, the identification of complete exposure routes and receptors, and the future potential for migration have been well characterized.

The studies performed to date are sufficient to begin remedial action planning and develop remedial objectives. There are, however, some minor data gaps that need to be filled as part of the remedial action planning process. These requirements are clearly stated in the next section.

016841 (12) 47 CONESTOGA-ROVERS & ASSOCIATES

9.0 PLAN OF ACTION The following discussion presents a plan of proposed activities intended to be completed in the near future.

9.1 FILL DATA GAPS There are no significant data gaps with regard to characterization. However, there are some items that need to be addressed to better define potential remedial actions. For instance, additional water level and tritium data collection within and around the perimeter ditch would be useful for developing controls to prevent further tritium migration. Also, additional water level monitoring near the pond north of Smiley Road will be helpful in understating the hydraulics of the pond and its use in a remedial action. The pond north of Smiley Road has been instrumented with a pressure transducer to continuously monitor the water levels.

9.2 GROUNDWATER MONITORING Exelon will prepare a plan to install new monitoring wells and abandon temporary wells. In addition, this plan will outline the frequency of monitoring and analyses for the permanent monitoring well network. Trigger levels of tritium concentrations will be developed and discussed in this plan. Eventually, this plan will be integrated with the remedial action selected for the Site and its operation and monitoring requirements.

Exelon will install permanent 2-inch diameter monitoring wells to be part of the long term, routine, groundwater monitoring program. Some temporary wells will be plugged and abandoned.

9.3 REMEDIATION The tritium concentrations in groundwater and surface water at the Site were compared to the 20,000 pCi/L standard provided in 35 IAC 620 Section 4.10 (e). This standard is for a Class I groundwater as characterized by 35 IAC 620 Section 210. The groundwater in the shallow sand aquifer is considered a Class I aquifer based upon its hydraulic properties and its use as a potable water supply in the Site area.

016841 (12) 48 CONESTOGA-ROVERS & ASSOCIATES

Exelon will prepare a Remedial Objectives Report (using the guidance provided 35 IAC 740), which will be used to develop a Remedial Action Plan (RAP) for this Site.

CRA anticipates that procedures presented in the Tiered Approach to Corrective Action Objectives (TACO) (35 IAC 742) will be use to develop these Remedial Objectives.

Data gathering activities to be undertaken include:

• Pumping and water level monitoring at the existing Recovery Wells to better assess the hydraulic properties for the shallow sand aquifer;

• Depth-specific sampling in the pond located north of Smiley Road to better estimate tritium concentrations if the pond is to be pumped; and

• Sampling of groundwater for general chemistry and other parameters which might be required for design purposes or for regulatory requirements.

Exelon has already initiated a feasibility study of various potential remedial actions.

One option that can be implemented quickly easily is pumping the surface water from Exelon Pond, piping the water to the south, and discharging the water (untreated) into the blowdown line at VB-2. A similar approach is being considered for the smaller tritium plume near the perimeter ditch and north of VB-1. Here, the surface water in the perimeter ditch or a recovery well would also be pumped and piped directly to the blowdown line at VB-1. 15 This remedial action is meant to be an interim or time critical remedy that will then become part of a long term remedial action plan. In other words, this remedy can be implemented soon, but other remedial components such as additional groundwater pumping, discharge to the new blowdown line, or monitored natural attenuation will take longer.

These interim remedies (either the pond-to-blowdown line or pumping the plume near the perimeter ditch-to-blowdown line) have been selected because they will achieve these goals:

• Design and construction that can be completed quickly;

• Regulatory review is currently proceeding;

• These remedies prevent further migration of the groundwater with tritium above the 20,000 pCi/L standard past the pond or into the perimeter ditch; 15 At this time Exelon is considering either upgrading the existing blowdown line and its vacuum breaker valves or perhaps installing a new blowdown line.

016841 (12) 49 CONESTOGA-ROVERS & ASSOCIATES

• A system which prevents the further off-Site migration of residual tritium greater than 200 pCi/L;

• This system will slow, if not stop, the migration of tritium above the background standards to private property north of the Exelon Pond; and

• This system will reduce the mass of tritium in the groundwater.

At the time of this report Exelon has been in discussion with the IEPA, the Office of the Attorney General, and the Will County State's Attorney regarding this interim remedial action.

016841 (12) 50 CONESTOGA-ROVERS & ASSOCIATES

10.0 REFERENCES

CITED Bouwer, H. and R.C. Rice, 1976. A slug test method for determining hydraulic conductivity of unconfined aquifers with completely or partially penetrating wells, Water Resources Research, vol. 12, no. 3, pp. 423-428.

Illinois Administrative Code Title 35 Part 742, Tiered Approach to Corrective Action Objectives, Illinois Pollution Control Board, effective February 5, 2002.

Sargent and Lundy, 1988. Updated Final Safety Analysis Report (UFSAR), December.

Schicht, Richard J., J. Rodger Adams, and John B. Stall, 1976. Water Resources Availability, Quality, and Cost in Northeastern Illinois, Illinois State Water Survey Report of Investigation 83.

Visocky, Adrian P., Marvin G. Sherrill, and Keros Cartwright, 1985. Geology, Hydrogeology, and Water Quality of the Cambrian and Ordovician Systems in Northern Illinois, Illinois State Geological Survey, Illinois State Water Survey, Cooperative Groundwater Report 10.

Visocky, Adrian P., 1997. Water-Level Trends and Pumpage in the Deep Bedrock Aquifers in the Chicago Region, 1991-1995, Illinois State Water Survey Circular 182.

016841 (12) 51 CONESTOGA-ROVERS & ASSOCIATES

CHANNAHON R

RIVE IS NO I LLI 0 4000 8000ft MORRIS LEGEND VB-1 VACUUM BREAKER LOCATION AND IDENTIFIER BLOW DOWN LINE WILMINGTON COAL CITY KAK 9

12 3 KAN TE 5 U TE O

R OU R EE R IVER BRAIDWOOD VB5 VB6 VB8 VB9 VB10 VB11 VB4 VB3 VB7 EXELON NUCLEAR STATION VB1 VB2 AREA OF INVESTIGATION GODLEY COOLING LAKE BRACEVILLE figure 1.1 SITE LOCATION MAP EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA010 MAR 21/2006

0 200 600ft POND EXELON POND POND VB-3 EXELON NUCLEAR STATION VB-2 VB-1 LEGEND EXISTING FENCE LINE BLOWDOWN LINE figure 2.1 PLANT PROPERTY LINE VB-3 VACUUM BREAKER LOCATION GENERAL SITE BOUNDARIES AND FEATURES EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA011 MAR 21/2006

SOURCE: EXELON NUCLEAR OUTDOOR PIPING ARRANGEMENT, M-900 SHEET NUMBER 6 & 3.

NOT TO SCALE figure 3.1 SCHEMATICS OF THE BLOWDOWN LINE AND VACUUM BREAKERS EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA021 MAR 21/2006

G-2 G-3 G-1 G-2D PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 S-2 S-2D S-3 S-1 PW-8 S-1D F-8D S-7 C-1D S-7D C-1 F-3D S-5 S-6 S-4 PW-7 S-4D C-2D C-2 POND F-7D P-14 MW-110 P-12 P-2D P-3 P-14D F-5D P-2 F-6D P-11 PW-6 PW-15 F-4D BL-19 PW-5 PW-14 P-1 F-2D PW-4 P-10 F-1 EXELON POND F-1D POND BL-18 P-9 P-7 P-13D P-4D BL-17D PW-2 P-8 P-6 P-5D P-4 P-5 BL-17 VB-3-6 RW-1 MW-112 VB2-9D VB-2-6 RW-4 RW-3 RW-2 VB-3-5 MW-111 MW-112D VB-3-9D VB-3-4 BL-16D VB-3-7D MW-111D VB-2-6D VB-2-5 VB-2-3 MW-113D VB-3-4D VB-3-7 MW-109 PW-1 PW-3 VB2-9 VB-2-5D MW-113 BL-16 VB-2-4 VB-3-3 VB-3-8 VB-2-8 VB-2-7 MW-103 VB-3-1 VB-3-10D BL-15D VB-3-2 BL-15 VB1-6D VB-2-7D VB-3-10 VB-2-2D MW-105D VB-3 VB-1-6 MW-104 VB-2-2 BL-12D MW-105 BL-14D VB-1-9 VB1-9D VB-2-1 BL-14 BL-12 BL-13 BL-13D VB-1-7 VB-1-7D BL-20D VB-1-8 MW-102 BL-11D VB-1-8D VB-2 BL-11 BL-10 VB-1-3 BL-09 EXELON NUCLEAR STATION VB-1-5 VB1-3D VB1-5D D-3 D-4 BL-10D BL-08 BL-09D VB-1-4 VB1-4D D-2 D-3D D-2D BL-07 MW-101 VB1-2D D-5 VB-1-2 BL-06 MW-107 D-1D BL-05 VB-1-1 BL-01 D-1 BL-04 MW-106 VB-1 VB-1-1D BL-02 BL-03 MW-108 MW-106D LEGEND EXISTING FENCE LINE MW-105 SHALLOW MONITORING WELL LOCATION BLOWDOWN LINE MW-113D DEEP MONITORING WELL LOCATION PLANT PROPERTY LINE PW-5 PRIVATE WELL LOCATION figure 4.1 BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION P-11 SHALLOW TEMPORARY WELL LOCATION BL-17D DEEP BLOWDOWN LINE SAMPLING LOCATION P-4D DEEP TEMPORARY WELL LOCATION GROUNDWATER MONITORING LOCATIONS VB-3 VACUUM BREAKER LOCATION RW-3 SHALLOW RECOVERY WELL LOCATION EXELON GENERATION BRAIDWOOD STATION VB-3-7 VACUUM BREAKER SAMPLING LOCATION RW-2 DEEP RECOVERY WELL LOCATION 16841-11(012)GN-WA013 MAR 21/2006

0 200 600ft SW-3 POND SW-4 SG-C DS-3 ALPHA GATE EXELON POND SG-A POND PW-6P SW-2 SG-B SW-1 SG-1 DS-2 DS-6 EXELON NUCLEAR STATION SG-2 DS-1b DS-1 DS-10 DS-1a DS-9 SG-3 DS-11 DS-8 LEGEND EXISTING FENCE LINE BLOWDOWN LINE PLANT PROPERTY LINE figure 4.2 SG-1 DS-6 STAFF GAUGE LOCATION DITCH SAMPLING LOCATION SURFACE WATER MONITORING LOCATIONS SW-2 SURFACE WATER SAMPLING LOCATION EXELON GENERATION BRAIDWOOD STATION PW-6P POND SAMPLING LOCATION 16841-11(012)GN-WA014 MAR 21/2006

SOUTHWEST NORTHEAST 600 600 S&G OVERBURDEN EQUALITY FORMATION AQUIFER 580 580 WEDRON FORMATION 560 560 CARBONDALE FORMATION PENNSYLVANIA AQUITARD 540 540 COAL SHALES 520 520 SPOON FORMATION 500 500 SHALLOW BEDROCK AQUIFER 480 480 SILURIAN DOLOSTONES 460 460 ELEVATION IN FEET (MSL)

UNDIFFERENTIAL SILURIAN DOLOSTONES 440 (NOT PRESENT AT THE SITE) 440 420 420 400 400 380 380 360 360 ORDOVICIAN SHALES 340 340 320 MAQUOKETA SHALE GROUP AQUITARD 320 300 300 280 280 260 260 250 250 ORDOVICIAN SANDSTONES DEEP BEDROCK AQUIFER LIMESTONE/DOLOSTONES GALENA AND PLATTEVILLE GROUPS (DEEP BEDROCK AQUIFER) FROM 250 TO 0 GLENWOOD - ST. PETER FORMATION (DEEP BEDROCK AQUIFER) FROM 0 TO -280 CAMBRIAN IRONTON FORMATION (DEEP BEDROCK AQUIFER) FROM -280 TO -1050 SANDSTONES EAU CLAIRE SCALE: HORIZONTAL 1"=400' VERTICAL 1"=40' figure 5.1 LEGEND WATER BEARING UNIT REGIONAL STRATIGRAPHIC SECTION AQUITARD LAYER EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA015 MAR 21/2006

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 PW-8 PW-7 POND PW-6 PW-15 PW-5 PW-14 PW-4 EXELON POND POND PW-2 PW-1 PW-3 VB-3 EXELON NUCLEAR STATION VB-2 VB-1 LEGEND EXISTING FENCE LINE BLOWDOWN LINE PLANT PROPERTY LINE figure 2.2 VB-3 VACUUM BREAKER LOCATION PRIVATE WELL LOCATION PRIVATE WATER SUPPLY WELL LOCATIONS PW-5 PRIVATE WELL LOCATION SCREENED IN SHALLOW AQUIFER EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA012 MAR 21/2006

0 20000 50000ft 750 700 0 0 55 50 65 60 0 0 45 0

WINNEBAGO BOONE MC HENRY LAKE 400 0

75 0

40 700 0

35 0 0 75 30 25 0

OGLE DEKALB KANE COOK 20 0

15 0

-50 0 DUPAGE 100

-50 750 50 LEE 0 100

-50 50 KENDALL WILL 70 0

50 0 15 0

LASALLE

-50 65 0

600 550 GRUNDY 500 450 200 KANKAKEE 250 300 450 350 40 0

LEGEND 45 COUNTY BOUNDARY 0

450 BEDROCK GROUNDWATER LEVEL CONTOUR (1975)

SOURCE: UFSAR FIGURE 2.4-40 DATED OCTOBER 1975.

figure 5.2 REGIONAL DEEP BEDROCK GROUNDWATER LEVEL CONTOURS EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA016 MAR 21/2006

SOUTHWEST NORTHEAST 620 620 LAKE SCREEN HOUSE EXISTING GROUND SURFACE 600 600 OVERBURDEN BLOWDOWN LINE EQUALITY FORMATION 580 580 AQUIFER WEDRON FORMATION 560 560 CHANNEL SANDSTONE DEPOSITS CARBONDALE 540 FRANCIS CREEK SHALE 540 520 SILTSTONE CONG LOME 520 PENNSYLVANIA SHALES RATE SHALE 500 COAL 500 480 480 SPOON FORMATION 460 460 ELEVATION IN FEET (MSL)

AQUITARD 440 440 420 420 400 400 ORDOVICIAN SHALES 380 380 MAQUOKETA SHALE GROUP 360 360 340 340 320 320 300 300 GALENA AND PLATTEVILLE GROUPS (DEEP BEDROCK AQUIFER) FROM 250 TO 0 ORDOVICIAN GLENWOOD - ST. PETER FORMATION (DEEP BEDROCK AQUIFER) FROM 0 TO -280 DEEP 280 280 BEDROCK CAMBRIAN AQUIFER SCALE: HORIZONTAL 1"=400' VERTICAL 1"=40' LEGEND WATER BEARING UNIT AQUITARD LAYER figure 5.3 SITE SPECIFIC GEOLOGIC CROSS-SECTION (UFSAR)

EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA017 MAR 21/2006

G-2D (566.05)

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 S-2D S-1D (569.22)

(567.94) PW-8 C-1D PW-7 (571.00)

POND S-4D (569.41)

P-2D (572.38)

PW-6 PW-15 PW-5 PW-14 PW-4 EXELON POND F-1D (571.27) POND P-5D P-13D P-4D (569.34) BL-17D (569.11) (569.46) (573.01)

VB-2-6D RW-3 RW-2 RW-1 PW-2 (572.01) (572.24) (572.59) (571.68) VB-3-4D (571.18)

PW-3 RW-4 VB-2-5D MW-113D VB-3-9D VB-3-7D PW-1 VB-2-9D (572.31) (571.76) (571.18) BL-16D (572.24)

(572.14)

(570.26) (573.28)

BL-15D MW-105D VB-1-6D VB-2-7D (573.54) (573.22)

(574.86) VB-3-10D VB-3 (575.51)

VB-2-2D (572.99)

(566.99) BL-14D BL-12D BL-13D (570.96)

(570.10) (573.55)

EXELON NUCLEAR STATION BL-9D (570.65)

VB-2 D-3D (571.91)

D-2D D-1D (571.65)

(572.82) MW-106D VB-1 (572.70)

LEGEND EXISTING FENCE LINE PW-5 PRIVATE WELL LOCATION BLOWDOWN LINE P-4D TEMPORARY WELL LOCATION PLANT PROPERTY LINE RW-2 RECOVERY WELL LOCATION figure 5.4 BL-17D BLOWDOWN LINE SAMPLING LOCATION (590.59) ESTIMATED CLAY ELEVATION (ft AMSL)

VB-3 VACUUM BREAKER LOCATION BOTTOM OF SAND/TOP OF CLAY CONTOUR ESTIMATED BOTTOM OF SAND/TOP OF CLAY MAP CONTOURS VB-3-7D VACUUM BREAKER SAMPLING LOCATION EXELON GENERATION BRAIDWOOD STATION MW-113D MONITORING WELL LOCATION 16841-11(012)GN-WA020 MAR 21/2006

P-9 BL-17D BL-17 0 100 200ft P-8 (0.01)

P-6 P-5 P-5D P-4 P-4D P-13D P-7 PW-2 VB-2-6 RW-1 VB-3-5 VB-2-9D RW-2 VB-3-9D VB-3-6 VB-2-3 RW-3 VB-2-6D RW-4 VB-2-5 VB-3-4 BL-16D PW-3 VB2-9 VB-2-5D MW-113D VB-3-4D BL-16 VB-3-7D MW-113 (0.00) VB-3-7 PW-1 (0.00)

VB-3-3 VB-2-4 VB-3-8 MW-103 VB-2-7 VB-3-1 VB-3-10D BL-15D VB-2-7D BL-15 (0.03)

VB-2-8 VB-3-10 VB-3-2 MW-105D VB-3 MW-104 VB-2-2D MW-105 VB-2-2 (-0.37) BL-14D BL-14 BL-12D (-0.29)

VB-2-1 BL-12 BL-13D

(-0.01) BL-13 (0.01)

BL-20D MW-102 BL-11D BL-11 BL-10 (0.02)

BL-10D VB-2 (0.00)

BL-09 BL-09D BL-08 (-0.01)

BL-07 BL-06 MW-101 MW-106 MW-106D LEGEND MW-105 SHALLOW MONITORING WELL LOCATION EXISTING FENCE LINE MW-113D DEEP MONITORING WELL LOCATION BLOWDOWN LINE PW-5 PRIVATE WELL LOCATION PLANT PROPERTY LINE P-11 SHALLOW TEMPORARY WELL LOCATION figure 5.5 BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION P-4D DEEP TEMPORARY WELL LOCATION BL-09D DEEP BLOWDOWN LINE SAMPLING LOCATION RW-3 SHALLOW RECOVERY WELL LOCATION VERTICAL GROUNDWATER GRADIENTS ALONG BLOWDOWN LINE VB-3 VACUUM BREAKER LOCATION RW-2 DEEP RECOVERY WELL LOCATION EXELON GENERATION BRAIDWOOD STATION VB-3-7 VACUUM BREAKER SAMPLING LOCATION (0.01) POSITIVE VERTICAL GRADIENT = UPWARD

(-0.01) NEGATIVE OR ZERO VERTICAL GRADIENT = DOWNWARD 16841-11(012)GN-WA028 MAR 21/2006

G-1 G-2 G-3 (586.02) (586.08)

PW-11 0 200 600ft PW-13 PW-12 PW-10 S-2 PW-9 (588.62)

S-3 S-1 PW-8 (588.59)

(588.54)

S-7 (589.75) PW-7 C-1 POND S-6 S-4 S-5 (589.00)

(589.26) (589.38)

(589.59)

C-2 MW-110 P-2 P-14 (587.81) SG-C P-12 (590.46) P-3 (589.64) V (590.35)

P-11 PW-6 PW-15 (590.03) PW-5 P-1 BL-19 PW-14 (590.57) (590.62)

PW-4 P-10 (590.35)

F-1 EXELON POND SG-A (589.06) POND BL-18 (591.07)

P-9 SG-B (590.75) BL-17 P-7 P-5 P-4 (590.61) (590.93) (591.25)

(590.72)

P-8 P-6 MW-113 (590.65) VB-3-5 PW-2 RW-4 RW-3 (590.80) VB-3-6 RW-1 MW-112 (591.30) VB-3-7 MW-111 (590.90)

(590.85) PW-1 PW-3 VB-2-6 VB-2-5 VB-2-3 VB-3-3 VB-3-4 (591.58)

MW-109 (590.65) VB-2-9 (590.52) (590.94) BL-16 (591.24) (591.04)

(590.82) (590.99)VB-2-4 (591.25) VB-3-8 VB-2-8 (590.87) MW-103 VB-3-1 BL-15 (591.69)

(591.09) (591.24)

VB-2-7 (591.41)

VB-1-9 VB-1-6 VB-3-10 VB-3-2 VB-3 (591.23) VB-2-2 (591.40) (591.53)

(591.49) MW-104 MW-105 (591.56)

VB-2-1 (594.69)

(590.21)

VB-1-7 (591.14) BL-11 BL-13 BL-14 (591.47) (591.24) BL-12 (591.43) (591.61)

VB-1-8 MW-102 VB-1-5 (591.61) (591.92) (591.55)

EXELON NUCLEAR STATION VB-1-3 (591.64) D-4 BL-08 BL-09 BL-10 VB-2 (591.89) D-3 (591.46) (591.16) (591.48) (591.34)

VB-1-2 (591.63) D-2 (591.61) BL-07 MW-107 (592.26) VB-1-4 D-5 MW-101 (592.82) (591.19) D-1 (591.70) BL-05 BL-06 BL-01 (591.42)

(591.79) (591.21) (591.20)

(592.49) MW-108 BL-04 VB-1 VB-1-1 BL-02 BL-03 (592.63) (592.25) (591.59) (591.41)

MW-106 (596.25)

LEGEND EXISTING FENCE LINE MW-105 MONITORING WELL LOCATION BLOWDOWN LINE PW-5 PRIVATE WELL LOCATION PLANT PROPERTY LINE P-11 TEMPORARY WELL LOCATION figure 5.6 VB-3 VACUUM BREAKER LOCATION RW-3 RECOVERY WELL LOCATION BL-19 BLOWDOWN LINE SAMPLING LOCATION (590.80) GROUNDWATER ELEVATION (ft AMSL) GROUNDWATER LEVEL CONTOURS - JANUARY 2006 VB-3-7 SG-B VACUUM BREAKER SAMPLING LOCATION STAFF GAUGE LOCATION GROUNDWATER ELEVATION CONTOUR (ft AMSL)

GROUNDWATER FLOW DIRECTION SHALLOW GROUNDWATER ZONE NOTE:

EXELON GENERATION BRAIDWOOD STATION MONITORING WELL DATA TAKEN JANUARY 3, 2006 TO JANUARY 5, 2006.

16841-11(012)GN-WA018 MAR 21/2006

G-2D (587.00)

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 S-2D S-1D (588.62)

F-8D (589.05) PW-8 (588.72)

S-7D C-1D (589.73) (589.08)

F-3D POND (588.69) S-4D PW-7 F-7D C-2D (587.89)

F-6D P-14D F-5D P-2D (590.61)

(588.02) (590.47)

(589.31)

SG-C F-4D PW-6 PW-15 PW-5 PW-14 (588.72)

PW-4 F-2D (590.00)

F-1D EXELON POND SG-A (589.09) POND SG-B P-5D BL-17D P-13D P-4D (590.46) (590.60) (590.74) (591.31)

VB-2-9D PW-2 (590.24) RW-4 RW-3 RW-2 RW-1 VB-3-4D MW-112D (591.25)

PW-3 VB-2-6D VB-2-5D MW-113D VB-3-9D BL-16D VB-3-7D MW-111D (590.96) PW-1 (590.98) (591.59)

(590.66) (590.17) (590.77) (591.25)

(590.70)

BL-15D VB-3-10D (591.58)

VB-1-6D VB-2-7D (591.37) MW-105D VB-1-9D (591.02) VB-2-2D (591.72) VB-3 (590.70) BL-12D (591.12) (591.47) BL-14D BL-20D VB-1-8D BL-13D (589.20)

VB-1-7D BL-10D (591.29)

(591.97) (591.35) (591.65)

VB-1-5D (591.60) BL-09D BL-11D EXELON NUCLEAR STATION VB-1-3D (592.00) (591.28) VB-2 (591.53)

(592.30) D-3D VB-1-4D (591.62)

(593.11)

VB-1-2D D-2D (592.49) D-1D (591.71)

(591.77)

VB-1 VB-1-1D MW-106D (592.29)

LEGEND EXISTING FENCE LINE PW-5 PRIVATE WELL LOCATION BLOWDOWN LINE P-4D TEMPORARY WELL LOCATION PLANT PROPERTY LINE RW-2 RECOVERY WELL LOCATION BL-17D BLOWDOWN LINE SAMPLING LOCATION (590.59) GROUNDWATER ELEVATION (ft AMSL) figure 5.7 VB-3 VACUUM BREAKER LOCATION GROUNDWATER ELEVATION CONTOUR (ft AMSL)

VB-3-7D VACUUM BREAKER SAMPLING LOCATION GROUNDWATER FLOW DIRECTION GROUNDWATER LEVEL CONTOURS - JANUARY 2006 MW-113D SG-B MONITORING WELL LOCATION STAFF GAUGE LOCATION DEEP GROUNDWATER ZONE NOTE:

EXELON GENERATION BRAIDWOOD STATION MONITORING WELL DATA TAKEN JANUARY 3, 2006 TO JANUARY 24, 2006.

16841-11(012)GN-WA019 MAR 21/2006

0 200 600ft G-1 G-2 G-3 (133) (87) (81)

PW-11 PW-13 SW-3 (96) PW-12 PW-10 PW-9 A-1 S-2 (33) S-1 (62) S-3 (83) (57)

PW-8 POND C-1

(-80)

S-5 S-4 PW-7 S-6 (1874) (1086)

(411)

C-2 SW-4

(-48)

(83)

MW-110 P-12 P-2 P-3

(-104) (1622) (2045) (2537)

DS-3 P-11 PW-15 (1476) PW-6 BL-19 PW-5 PW-14 (37)

PW-4 P-10 PSG-1 EXELON POND P-1 (1723)

(2484)

F-1 POND PW-6P

(-44)

(142) 0 20 BL-18 (108)

P-9 SW-2 (111) SW-1 (2441)

(2464) P-5 P-4 PSG-2 (6166) BL-17 P-8 (9588)

(2212) P-7 P-6 (-44)

(1210) RW-4 (110) MW-113 VB-3-6 RW-1 VB-3-5 MW-112 PW-2 (53572)

RW-3 (4008) (95)

SG-1 MW-111 (-127) VB-3-3 VB-3-7 PW-3 VB-2-6 VB-2-5 VB-2-3 RW-2 (43894)VB-3-4 200 MW-109

(-78)

(1412) (3834) (3940) (29286) BL-16

(-126)

PW-1 5 00 VB-3-2 (3364) VB-3-8 (305) (32830) BL-15 (171)

VB-2-8

(-103) VB-2-7 VB-2-4 MW-103 0 VB-3-10 (146)

(3664) (2497) VB-3-1 (12076)

VB-1-6 VB-3 VB-1-9 (95)

(-60) MW-104 5000 (5959) MW-105 BL-14 (142) (169)

(107) VB-2-2 VB-2-1 (-37)

VB-1-7 (5232) BL-13 (140) (2) MW-102 VB-1-8 BL-12 (-16)

DS-2 BL-09 (58) BL-11 (-39)

VB-1-3 (57) DS-6 20 (4809)

(206) VB-1-5 BL-08 0 VB-2 (13)

(130) D-4 BL-10 20 VB-1-4 BL-07 (-104)

(91) (90) 0 (384) D-3 BL-06 (39)

MW-107 (-168) D-5 MW-101 VB-1-2 D-2 (114)

(269) BL-05 (162)

(337) BL-02 D-1 (-165) (73)

VB-1 (-13) BL-03 BL-04 (102)

(156) SG-2 BL-01 (0) (40) MW-106 VB-1-1 (425) (70) MW-108 DS-1 DS-10 (-35)

(91) DS-1b DS-1a DS-9 DS-11 SG-3 DS-8 DS-7 LEGEND:

EXISTING FENCE LINE EXISTING PERIMETER DITCH LIMITS TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIES/LITER)

BLOWDOWN LINE TRITIUM RESULTS 100,000 TO 200,000 PLANT PROPERTY LINE TRITIUM RESULTS 60,000 TO 100,000 BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION TRITIUM RESULTS 40,000 TO 60,000 VB-3 VACUUM BREAKER LOCATION TRITIUM RESULTS 20,000 TO 40,000 VB-3-7 VACUUM BREAKER SAMPLING LOCATION TRITIUM RESULTS 10,000 TO 20,000 MW-105 SHALLOW MONITORING WELL LOCATION TRITIUM RESULTS 5,000 TO 10,000 PW-5 PRIVATE WELL LOCATION TRITIUM RESULTS 200 TO 5,000 P-11 SHALLOW TEMPORARY WELL LOCATION TRITIUM RESULTS 0 TO 200 PSG-1 STAFF GAUGE LOCATION NOTE:

BACKGROUND TRITIUM CONCENTRATION: 200 pCi/L DS-6 DITCH SAMPLING LOCATION DRINKING WATER STANDARD FOR TRITIUM: 20,000 pCi/L SW-2 TRITIUM DATA FOR SAMPLES COLLECTED THROUGH SURFACE WATER SAMPLING LOCATION JANUARY 30, 2006. CONTOURS WERE GENERATED RW-3 SHALLOW RECOVERY WELL LOCATION USING LOG VALUES. figure 6.1 PW-6P POND SAMPLING LOCATION ESTIMATED TRITIUM RESULTS (2,484) TRITIUM RESULT IN GROUNDWATER SHALLOW GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION 200 TRITIUM CONTOUR 16841-11(012)GN-WA022 MAR 21/2006

0 200 600ft G-2D (67)

PW-11 PW-13 PW-12 PW-10 S-2D A-1D PW-9

(-2)

(60) S-1D F-8D (1287) PW-8 (872)

POND C-1D S-7D

(-140)

F-3D (1546)

PW-7 (1689) S-4D F-7D (2111)

C-2D (575)

P-14D (147)

F-6D F-5D P-2D (2388)

(689) (1512) (2384)

F-4D EXELON POND PW-15 (-22) PW-5 PW-6 PW-14 PW-4 F-2D (546)

F-1D

(-56) POND 20 0

20000 P-4D P-13D 5000 (217122) (38965) BL-17D P-5D (-126)

VB-2-6D RW-1 VB-3-4D PW-2 (44) RW-4 (2165)

MW-111D MW-112D RW-3 (790)

PW-3 RW-2 VB-3-9D VB-3-7D

(-66) (-111) PW-1 VB-2-5D MW-113D VB-2-9D (102) (19605) BL-16D (-205)

(4772)

(-65) (-91)

VB-2-7D BL-15D

(-53) VB-3-10D (-49) 20 VB-1-6D (108736) MW-105D VB-3 0 (41) VB-2-2D (-120)

(4037) BL-12D BL-14D VB-1-9D 50 (-35) (-91)

(3370) VB-1-7D BL-13D 00 BL-10D

(-116) 00 (7535) (9)

VB-1-3D VB-1-5D VB-1-8D BL-09D 50 BL-11D BL-20D (-27)

(19431) (22928) (10877) (20383) VB-2 (-117)

D-3D (5110)

VB-1-2D VB-1-4D D-2D (238) (7424)

VB-1 (-36)

D-1D VB-1-1D (-141) MW-106D

(-132) (-25)

LEGEND EXISTING FENCE LINE TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIES/LITER)

EXISTING PERIMETER DITCH LIMITS TRITIUM RESULTS 100,000 TO 200,000 BLOWDOWN LINE TRITIUM RESULTS 60,000 TO 100,000 PLANT PROPERTY LINE TRITIUM RESULTS 40,000 TO 60,000 BL-17D DEEP BLOWDOWN LINE SAMPLING LOCATION TRITIUM RESULTS 20,000 TO 40,000 VB-3 VACUUM BREAKER LOCATION TRITIUM RESULTS 10,000 TO 20,000 VB-3-7D DEEP VACUUM BREAKER SAMPLING LOCATION TRITIUM RESULTS 5,000 TO 10,000 MW-113D DEEP MONITORING WELL LOCATION TRITIUM RESULTS 200 TO 5,000 PW-5 PRIVATE WELL LOCATION TRITIUM RESULTS 0 TO 200 P-4D DEEP TEMPORARY WELL LOCATION NOTE:

PW-6P POND SAMPLING LOCATION BACKGROUND TRITIUM CONCENTRATION: 200 PCI/L DRINKING WATER STANDARD FOR TRITIUM: 20,000 PCI/L RW-2 DEEP RECOVERY WELL LOCATION TRITIUM DATA FOR SAMPLES COLLECTED THROUGH JANUARY 30, 2006. CONTOURS WERE GENERATED (2,484) TRITIUM RESULT IN GROUNDWATER USING LOG VALUES. figure 6.2 200 TRITIUM CONTOUR ESTIMATED TRITIUM RESULTS DEEP GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA023 MAR 21/2006

G-2 G-3 G-1 PW-11 0 200 600ft PW-13 SW-3 PW-12 PW-10 PW-9 S-2 S-1 S-3 PW-8 POND S-7 C-1 S-5 S-6 S-4 PW-7 V

C-2 SW-4 VB-4-1 MW-110 P-12 P-3 P-14 P-2 P-11 PW-6 PW-15 PW-5 PW-14 P-1 BL-19 PW-4 P-10 F-1 EXELON POND POND BL-18 P-9 SW-1 SW-2 BL-17 PW-2 P-8 P-6 P-4 P-7 P-5 VB-3-6 RW-1 VB-2-6 RW-4 RW-3 VB-3-5 MW-111 MW-113 VB-3-4 VB-3-7 MW-112 VB-2-5 VB-2-3 MW-109 PW-3 VB2-9 BL-16 PW-1 VB-3-3 VB-2-4 VB-2-8 MW-103 VB-3-1 VB-3-2 BL-15 VB-3-8 VB-2-7 VB-3-10 VB-2-2 MW-105 VB-3 VB-1-6 MW-104 BL-14 VB-1-9 BL-12 BL-13 VB-2-1 VB-1-7 BL-11 VB-1-8 MW-102 BL-10 VB-2 BL-09 EXELON NUCLEAR STATION VB-1-5 D-3 BL-08 VB-1-3 D-4 BL-07 VB-1-4 D-2 BL-06 MW-101 D-5 VB-1-2 D-1 BL-05 MW-107 BL-02 VB-1-1 BL-01 MW-108 BL-03 BL-04 MW-106 VB-1 LEGEND EXISTING FENCE LINE P-11 SHALLOW TEMPORARY WELL LOCATION BLOWDOWN LINE RW-3 SHALLOW RECOVERY WELL LOCATION figure 6.3 PLANT PROPERTY LINE SW-2 SURFACE WATER SAMPLING LOCATION BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION SAMPLE LOCATION MAXIMUM DETECTIONS OF TRITIUM IN THE VB-3 VACUUM BREAKER LOCATION BL-05 11/18/05 SAMPLE DATE SHALLOW GROUNDWATER ZONE THROUGH JANUARY 2006 VB-3-7 VACUUM BREAKER SAMPLING LOCATION 3H-Tritium 102 RESULT (pCi/L) EXELON GENERATION BRAIDWOOD STATION MW-105 SHALLOW MONITORING WELL LOCATION PARAMETER PW-5 PRIVATE WELL LOCATION 16841-11(012)GN-WA025 MAR 21/2006

G-2D PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 S-2D PW-8 S-1D F-8D S-7D C-1D F-3D PW-7 S-4D F-7D C-2D POND P-2D P-14D F-5D F-6D PW-6 PW-15 F-4D PW-5 PW-14 F-2D PW-4 EXELON POND F-1D POND P-13D P-4D BL-17D PW-2 P-5D VB2-9D VB-2-5D RW-2 MW-112D VB-2-6D VB-3-9D BL-16D VB-3-7D MW-111D MW-113D VB-3-4D PW-1 PW-3 VB-3-10D BL-15D VB1-6D VB-2-7D VB-2-2D MW-105D VB-3 BL-12D BL-14D VB1-9D BL-13D BL-20D VB-1-8D VB-1-7D BL-11D BL-10D VB-2 BL-09D EXELON NUCLEAR STATION VB1-5D VB1-3D D-3D VB1-4D VB1-2D D-2D D-1D VB-1 VB-1-1D MW-106D LEGEND EXISTING FENCE LINE P-4D DEEP TEMPORARY WELL LOCATION BLOWDOWN LINE RW-2 DEEP RECOVERY WELL LOCATION figure 6.4 PLANT PROPERTY LINE BL-17D DEEP BLOWDOWN LINE SAMPLING LOCATION SAMPLE LOCATION MAXIMUM DETECTIONS OF TRITIUM IN THE SAMPLE DATE VB-3 VACUUM BREAKER LOCATION BL-09D 3H-Tritium 12/23/05 23097 RESULT (pCi/L) DEEP GROUNDWATER ZONE THROUGH JANUARY 2006 VB-3-7D VACUUM BREAKER SAMPLING LOCATION PARAMETER EXELON GENERATION BRAIDWOOD STATION MW-113D DEEP MONITORING WELL LOCATION PW-5 PRIVATE WELL LOCATION 16841-11(012)GN-WA026 MAR 21/2006

A G-2 G-3 G-1 G-2D PW-11 PW-13 PW-12 PW-10 0 200 600ft PW-9 S-2 S-2D S-3 S-1 PW-8 S-1D F-8D POND S-7 C-1D S-7D C-1 F-3D S-5 S-4 S-6 PW-7 S-4D C-2D C-2 F-7D P-14 MW-110 P-12 P-2D P-3 P-14D F-6D F-5D P-2 P-11 PW-6 PW-15 F-4D BL-19 PW-5 PW-14 P-1 F-2D PW-4 P-10 F-1 EXELON POND F-1D POND BL-18 P-9 B'

B PW-2 P-8 P-7 P-6 P-5D P-5 P-13D P-4D P-4 VB-3-6 RW-1 BL-17D BL-17 RW-4 RW-3 MW-112 VB2-9D VB-2-6 RW-2 VB-3-5 MW-111 MW-112D VB-3-9D VB-3-4 BL-16D VB-3-7D MW-111D VB-2-6D VB-2-5 VB-2-3 MW-113D VB-3-4D VB-3-7 MW-109 PW-1 PW-3 VB2-9 VB-2-5D MW-113 BL-16 VB-2-4 VB-3-3 VB-3-8 VB-2-8 VB-2-7 MW-103 VB-3-1 VB-3-10D BL-15D VB-3-2 BL-15 VB1-6D VB-2-7D VB-3-10 VB-2-2D MW-105D VB-3 VB-1-6 MW-104 VB-2-2 BL-12D MW-105 BL-14D VB-1-9 VB1-9D VB-2-1 BL-14 BL-12 BL-13 BL-13D VB-1-7 VB-1-7D BL-20D VB-1-8 MW-102 BL-11D VB-1-8D VB-2 BL-11 BL-10 VB-1-3 BL-09 EXELON NUCLEAR STATION VB-1-5 VB1-3D VB1-5D D-3 D-4 BL-10D BL-08 BL-09D VB-1-4 VB1-4D D-2 D-3D D-2D BL-07 MW-101 VB1-2D D-5 VB-1-2 BL-06 MW-107 D-1D BL-05 VB-1-1 BL-01 D-1 BL-04 MW-106 VB-1 VB-1-1D BL-02 BL-03 MW-108 MW-106D A'

LEGEND EXISTING FENCE LINE MW-105 SHALLOW MONITORING WELL LOCATION BLOWDOWN LINE MW-113D DEEP MONITORING WELL LOCATION figure 6.5 PLANT PROPERTY LINE PW-5 PRIVATE WELL LOCATION BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION P-11 SHALLOW TEMPORARY WELL LOCATION HYDROGEOLOGIC PROFILE LOCATIONS BL-17D DEEP BLOWDOWN LINE SAMPLING LOCATION P-4D DEEP TEMPORARY WELL LOCATION EXELON GENERATION BRAIDWOOD STATION VB-3 VACUUM BREAKER LOCATION RW-3 SHALLOW RECOVERY WELL LOCATION VB-3-7 VACUUM BREAKER SAMPLING LOCATION RW-2 DEEP RECOVERY WELL LOCATION 16841-11(012)GN-WA006 MAR 21/2006

P-13D (OFFSET 77'E)

VB-3-1 (OFFSET 20'E) BL-12(OFFSET 40'W) 8" WATER MAKE UP LINE INTERSECTION A'

S-1 (OFFSET 138'W)

A MW-106 P-2 (OFFSET 59'E) VB-3-10 (OFFSET 88'E)

PW-9 (OFFSET 203'W)

BL-12D (OFFSET 40'W)

VACUUM PW-11 (OFFSET 92'E)

MW-106D 605 605 RW-2 (OFFSET 33'E) OF B-B' BREAKER #3 VB-3-10D (OFFSET 88'E)

S-1D (OFFSET 137'W) P-2D (OFFSET 59'E) 600 X 600 G-1 596.25 594.80 595 1/5/06 595 591.40 591.55 590.86 1/3/06 590.47 1/5/06 1/3/06 590.46 592.29 1/4/06 1/4/06 591.47 590.32 590.6 590.60 591.24 590.37 1/4/06 590 1/3/06 590 1/3/06 589.05 SW-2 1/25/06 1000 1/5/06 00 1/3/06 588.54 1/5/06 1/26/2006 2441 0 50 01/25/06 VB-3-10 VB-3-1 12076 MW-106 5959 01/03/06 -35 585 11/15/05 01/04/06 585 0 200 P-2 BL-12 S-1 2045 00 -39 83 12/06/05 01/03/06 20 01/03/06 580 580 G-1 133 40000 12/06/05 200 60000 VB-3-10D MW-106D P-2D 5000 575 10 108736 -25 575 2384 00 0

01/03/06 1000 00 01/04/06 0

01/03/06 BL-12D 2000

-35 P-13D 01/03/06 01/25/06 570 S-1D 570 217122 1287 01/26/06 565 565 560 560 SCALE: HORIZONTAL: 1"=400' 555 VERTICAL: 1"=40' 555 LEGEND 550 550 G-1 WELL ID TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIES/LITER)

TRITIUM RESULTS 10,000 TO 200,000 TRITIUM RESULTS 60,000 TO 100,000 590.32 GRONDWATER ELEVATION 1/3/06 TRITIUM RESULTS 40,000 TO 60,000 WELL TRITIUM RESULTS 20,000 TO 40,000 TRITIUM RESULTS 10,000 TO 20,000 figure 6.6 TRITIUM RESULTS 5,000 TO 10,000 SITE SPECIFIC HYDROGEOLOGIC PROFILE WELL SCREEN G-1 TRITIUM CONCENTRATION TRITIUM RESULTS 200 TO 5,000 JANUARY 2006 (A-A')

133 12/06/05 EXELON GENERATION BRAIDWOOD STATION TRITIUM RESULTS 0 TO 200 16841-11(012)GN-WA006 MAR 21/2006

MW-111 (OFFSET 51'S)

VB-2-3 (OFFSET 64'S)

MW-112 (OFFSET 44'S) VB-2-6 (OFFSET 43'S)

RW-3 (OFFSET 47'S)

MW-111D (OFFSET 51'S) 48" WATER MAKE UP LINE VB-3-6 (OFFSET 40'S)

MW-113 (OFFSET 78'S)

VB-2-6D (OFFSET 43'S)

VB-3-9D (OFFSET 30'S)

PW-1 (OFFSET 102'S) VB-3-5 (OFFSET 52'S)

B B' PW-2 (OFFSET 14'S)

MW-112D (OFFSET 44'S)

PW-3 (OFFSET 71'S)

MW-113D (OFFSET 78'S)

X RW-4 (OFFSET 49'S)

INTERSECTION OF A-A' 605 605 VB-2-5 (OFFSET 52'S)

VB-2-5D (OFFSET 52'S) P-13D (OFFSET 59'N) RW-1 (OFFSET 46'S) 600 600 595 MW-111 595

-78 593.50 590.80 590.94 590.80 590.91 590.90 1/4/06 1/3/06 1/5/06 1/5/06 1/3/06 1/3/06 1/5/06 591.30 590.85 590.66 1/5/06 590 590.65 590.70 1/3/06 590.86 1/3/06 590.52 590.82 590.77 590.98 591.13 590 1/4/06 1/9/06 MW-112 1/9/06 1/3/06 590.17 1/5/06 1/3/06 1/4/06 1/5/06

-127 1/3/06 1/4/06 VB-2-3 MW-113 585 3940 4008 4000 VB-3-5 585 0

11/15/05 1/3/06 VB-3-6 VB-2-6 95 VB-2-5 53572 1412 11/22/05 3834 11/22/05 1/3/06 1/3/06 580 20 500 580 MW-111D

-66 0 100000 1/9/06 2000 0 575 MW-112D VB-2-6D VB-2-5D MW-113D 575

-111 4772 VB-3-9D 44 102 1/9/06 1/3/06 19605 1/3/06 1/3/06 1/4/06 P-13D 570 217122 570 1/25/06 565 565 560 SCALE: HORIZONTAL: 1"=400' 560 VERTICAL: 1"=40' 555 LEGEND 555 G-1 WELL ID TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIES/LITER) 550 TRITIUM RESULTS 10,000 TO 200,000 550 TRITIUM RESULTS 60,000 TO 100,000 590.32 GRONDWATER ELEVATION 1/3/06 TRITIUM RESULTS 40,000 TO 60,000 WELL TRITIUM RESULTS 20,000 TO 40,000 TRITIUM RESULTS 10,000 TO 20,000 figure 6.7 TRITIUM RESULTS 5,000 TO 10,000 SITE SPECIFIC HYDROGEOLOGIC PROFILE WELL SCREEN G-1 TRITIUM CONCENTRATION TRITIUM RESULTS 200 TO 5,000 JANUARY 2006 (B-B')

133 12/06/05 EXELON GENERATION BRAIDWOOD STATION TRITIUM RESULTS 0 TO 200 16841-11(012)GN-WA006 MAR 21/2006

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 PW-8 PW-7 POND PW-5 PW-6 PW-15 PW-14 PW-4 EXELON POND POND PW-2 PW-3 PW-1 VB-3 EXELON NUCLEAR STATION VB-2 VB-1 LEGEND EXISTING FENCE LINE BLOWDOWN LINE SAMPLE LOCATION figure 6.8 PLANT PROPERTY LINE PW-1 11/30/05 SAMPLE DATE VB-3 VACUUM BREAKER LOCATION 3H-Tritium -26 RESULT (pCi/L) MAXIMUM DETECTIONS OF TRITIUM THROUGH JANUARY 2006 IN PRIVATE WELLS PW-5 PRIVATE WELL LOCATION PARAMETER EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA024 MAR 21/2006

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 PW-8 PW-7 POND PW-6 PW-15 PW-5 PW-14 PW-4 EXELON POND 20000 POND PW-2 PW-1 PW-3 MODELED SOURCE VB-3 LOCATION EXELON NUCLEAR STATION VB-2 VB-1 LEGEND EXISTING FENCE LINE figure 7.1 BLOWDOWN LINE PLANT PROPERTY LINE GRAPHICAL PRESENTATION OF BIOSCREEN MODELING VB-3 VACUUM BREAKER LOCATION PRIVATE WELL LOCATION RESULTS AND LOCATION OF WATER SUPPLY WELLS PW-5 MAXIMUM EXTENT OF TRITIUM NOTE: PLUME REACHES STEADY EXELON GENERATION BRAIDWOOD STATION PLUME AT DRINKING WATER STATE IN 30 YEARS (2036).

STANDARD (20000 pCi/L) 16841-11(012)GN-WA029 MAR 21/2006

TABLE 4.1 Page 1 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 A-1 594.28 597.00 15.0 10 to 15 584.28 579.28 1 PVC4 2.72 A-1D 594.32 597.34 25.0 20 to 25 574.32 569.32 1 PVC 3.02 B-01 594.58 598.65 15.0 10 to 15 584.58 579.58 1 PVC 4.07 B-01D 594.69 596.53 28.0 23 to 28 571.69 566.69 1 PVC 1.84 BL-01 600.38 605.58 17.0 12 to 17 588.38 583.38 1 PVC 5.20 BL-02 600.16 604.84 14.5 9.5 to 14.5 590.66 585.66 1 PVC 4.68 BL-03 600.60 604.50 23.0 18 to 23 582.60 577.60 1 PVC 3.90 BL-04 599.76 601.91 14.5 10 to 15 589.76 584.76 1 PVC 2.15 BL-05 599.76 602.60 21.0 16 to 21 583.76 578.76 1 PVC 2.84 BL-06 597.74 601.83 15.0 10 to 15 587.74 582.74 1 PVC 4.09 BL-07 597.57 601.08 15.0 10 to 15 587.57 582.57 1 PVC 3.51 BL-08 598.53 602.29 15.0 10 to 15 588.53 583.53 1 PVC 3.76 BL-09 5 599.75 602.75 12.5 7.5 to 12.5 592.25 587.25 1 PVC 3.00 BL-09 599.60 602.49 22.0 16 to 21 583.60 578.60 1 PVC 2.89 BL-09D 599.65 600.36 29.0 24 to 29 575.65 570.65 1 PVC 0.71 BL-10 602.49 605.37 15.0 10 to 15 592.49 587.49 1 PVC 2.88 BL-10D 602.43 605.16 32.0 27 to 32 575.43 570.43 1 PVC 2.73 BL-11 597.47 600.65 15.0 10 to 15 587.47 582.47 1 PVC 3.18 BL-11D 597.34 599.09 28.0 23 to 28 574.34 569.34 1 PVC 1.75 BL-12 598.03 601.60 15.0 10 to 15 588.03 583.03 1 PVC 3.57 BL-12D 598.10 599.87 28.0 23 to 28 575.10 570.10 1 PVC 1.77 BL-13 598.07 601.37 15.0 10 to 15 588.07 583.07 1 PVC 3.30 BL-13D 598.05 600.82 24.5 19.5 to 24.5 578.55 573.55 1 PVC 2.77 BL-14 597.34 601.26 15.0 10 to 15 587.34 582.34 1 PVC 3.92 BL-14D 597.46 599.90 26.5 21.5 to 26.5 575.96 570.96 1 PVC 2.44 BL-15 597.29 600.98 15.0 10 to 15 587.29 582.29 1 PVC 3.69 BL-15D 597.54 598.50 24.0 19 to 24 578.54 573.54 1 PVC 0.96 BL-16 597.12 600.30 15.0 10 to 15 587.12 582.12 1 PVC 3.18 BL-16D 597.28 598.17 24.0 19 to 24 578.28 573.28 1 PVC 0.89 BL-17 597.01 597.62 14.5 9.5 to 14.5 587.51 582.51 1 PVC 0.61 BL-17D 597.01 598.11 25.0 19 to 24 578.01 573.01 1 PVC 1.10 BL-18 596.82 597.59 14.5 9.5 to 14.5 587.32 582.32 1 PVC 0.77 BL-18D 596.66 598.57 27.0 22 to 27 574.66 569.66 1 PVC 1.91 BL-19 594.94 595.55 9.0 4 to 9 590.94 585.94 1 PVC 0.61 BL-19D 595.06 596.93 28.2 23.2 to 28.2 571.86 566.86 1 PVC 1.87 BL-20D 596.89 600.45 29.0 23 to 28 573.89 568.89 1 PVC 3.56 CRA 016841 (12)

TABLE 4.1 Page 2 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 C-1 595.00 595.78 14.0 9 to 14 586.00 581.00 1 PVC 0.78 C-1D 595.00 595.87 25.0 19 to 24 576.00 571.00 1 PVC 0.87 C-2 606.94 610.91 15.5 10.5 to 15.5 596.44 591.44 1 PVC 3.97 C-2D 606.82 609.03 27.5 22.5 to 27.5 584.32 579.32 1 PVC 2.21 D-1 599.64 603.69 15.0 10 to 15 589.64 584.64 1 PVC 4.05 D-1D 599.82 603.77 27.0 22 to 27 577.82 572.82 1 PVC 3.95 D-2 598.78 601.92 12.0 7 to 12 591.78 586.78 1 PVC 3.14 D-2D 598.65 601.47 28.0 22 to 27 576.65 571.65 1 PVC 2.82 D-3 599.00 602.48 12.0 7 to 12 592.00 587.00 1 PVC 3.48 D-3D 598.91 602.22 28.0 22 to 27 576.91 571.91 1 PVC 3.31 D-4 598.48 602.55 15.0 10 to 15 588.48 583.48 1 PVC 4.07 D-5 598.58 602.27 12.0 7 to 12 591.58 586.58 1 PVC 3.69 F-1 595.27 596.25 14.0 9 to 14 586.27 581.27 1 PVC 0.98 F-1D 595.27 596.19 25.0 19 to 24 576.27 571.27 1 PVC 0.92 F-2D 594.05 597.26 25.0 20 to 25 574.05 569.05 1 PVC 3.21 F-3D 594.59 597.36 25.0 20 to 25 574.59 569.59 1 PVC 2.77 F-4D 595.57 599.59 29.5 24.5 to 29.5 571.07 566.07 1 PVC 4.02 F-5D 593.38 595.96 27.0 22 to 27 571.38 566.38 1 PVC 2.58 F-6D 595.05 597.28 27.5 22.5 to 27.5 572.55 567.55 1 PVC 2.23 F-7D 594.38 596.37 28.0 23 to 28 571.38 566.38 1 PVC 1.99 F-8D 594.60 598.42 26.0 21 to 26 573.60 568.60 1 PVC 3.82 G-1 590.70 595.35 14.5 9.5 to 14.5 581.20 576.20 1 PVC 4.65 G-2 590.24 590.82 14.5 9.5 to 14.5 580.74 575.74 1 PVC 0.58 G-2D 590.05 590.65 25.0 19 to 24 571.05 566.05 1 PVC 0.60 G-3 592.34 592.93 14.5 9.5 to 14.5 582.84 577.84 1 PVC 0.59 MW-101 599.49 602.77 10.0 5 to 10 594.49 589.49 2 PVC 3.28 MW-102 602.42 605.70 11.0 6 to 11 596.42 591.42 2 PVC 3.28 MW-103 595.72 598.84 8.0 3 to 8 592.72 587.72 2 PVC 3.12 MW-104 596.60 598.80 8.0 3 to 8 593.60 588.60 2 PVC 2.20 MW-105 597.29 600.74 16.0 5 to 15 592.29 582.29 2 PVC 3.45 MW-105D 597.22 598.20 24.0 19 to 24 578.22 573.22 1 PVC 0.98 MW-106 599.60 602.73 16.0 5 to 15 594.60 584.60 2 PVC 3.13 MW-106D 599.70 601.81 27.0 22 to 27 577.70 572.70 1 PVC 2.11 MW-107 599.85 603.24 16.0 5 to 15 594.85 584.85 2 PVC 3.39 MW-108 599.76 603.10 16.0 5 to 15 594.76 584.76 2 PVC 3.34 MW-109 598.81 601.23 16.0 5 to 15 593.81 583.81 2 PVC 2.42 CRA 016841 (12)

TABLE 4.1 Page 3 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 MW-110 604.01 607.27 20.0 9.5 to 19.5 594.51 584.51 2 PVC 3.26 MW-111 603.29 607.20 16.0 5.5 to 15.5 597.79 587.79 2 PVC 3.91 MW-111D 603.17 605.05 26.5 21.5 to 26.5 581.67 576.67 1 PVC 1.88 MW-112 598.57 602.62 16.0 5.5 to 15.5 593.07 583.07 2 PVC 4.05 MW-112D 598.61 600.85 26.0 21 to 26 577.61 572.61 1 PVC 2.24 MW-113 596.10 599.77 16.0 5.5 to 15.5 590.60 580.60 2 PVC 3.67 MW-113D 596.14 596.90 25.0 19 to 24 577.14 572.14 1 PVC 0.76 P-1 594.90 595.59 14.5 9.5 to 14.5 585.40 580.40 1 PVC 0.69 P-2 595.65 596.27 14.5 9.5 to 14.5 586.15 581.15 1 PVC 0.62 P-2D 595.88 596.55 24.0 18.5 to 23.5 577.38 572.38 1 PVC 0.67 P-3 595.69 596.26 14.5 9.5 to 14.5 586.19 581.19 1 PVC 0.57 P-4 595.69 597.14 14.5 9.5 to 14.5 586.19 581.19 1 PVC 1.45 P-4D 596.46 599.22 27.0 22 to 27 574.46 569.46 1 PVC 2.76 P-5 596.34 597.06 15.0 10 to 15 586.34 581.34 1 PVC 0.72 P-5D 596.34 599.37 27.0 22 to 27 574.34 569.34 1 PVC 3.03 P-6 597.57 597.85 14.5 9.5 to 14.5 588.07 583.07 1 PVC 0.28 P-7 599.77 600.24 14.5 9.5 to 14.5 590.27 585.27 1 PVC 0.47 P-8 595.49 596.24 14.5 9.5 to 14.5 585.99 580.99 1 PVC 0.75 P-9 598.55 599.19 14.5 9.5 to 14.5 589.05 584.05 1 PVC 0.64 P-10 596.08 596.58 14.5 9.5 to 14.5 586.58 581.58 1 PVC 0.50 P-11 595.19 596.23 14.5 9.5 to 14.5 585.69 580.69 1 PVC 1.04 P-12 595.56 596.13 14.5 9.5 to 14.5 586.06 581.06 1 PVC 0.57 P-13D 596.11 598.76 27.0 22 to 27 574.11 569.11 1 PVC 2.65 P-14 596.52 599.14 15.5 10.5 to 15.5 586.02 581.02 1 PVC 2.62 P-14D 596.65 598.50 28.0 23 to 28 573.65 568.65 1 PVC 1.85 PS-1 543.95 546.13 12.0 6 to 11 537.95 532.95 1 PVC 2.18 PS-2 542.12 546.76 11.0 5 to 10 537.12 532.12 1 PVC 4.64 PS-3 547.16 550.09 12.0 6 to 11 541.16 536.16 1 PVC 2.93 PS-4 547.78 548.90 13.75 8.75 to 13.75 539.03 534.03 1 PVC 1.12 PS-5 548.41 550.24 13.0 8 to 13 540.41 535.41 1 PVC 1.83 PS-6 543.94 547.40 12.0 7 to 12 536.94 531.94 1 PVC 3.46 RW-1 596.68 599.36 28.0 5 to 25 591.68 571.68 4 PVC 2.68 RW-2 596.59 599.30 25.0 4 to 24 592.59 572.59 4 PVC 2.71 RW-3 596.24 599.19 24.0 4 to 24 592.24 572.24 4 PVC 2.95 RW-4 596.31 598.77 24.0 4 to 24 592.31 572.31 4 PVC 2.46 S-1 594.99 595.60 14.5 9.5 to 14.5 585.49 580.49 1 PVC 0.61 CRA 016841 (12)

TABLE 4.1 Page 4 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 S-1D 594.94 596.92 28.0 22 to 27 572.94 567.94 1 PVC 1.98 S-2 592.72 593.32 14.5 9.5 to 14.5 583.22 578.22 1 PVC 0.60 S-2D 592.72 593.98 24.0 18.5 to 23.5 574.22 569.22 1 PVC 1.26 S-3 592.65 593.37 14.5 9.5 to 14.5 583.15 578.15 1 PVC 0.72 S-4 594.23 594.63 14.5 9.5 to 14.5 584.73 579.73 1 PVC 0.40 S-4D 593.91 596.67 25.5 19.5 to 24.5 574.41 569.41 1 PVC 2.76 S-5 592.76 593.44 14.5 9.5 to 14.5 583.26 578.26 1 PVC 0.68 S-6 594.99 595.57 14.5 9.5 to 14.5 585.49 580.49 1 PVC 0.58 S-7 593.54 594.73 13.6 8.6 to 13.6 584.94 579.94 1 PVC 1.19 S-7D 593.50 596.53 27.5 22.5 to 27.5 571.00 566.00 1 PVC 3.03 VB-1-1 602.14 605.62 15.0 10 to 15 592.14 587.14 1 PVC 3.48 VB-1-1D 602.14 604.52 32.0 27 to 32 575.14 570.14 1 PVC 2.38 VB-1-2 599.94 604.65 15.0 10 to 15 589.94 584.94 1 PVC 4.71 VB-1-2D 600.02 601.89 28.0 23 to 28 577.02 572.02 1 PVC 1.87 VB-1-3 599.64 603.61 15.0 10 to 15 589.64 584.64 1 PVC 3.97 VB-1-3D 599.55 601.95 27.5 22.5 to 27.5 577.05 572.05 1 PVC 2.40 VB-1-4 599.32 601.50 15.0 10 to 15 589.32 584.32 1 PVC 2.18 VB-1-4D 599.93 602.01 28.0 23 to 28 576.93 571.93 1 PVC 2.08 VB-1-5 600.17 603.85 15.0 10 to 15 590.17 585.17 1 PVC 3.68 VB-1-5D 600.26 602.29 28.0 23 to 28 577.26 572.26 1 PVC 2.03 VB-1-6 602.16 605.34 15.0 10 to 15 592.16 587.16 1 PVC 3.18 VB-1-6D 601.86 605.53 28.0 22 to 27 579.86 574.86 1 PVC 3.67 VB-1-7 600.60 603.62 15.0 10 to 15 590.60 585.60 1 PVC 3.02 VB-1-7D 600.48 602.80 26.2 21.2 to 26.2 579.28 574.28 1 PVC 2.32 VB-1-8 600.32 603.36 15.0 10 to 15 590.32 585.32 1 PVC 3.04 VB-1-8D 600.15 602.49 26.0 21 to 26 579.15 574.15 1 PVC 2.34 VB-1-9 598.92 601.86 15.0 10 to 15 588.92 583.92 1 PVC 2.94 VB-1-9D 598.69 601.61 27.0 22 to 27 576.69 571.69 1 PVC 2.92 VB-2-1 601.27 605.71 15.0 10 to 15 591.27 586.27 1 PVC 4.44 VB-2-2 596.82 600.16 15.0 10 to 15 586.82 581.82 1 PVC 3.34 VB-2-2D 596.49 598.95 30.5 24.5 to 29.5 571.99 566.99 1 PVC 2.46 VB-2-3 595.95 600.16 15.0 10 to 15 585.95 580.95 1 PVC 4.21 VB-2-4 596.08 600.82 15.0 10 to 15 586.08 581.08 1 PVC 4.74 VB-2-5 595.76 599.82 15.0 10 to 15 585.76 580.76 1 PVC 4.06 VB-2-5D 595.76 596.78 25.0 19 to 24 576.76 571.76 1 PVC 1.02 VB-2-6 596.01 601.44 15.0 10 to 15 586.01 581.01 1 PVC 5.43 CRA 016841 (12)

TABLE 4.1 Page 5 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 VB-2-6D 596.01 596.77 25.0 19 to 24 577.01 572.01 1 PVC 0.76 VB-2-7 600.51 602.04 15.0 10 to 15 590.51 585.51 1 PVC 1.53 VB-2-7D 600.51 602.28 26.0 20 to 25 580.51 575.51 1 PVC 1.77 VB-2-8 598.18 599.05 15.0 10 to 15 588.18 583.18 1 PVC 0.87 VB-2-9 596.31 599.48 14.0 9 to 14 587.31 582.31 1 PVC 3.17 VB-2-9D 596.26 599.93 28.0 21 to 26 575.26 570.26 1 PVC 3.67 VB-3-1 596.38 600.99 15.0 10 to 15 586.38 581.38 1 PVC 4.61 VB-3-2 596.49 601.51 15.0 10 to 15 586.49 581.49 1 PVC 5.02 VB-3-3 596.27 600.03 15.0 10 to 15 586.27 581.27 1 PVC 3.76 VB-3-4 596.18 601.37 15.0 10 to 15 586.18 581.18 1 PVC 5.19 VB-3-4D 596.18 600.82 25.0 20 to 25 576.18 571.18 1 PVC 4.64 VB-3-5 595.94 599.24 15.0 10 to 15 585.94 580.94 1 PVC 3.30 VB-3-6 595.89 599.18 15.0 10 to 15 585.89 580.89 1 PVC 3.29 VB-3-7 596.24 599.49 12.0 7 to 12 589.24 584.24 1 PVC 3.25 VB-3-7D 596.24 597.04 25.0 19 to 24 577.24 572.24 1 PVC 0.80 VB-3-8 596.44 599.51 12.0 7 to 12 589.44 584.44 1 PVC 3.07 VB-3-9D 595.68 596.62 25.0 19.5 to 24.5 576.18 571.18 1 PVC 0.94 VB-3-10 596.43 599.28 13.0 8 to 13 588.43 583.43 1 PVC 2.85 VB-3-10D 596.49 598.44 23.5 18.5 to 23.5 577.99 572.99 1 PVC 1.95 1

NGVD - National Geodetic Vertical datum 2

ft BGS - feet below ground surface 3

FT AGS - feet above ground surface 4

PVC - polyvinyl chloride 5

Well was abandoned and replaced Survey data incomplete CRA 016841 (12)

TABLE 4.2 Page 1 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

A-1 1/10/2006 597.00 9.01 587.99 A-1 1/11/2006 597.00 9.01 587.99 A-1D 1/10/2006 597.34 9.33 588.01 A-1D 1/11/2006 597.34 9.33 588.01 BL-01 11/15/2005 605.58 13.43 592.15 BL-01 1/5/2006 605.58 13.09 592.49 BL-02 11/15/2005 604.84 12.92 591.92 BL-02 1/5/2006 604.84 12.59 592.25 BL-03 11/15/2005 604.50 13.34 591.16 BL-03 1/5/2006 604.50 12.91 591.59 BL-04 11/15/2005 601.91 10.93 590.98 BL-04 1/5/2006 601.91 10.50 591.41 BL-05 11/15/2005 602.60 11.77 590.83 BL-05 1/5/2006 602.60 11.39 591.21 BL-06 11/15/2005 601.83 11.00 590.83 BL-06 1/5/2006 601.83 10.63 591.20 BL-07 11/15/2005 601.08 10.28 590.80 BL-07 1/5/2006 601.08 10.11 590.97 BL-08 11/15/2005 602.29 11.40 590.89 BL-08 1/5/2006 602.29 11.13 591.16 BL-09 11/15/2005 602.49 11.82 590.67 BL-09 12/21/2005 602.49 11.40 591.09 BL-09 12/23/2005 602.49 11.31 591.18 BL-09 1/5/2006 602.49 11.18 591.31 BL-09 1/11/2006 602.49 11.01 591.48 BL-09 2/1/2006 602.49 10.65 591.84 BL-09 2/10/2006 602.49 10.44 592.05 BL-09 2/15/2006 602.49 10.35 592.14 BL-09D 12/21/2005 600.36 9.40 590.96 BL-09D 12/23/2005 600.36 9.35 591.01 BL-09D 1/5/2006 600.36 9.21 591.15 BL-09D 1/11/2006 600.36 9.08 591.28 BL-09D 2/1/2006 600.36 8.68 591.68 BL-09D 2/10/2006 600.36 8.48 591.88 BL-09D 2/15/2006 600.36 8.37 591.99 BL-10 11/15/2005 605.37 14.29 591.08 BL-10 1/4/2006 605.37 14.03 591.34 BL-10D 12/15/2005 605.16 14.89 590.27 BL-10D 1/4/2006 605.16 13.81 591.35 BL-11 11/15/2005 600.65 9.70 590.95 BL-11 1/3/2006 600.65 9.41 591.24 BL-11D 12/15/2005 599.09 7.82 591.27 BL-11D 1/3/2006 599.09 7.56 591.53 BL-12 11/15/2005 601.60 10.41 591.19 BL-12 1/3/2006 601.60 10.05 591.55 BL-12D 12/15/2005 599.87 8.54 591.33 CRA 016841 (12)

TABLE 4.2 Page 2 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

BL-12D 1/3/2006 599.87 8.40 591.47 BL-13 11/15/2005 601.37 10.27 591.10 BL-13 1/3/2006 601.37 9.94 591.43 BL-13D 12/15/2005 600.82 9.39 591.43 BL-13D 1/3/2006 600.82 9.17 591.65 BL-14 11/15/2005 601.26 9.91 591.35 BL-14 1/3/2006 601.26 9.65 591.61 BL-14D 12/15/2005 597.46 8.49 588.97 BL-14D 1/3/2006 597.46 8.26 589.20 BL-15 11/15/2005 600.98 9.98 591.00 BL-15 1/3/2006 600.98 9.57 591.41 BL-15D 12/16/2005 598.50 6.20 592.30 BL-15D 1/3/2006 598.50 6.92 591.58 BL-16 11/15/2005 600.30 9.40 590.90 BL-16 1/3/2006 600.30 9.05 591.25 BL-16D 12/16/2005 598.17 7.10 591.07 BL-16D 1/3/2006 598.17 6.92 591.25 BL-17 12/1/2005 597.62 6.47 591.15 BL-17 12/5/2005 597.62 6.50 591.12 BL-17 1/3/2006 597.62 6.37 591.25 BL-17D 12/12/2005 598.11 7.21 590.90 BL-17D 1/3/2006 598.11 6.80 591.31 BL-18 12/1/2005 597.59 6.71 590.88 BL-18 1/3/2006 597.59 6.52 591.07 BL-19 12/1/2005 595.55 5.04 590.51 BL-19 1/3/2006 595.55 4.93 590.62 BL-20D 12/21/2005 600.45 9.40 591.05 BL-20D 12/23/2005 600.45 9.56 590.89 BL-20D 1/4/2006 600.45 9.16 591.29 C-1 12/12/2005 595.78 7.21 588.57 C-1 1/3/2006 595.78 6.78 589.00 C-1D 12/12/2005 595.87 7.35 588.52 C-1D 1/3/2006 595.87 6.79 589.08 C-2 1/24/2006 610.91 9.00 601.91 C-2 2/1/2006 610.91 8.50 602.41 C-2 2/10/2006 610.91 8.56 602.35 C-2 2/15/2006 610.91 8.70 602.21 C-2D 1/24/2006 609.03 7.09 601.94 C-2D 2/1/2006 609.03 6.75 602.28 C-2D 2/10/2006 609.03 6.76 602.27 C-2D 2/15/2006 609.03 6.90 602.13 D-1 12/6/2005 603.69 12.10 591.59 D-1 1/4/2006 603.69 11.90 591.79 D-1D 12/22/2005 603.77 12.10 591.67 D-1D 12/23/2005 603.77 12.04 591.73 D-1D 1/4/2006 603.77 12.00 591.77 CRA 016841 (12)

TABLE 4.2 Page 3 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

D-2 12/5/2005 601.92 10.52 591.40 D-2 1/4/2006 601.92 10.31 591.61 D-2D 12/22/2005 601.47 9.95 591.52 D-2D 1/4/2006 601.47 9.76 591.71 D-3 12/2/2005 602.48 11.05 591.43 D-3 1/4/2006 602.48 10.85 591.63 D-3D 12/23/2005 602.22 10.71 591.51 D-3D 1/4/2006 602.22 10.60 591.62 D-4 1/5/2006 602.55 11.09 591.46 D-5 12/2/2005 602.27 10.86 591.41 D-5 1/5/2006 602.27 10.57 591.70 F-1 12/12/2005 596.25 7.40 588.85 F-1 1/3/2006 596.25 7.19 589.06 F-1D 12/12/2005 596.19 7.35 588.84 F-1D 1/3/2006 596.19 7.10 589.09 F-2D 1/9/2006 597.26 7.26 590.00 F-3D 1/9/2006 597.36 8.57 588.79 F-3D 1/12/2006 597.36 8.67 588.69 F-4D 1/24/2006 599.59 10.87 588.72 F-5D 1/24/2006 595.96 6.65 589.31 F-6D 1/24/2006 597.28 9.26 588.02 F-7D 1/24/2006 596.37 8.48 587.89 F-8D 1/24/2006 598.42 9.70 588.72 G-1 12/6/2005 595.35 5.55 589.80 G-1 1/5/2006 595.35 5.03 590.32 G-2 12/6/2005 590.83 5.31 585.52 G-2 1/5/2006 590.83 4.81 586.02 G-2D 1/26/2006 590.65 3.65 587.00 G-3 12/6/2005 592.93 7.25 585.68 G-3 1/5/2006 592.93 6.85 586.08 MW-101 7/28/2005 602.77 12.25 590.52 MW-101 8/15/2005 602.77 11.01 591.76 MW-101 9/30/2005 602.77 11.49 591.28 MW-101 11/11/2005 602.77 11.67 591.10 MW-101 11/15/2005 602.77 11.60 591.17 MW-101 1/5/2006 602.77 11.35 591.42 MW-102 7/28/2005 605.70 13.17 592.53 MW-102 8/15/2005 605.70 13.78 591.92 MW-102 11/11/2005 605.70 13.79 591.91 MW-102 11/18/2005 605.70 13.79 591.91 MW-102 1/5/2006 605.70 13.78 591.92 MW-103 8/15/2005 598.84 6.90 591.94 MW-103 10/17/2005 598.84 7.78 591.06 MW-103 11/11/2005 598.84 7.81 591.03 MW-103 11/15/2005 598.84 7.70 591.14 MW-103 1/5/2006 598.84 7.75 591.09 CRA 016841 (12)

TABLE 4.2 Page 4 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

MW-104 7/28/2005 598.80 7.67 591.13 MW-104 8/15/2005 598.80 9.72 589.08 MW-104 11/11/2005 598.80 8.77 590.03 MW-104 11/18/2005 598.80 8.75 590.05 MW-104 1/5/2006 598.80 8.59 590.21 MW-105 7/28/2005 600.74 7.82 592.92 MW-105 8/15/2005 600.74 8.38 592.36 MW-105 9/30/2005 600.74 9.50 591.24 MW-105 10/17/2005 600.74 9.19 591.55 MW-105 11/11/2005 600.74 9.41 591.33 MW-105 11/15/2005 600.74 9.30 591.44 MW-105 1/4/2006 600.74 6.05 594.69 MW-105 1/5/2006 600.74 6.05 594.69 MW-105D 12/15/2005 598.20 6.76 591.44 MW-105D 12/16/2005 598.20 6.81 591.39 MW-105D 1/4/2006 598.20 6.48 591.72 MW-106 7/28/2005 602.73 9.13 593.60 MW-106 8/15/2005 602.73 9.66 593.07 MW-106 11/11/2005 602.73 10.71 592.02 MW-106 11/14/2005 602.73 10.82 592.31 MW-106 1/4/2006 602.73 10.42 591.91 MW-106 1/5/2006 602.73 6.48 596.25 MW-106D 12/16/2005 601.81 9.84 591.97 MW-106D 1/4/2006 601.81 9.52 592.29 MW-107 7/28/2005 603.24 9.62 593.62 MW-107 8/15/2005 603.24 9.93 593.31 MW-107 9/30/2005 603.24 10.41 592.83 MW-107 10/17/2005 603.24 10.55 592.69 MW-107 11/11/2005 603.24 10.70 592.54 MW-107 11/15/2005 603.24 10.71 592.53 MW-107 1/5/2006 603.24 10.42 592.82 MW-108 7/28/2005 603.10 10.72 592.38 MW-108 8/15/2005 603.10 10.89 592.21 MW-108 9/30/2005 603.10 11.31 591.79 MW-108 10/17/2005 603.10 11.42 591.68 MW-108 11/11/2005 603.10 11.24 591.86 MW-108 11/15/2005 603.10 11.18 591.92 MW-108 1/5/2006 603.10 12.90 590.20 MW-109 7/28/2005 601.23 9.70 591.53 MW-109 8/15/2005 601.23 9.91 591.32 MW-109 11/11/2005 601.23 10.58 590.65 MW-109 1/5/2006 601.23 10.41 590.82 MW-110 11/11/2005 607.27 19.16 588.11 MW-110 11/14/2005 607.27 19.28 587.99 MW-110 11/15/2005 607.27 19.19 588.08 MW-110 1/3/2006 607.27 19.46 587.81 CRA 016841 (12)

TABLE 4.2 Page 5 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

MW-110 1/4/2006 607.27 19.46 587.81 MW-111 11/11/2005 607.20 16.78 590.42 MW-111 11/15/2005 607.20 16.74 590.46 MW-111 1/4/2006 607.20 16.55 590.65 MW-111D 1/9/2006 605.05 14.35 590.70 MW-112 11/11/2005 602.62 12.19 590.43 MW-112 11/15/2005 602.62 12.13 590.49 MW-112 1/3/2006 602.62 11.77 590.85 MW-112 1/4/2006 602.62 11.77 590.85 MW-112D 1/9/2006 600.85 9.89 590.96 MW-113 11/11/2005 599.77 8.87 590.90 MW-113 11/15/2005 599.77 8.75 591.02 MW-113 12/5/2005 599.77 8.89 590.88 MW-113 1/3/2006 599.77 8.97 590.80 MW-113D 12/14/2005 596.90 6.12 590.78 MW-113D 1/3/2006 596.90 6.13 590.77 P-1 12/1/2005 595.59 5.08 590.51 P-1 1/5/2006 595.59 5.02 590.57 P-2 12/2/2005 596.27 5.95 590.32 P-2 1/3/2006 596.27 5.81 590.46 P-2 1/4/2006 596.27 5.81 590.46 P-2D 12/12/2005 596.55 6.26 590.29 P-2D 1/3/2006 596.55 6.08 590.47 P-2D 1/4/2006 596.55 6.08 590.47 P-3 12/2/2005 596.26 6.08 590.18 P-3 1/5/2006 596.26 5.91 590.35 P-4 12/1/2005 597.14 6.41 590.73 P-4 12/6/2005 597.14 6.50 590.64 P-4 1/3/2006 597.14 6.41 590.73 P-4 1/11/2006 597.14 6.31 590.83 P-4 1/18/2006 597.14 6.28 590.86 P-4 1/25/2006 597.14 6.21 590.93 P-4 2/1/2006 597.14 5.95 591.19 P-4 2/10/2006 597.14 5.98 591.16 P-4 2/15/2006 597.14 6.00 591.14 P-4D 12/23/2005 599.22 8.68 590.54 P-4D 1/3/2006 599.22 8.63 590.59 P-4D 1/11/2006 599.22 8.55 590.67 P-4D 1/18/2006 599.22 8.50 590.72 P-4D 1/25/2006 599.22 8.48 590.74 P-4D 2/1/2006 599.22 8.06 591.16 P-4D 2/10/2006 599.22 8.20 591.02 P-4D 2/15/2006 599.22 8.28 590.94 P-4D 2/22/2006 599.22 8.16 591.06 P-5 12/1/2005 597.06 6.48 590.58 P-5 1/3/2006 597.06 6.45 590.61 CRA 016841 (12)

TABLE 4.2 Page 6 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

P-5D 12/23/2005 599.37 10.22 589.15 P-5D 1/3/2006 599.37 8.91 590.46 P-6 12/1/2005 597.85 7.30 590.55 P-6 1/5/2006 597.85 7.41 590.44 P-6 1/18/2006 597.85 6.18 591.67 P-7 12/1/2005 600.24 9.58 590.66 P-7 1/5/2006 600.24 9.52 590.72 P-8 12/1/2005 596.24 5.63 590.61 P-8 12/6/2005 596.24 5.74 590.50 P-8 1/5/2006 596.24 5.59 590.65 P-9 12/5/2005 599.19 8.75 590.44 P-9 1/5/2006 599.19 8.44 590.75 P-10 12/5/2005 596.58 6.54 590.04 P-10 1/5/2006 596.58 6.23 590.35 P-11 12/5/2005 596.23 6.55 589.68 P-11 1/5/2006 596.23 6.20 590.03 P-12 12/5/2005 596.13 6.79 589.34 P-12 1/5/2006 596.13 6.49 589.64 P-13D 12/23/2005 598.76 8.34 590.42 P-13D 1/3/2006 598.76 8.25 590.51 P-13D 1/11/2006 598.76 5.26 593.50 P-13D 1/18/2006 598.76 5.20 593.56 P-13D 1/25/2006 598.76 8.16 590.60 P-13D 2/1/2006 598.76 7.90 590.86 P-13D 2/10/2006 598.76 7.98 590.78 P-13D 2/15/2006 598.76 8.00 590.76 P-13D 2/22/2006 598.76 8.02 590.74 P-14 1/24/2006 599.14 6.40 592.74 P-14D 1/24/2006 598.50 7.89 590.61 PS-1 12/22/2005 546.13 6.77 539.36 PS-1 1/4/2006 546.13 7.88 538.25 PS-2 12/22/2005 546.76 10.21 536.55 PS-2 1/4/2006 546.76 9.65 537.11 PS-3 12/22/2005 550.09 10.65 539.44 PS-3 12/23/2005 550.09 14.15 535.94 PS-3 1/4/2006 550.09 14.06 536.03 PS-4 1/9/2006 548.90 10.90 538.00 PS-5 1/10/2006 550.24 10.91 539.33 PS-6 1/10/2006 547.40 7.51 539.89 RW-1 12/1/2005 599.36 7.42 591.94 RW-1 1/5/2006 599.36 8.23 591.13 RW-2 12/1/2005 599.30 8.68 590.62 RW-2 1/5/2006 599.30 8.44 590.86 RW-3 12/2/2005 599.19 8.48 590.71 RW-3 1/5/2006 599.19 8.37 590.82 RW-4 12/2/2005 598.77 8.12 590.65 CRA 016841 (12)

TABLE 4.2 Page 7 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

RW-4 1/5/2006 598.77 7.97 590.80 S-1 12/5/2005 595.60 7.50 588.10 S-1 1/5/2006 595.60 7.06 588.54 S-1D 1/26/2006 596.92 7.87 589.05 S-2 12/5/2005 593.32 5.22 588.10 S-2 1/3/2006 593.32 4.68 588.64 S-2 1/5/2006 593.32 4.70 588.62 S-2 2/1/2006 593.32 3.80 589.52 S-2 2/10/2006 593.32 3.98 589.34 S-2 2/15/2006 593.32 4.04 589.28 S-2 2/22/2006 593.32 4.08 589.24 S-2D 12/12/2005 593.98 6.14 587.84 S-2D 1/3/2006 593.98 5.30 588.68 S-2D 1/5/2006 593.98 5.35 588.62 S-2D 2/1/2006 593.98 4.37 589.61 S-2D 2/10/2006 593.98 4.56 589.42 S-2D 2/15/2006 593.98 4.62 589.36 S-2D 2/22/2006 593.98 4.65 589.33 S-3 12/5/2005 593.37 5.29 588.08 S-3 1/5/2006 593.37 4.78 588.59 S-4 12/5/2005 594.63 5.69 588.94 S-4 1/5/2006 594.63 5.25 589.38 S-4D 1/26/2006 596.67 7.75 588.92 S-5 12/5/2005 593.44 4.25 589.19 S-5 1/5/2006 593.44 3.85 589.59 S-6 12/5/2005 595.57 6.72 588.85 S-6 1/5/2006 595.57 6.31 589.26 S-7 1/24/2006 594.73 4.98 589.75 S-7D 1/24/2006 596.53 6.80 589.73 SG-1 8/15/2005 594.08 0.19 593.89 SG-2 8/15/2005 594.85 0.15 594.70 SG-3 8/15/2005 594.51 0.00 594.51 SG-A 2/1/2006 589.78 1.39 591.17 SG-A 2/10/2006 589.78 1.40 591.18 SG-A 2/15/2006 589.78 1.20 590.98 SG-B 1/25/2006 589.75 1.00 590.75 SG-B 2/1/2006 589.75 1.10 590.85 SG-B 2/10/2006 589.75 1.19 590.94 SG-B 2/15/2006 589.75 1.19 590.94 SG-C 1/25/2006 585.93 1.01 586.94 SG-C 2/1/2006 585.93 1.11 587.04 SG-C 2/10/2006 585.93 1.21 587.14 SG-C 2/15/2006 585.93 1.50 587.43 VB-1-1D 12/16/2005 604.52 12.34 592.18 VB-1-1D 1/4/2006 604.52 12.30 592.22 VB-1-2 11/15/2005 604.65 12.75 591.90 CRA 016841 (12)

TABLE 4.2 Page 8 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

VB-1-2 1/5/2006 604.65 12.39 592.26 VB-1-2D 1/10/2006 601.89 9.40 592.49 VB-1-2D 1/13/2006 601.89 9.40 592.49 VB-1-3 11/15/2005 603.61 11.97 591.64 VB-1-3 1/5/2006 603.61 11.72 591.89 VB-1-3D 1/10/2006 601.95 9.67 592.28 VB-1-3D 1/13/2006 601.95 9.65 592.30 VB-1-4 11/15/2005 601.50 10.62 590.88 VB-1-4 1/5/2006 601.50 10.31 591.19 VB-1-4D 1/13/2006 602.01 8.90 593.11 VB-1-5 11/15/2005 603.85 12.52 591.33 VB-1-5 1/5/2006 603.85 12.21 591.64 VB-1-5D 1/10/2006 602.29 10.30 593.55 VB-1-5D 1/13/2006 602.29 10.29 592.00 VB-1-6 11/22/2005 605.34 14.38 590.96 VB-1-6 1/5/2006 605.34 14.11 591.23 VB-1-6D 1/10/2006 605.53 14.20 591.33 VB-1-6D 1/13/2006 605.53 14.30 591.23 VB-1-7 11/22/2005 603.62 12.44 591.18 VB-1-7 1/5/2006 603.62 12.15 591.47 VB-1-7D 1/9/2006 602.80 11.20 591.60 VB-1-8 11/22/2005 603.36 12.15 591.21 VB-1-8 1/5/2006 603.36 11.75 591.61 VB-1-8D 1/9/2006 602.49 10.52 591.97 VB-1-9 11/22/2005 601.86 10.76 591.10 VB-1-9 1/5/2006 601.86 10.37 591.49 VB-1-9D 1/10/2006 601.61 9.84 591.77 VB-1-9D 1/13/2006 601.61 10.91 590.70 VB-2-1 11/15/2005 605.71 14.87 590.84 VB-2-1 1/5/2006 605.71 14.57 591.14 VB-2-2 11/15/2005 600.16 8.80 591.36 VB-2-2 12/5/2005 600.16 8.89 591.27 VB-2-2 1/4/2006 600.16 8.60 591.56 VB-2-2D 12/21/2005 598.95 8.05 590.90 VB-2-2D 12/23/2005 598.95 8.00 590.95 VB-2-2D 1/4/2006 598.95 7.83 591.12 VB-2-3 11/15/2005 600.16 9.03 591.13 VB-2-3 1/5/2006 600.16 9.22 590.94 VB-2-4 11/15/2005 600.82 10.00 590.82 VB-2-4 1/5/2006 600.82 9.95 590.87 VB-2-5 11/15/2005 599.82 9.20 590.62 VB-2-5 1/3/2006 599.82 9.30 590.52 VB-2-5D 12/14/2005 596.78 6.02 590.76 VB-2-5D 1/3/2006 596.78 6.61 590.17 VB-2-6 11/15/2005 601.44 10.80 590.64 VB-2-6 12/5/2005 601.44 10.93 590.51 CRA 016841 (12)

TABLE 4.2 Page 9 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

VB-2-6 1/3/2006 601.44 7.94 593.50 VB-2-6D 12/14/2005 596.77 6.12 590.65 VB-2-6D 1/3/2006 596.77 6.11 590.66 VB-2-7 12/14/2005 602.04 11.19 590.85 VB-2-7 1/4/2006 602.04 10.99 591.05 VB-2-7D 12/14/2005 602.28 11.39 590.89 VB-2-7D 1/4/2006 602.28 11.26 591.02 VB-2-8 12/14/2005 599.05 8.27 590.78 VB-2-8 1/5/2006 599.05 8.02 591.03 VB-2-9 1/10/2006 599.48 8.49 590.99 VB-2-9 1/12/2006 599.48 8.49 590.99 VB-2-9D 1/10/2006 599.93 9.69 590.24 VB-2-9D 1/12/2006 599.93 9.69 590.24 VB-3-1 11/15/2005 600.99 9.83 591.16 VB-3-1 1/5/2006 600.99 9.75 591.24 VB-3-2 11/15/2005 601.51 10.22 591.29 VB-3-2 1/5/2006 601.51 9.98 591.53 VB-3-3 11/15/2005 600.03 9.05 590.98 VB-3-3 1/5/2006 600.03 8.79 591.24 VB-3-4 11/15/2005 601.37 10.58 590.79 VB-3-4 12/5/2005 601.37 10.43 590.94 VB-3-4 1/3/2006 601.37 10.33 591.04 VB-3-4D 12/14/2005 600.82 9.79 591.03 VB-3-4D 1/3/2006 600.82 9.57 591.25 VB-3-5 11/22/2005 599.24 9.44 589.80 VB-3-5 1/5/2006 599.24 7.94 591.30 VB-3-6 11/22/2005 599.18 8.60 590.58 VB-3-6 1/5/2006 599.18 8.28 590.90 VB-3-7 12/2/2005 599.49 8.19 591.30 VB-3-7 12/14/2005 599.49 5.72 593.77 VB-3-7 1/3/2006 599.49 7.91 591.58 VB-3-7D 12/14/2005 597.04 5.72 591.32 VB-3-7D 1/3/2006 597.04 5.45 591.59 VB-3-8 12/2/2005 599.51 8.20 591.31 VB-3-8 1/5/2006 599.51 7.82 591.69 VB-3-9D 12/13/2005 596.62 6.37 590.25 VB-3-9D 1/4/2006 596.62 5.64 590.98 VB-3-10 12/16/2005 599.28 8.22 591.06 VB-3-10 1/3/2006 599.28 7.88 591.40 VB-3-10D 12/16/2005 598.44 7.28 591.16 VB-3-10D 1/3/2006 598.44 7.07 591.37 1

Water level data through March 1, 2006 2

ft amsl - feet above mean sea level 3

ft btoc - feet below top of casing CRA 016841 (12)

TABLE 4.3 Page 1 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 A-1 1/11/06 9.01 10 7.11 766 11.67

• slightly cloudy peristaltic A-1 1/11/06 12 7.06 802 11.61

• slightly cloudy peristaltic A-1 1/11/06 14 7.01 814 11.48

• clear peristaltic A-1D 1/11/06 9.33 10 6.64 555 10.22

• slightly cloudy peristaltic A-1D 1/11/06 13 7.15 559 10.86

• slightly cloudy peristaltic A-1D 1/11/06 16 7.20 560 10.89

• slightly cloudy peristaltic BL-01 11/17/05 13.43 5 6.59 345 15.74

• cloudy peristaltic BL-01 11/17/05 10 6.62 348 15.61

• slightly cloudy peristaltic BL-01 11/17/05 15 6.64 339 15.60

• slightly cloudy peristaltic BL-02 11/17/05 12.92 5 6.48 425 13.36

• cloudy peristaltic BL-02 11/17/05 10 6.43 421 13.20

• slightly cloudy peristaltic BL-02 11/17/05 15 6.39 416 13.17

• clear peristaltic BL-02 11/17/05 20 6.40 415 13.21

• clear peristaltic BL-03 11/18/05 13.34 5 7.25 280 17.73

• cloudy peristaltic BL-03 11/18/05 10 7.06 296 17.75

• slightly cloudy peristaltic BL-03 11/18/05 15 7.01 294 17.78

• clear peristaltic BL-04 11/18/05 10.93 5 6.70 499 17.42

• clear peristaltic BL-04 11/18/05 10 6.62 524 17.41

• clear peristaltic BL-04 11/18/05 15 6.60 520 17.44

• clear peristaltic BL-05 11/18/05 11.77 5 6.73 694 15.57

• cloudy peristaltic BL-05 11/18/05 10 6.59 697 15.58

• cloudy peristaltic BL-05 11/18/05 15 6.54 687 15.46

• slightly cloudy peristaltic BL-06 11/18/05 11.00 5 6.70 435 15.33

• slightly cloudy peristaltic BL-06 11/18/05 10 6.61 436 15.38

• slightly cloudy peristaltic BL-06 11/18/05 15 6.57 437 15.37

• slightly cloudy peristaltic CRA 016841 (12)

TABLE 4.3 Page 2 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-07 11/18/05 10.28 5 6.97 656 15.75

• slightly cloudy peristaltic BL-07 11/18/05 10 6.77 648 15.77

• clear peristaltic BL-07 11/18/05 15 6.71 643 15.76

• clear peristaltic BL-08 11/18/05 11.40 5 7.40 220 14.91

• slightly cloudy peristaltic BL-08 11/18/05 10 7.32 217 14.92

• slightly cloudy peristaltic BL-08 11/18/05 15 7.28 215 14.92

• slightly cloudy peristaltic BL-09 11/18/05 11.82 1 * * *

• sand filled well screen- DRY

• BL-9 12/23/05 11.31 10 8.50 335 13.90

• slightly cloudy peristaltic BL-9 12/23/05 13 8.50 346 14.20

• slightly cloudy peristaltic BL-9 12/23/05 16 8.50 346 14.20

• clear peristaltic BL-9 1/11/06 11.01 10 8.38 369 14.20

• clear peristaltic BL-9 1/11/06 13 8.40 362 13.90

• clear peristaltic BL-9 1/11/06 16 8.40 361 13.80

• clear peristaltic BL-9 1/18/06

• 10 7.00 467 12.39

• clear peristaltic BL-9 1/18/06 13 7.18 466 12.37

• clear peristaltic BL-9 1/18/06 16 7.31 466 12.30

• clear peristaltic BL-9 2/15/06 10.35 10 7.25 307 13.50

• clear peristaltic BL-9 2/15/06 13 7.26 307 13.60

• clear peristaltic BL-9 2/15/06 16 7.27 307 13.70

• clear peristaltic BL-09 1/25/06

• 10 8.33 359 9.90 51.7 clear peristaltic BL-09 1/25/06 15 8.38 346 10.40 36.2 clear peristaltic BL-09 1/25/06 20 8.37 348 10.50 19.6 clear peristaltic BL-09 2/1/06 10.65 10 7.22 319 14.20

• clear peristaltic BL-09 2/1/06 13 7.24 313 14.50

• clear peristaltic BL-09 2/1/06 16 7.26 312 14.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 3 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-09 2/9/06 10.44 5 6.61 414 12.18

• clear peristaltic BL-09 2/9/06 10 6.51 413 12.21

• clear peristaltic BL-09 2/9/06 15 6.52 413 12.29

• clear peristaltic BL-09 2/22/06 10.23 10 7.34 278 11.90

• clear peristaltic BL-09 2/22/06 13 7.23 186 12.30

• clear peristaltic BL-09 2/22/06 16 7.20 186 12.30

• clear peristaltic BL-09 3/1/06 8.21 10 8.01 192 13.80

• clear peristaltic BL-09 3/1/06 13 8.01 192 13.80

• clear peristaltic BL-09 3/1/06 16 8.01 192 13.80

• clear peristaltic BL-09 3/7/06 10.20 10 8.00 190 13.00

• clear peristaltic BL-09 3/7/06 13 7.99 190 13.10

• clear peristaltic BL-09 3/7/06 16 7.99 190 13.10

• clear peristaltic BL-9D 12/23/05 9.35 10 7.95 560 13.02

• slightly cloudy peristaltic BL-9D 12/23/05 13 7.70 569 13.28

• clear peristaltic BL-9D 12/23/05 16 7.57 569 13.32

• clear peristaltic BL-9D 1/11/06 9.08 10 8.05 515 13.90

• clear peristaltic BL-9D 1/11/06 13 7.97 519 13.90

• clear peristaltic BL-9D 1/11/06 16 7.95 519 13.90

• clear peristaltic BL-9D 1/18/06

• 10 6.76 651 12.51

• clear peristaltic BL-9D 1/18/06 12 6.70 640 12.09

• clear peristaltic BL-9D 1/18/06 14 6.72 641 12.09

• clear peristaltic BL-9D 2/15/06 8.37 10 7.18 443 14.10

• clear peristaltic BL-9D 2/15/06 13 7.18 444 14.30

• clear peristaltic BL-9D 2/15/06 16 7.18 444 14.30

• clear peristaltic BL-09D 1/25/06

• 10 8.30 485 10.20 51 clear peristaltic BL-09D 1/25/06 15 8.28 491 10.70 32.8 clear peristaltic BL-09D 1/25/06 20 8.27 499 11.20 26.7 clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 4 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-09D 2/1/06 8.68 10 7.07 450 14.90

• clear peristaltic BL-09D 2/1/06 13 7.11 451 15.00

• clear peristaltic BL-09D 2/1/06 16 7.13 450 15.10

• clear peristaltic BL-09D 2/9/06 8.48 5 6.22 632 13.06

• clear peristaltic BL-09D 2/9/06 10 6.18 635 13.17

• clear peristaltic BL-09D 2/9/06 15 6.18 636 13.20

• clear peristaltic BL-09D 2/22/06 8.27 12 6.95 377 12.60

• clear peristaltic BL-09D 2/22/06 15 6.88 377 12.60

• clear peristaltic BL-09D 2/22/06 18 6.86 379 12.70

• clear peristaltic BL-09D 3/1/06 8.21 10 7.81 478 14.20

• clear peristaltic BL-09D 3/1/06 13 7.78 478 14.20

• clear peristaltic BL-09D 3/1/06 16 7.75 478 14.20

• clear peristaltic BL-09D 3/7/06 8.25 12 7.72 464 13.40

• clear peristaltic BL-09D 3/7/06 15 7.68 466 13.50

• clear peristaltic BL-09D 3/7/06 18 7.61 466 13.50

• clear peristaltic BL-10 11/17/05 14.29 5 7.21 210 15.74

• slightly cloudy peristaltic BL-10 11/17/05 10 7.20 208 15.70

• clear peristaltic BL-10 11/17/05 15 7.22 207 15.66

• clear peristaltic BL-10 1/4/06 14.03 10 7.11 414 12.19

• clear peristaltic BL-10 1/4/06 13 7.32 236 13.55

• clear peristaltic BL-10 1/4/06 16 7.39 235 13.50

• clear peristaltic BL-10D 1/4/06 13.81 10 7.01 670 13.94

• slightly cloudy peristaltic BL-10D 1/4/06 13 7.04 668 14.00

• clear peristaltic BL-10D 1/4/06 16 7.06 669 14.03

• clear peristaltic BL-11 11/17/05 9.70 5 6.80 425 16.64

• slightly cloudy peristaltic BL-11 11/17/05 10 6.66 423 16.75

• clear peristaltic BL-11 11/17/05 15 6.61 422 16.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 5 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-11 1/3/06 9.41 5 7.21 371 13.80 36.9 clear peristaltic BL-11 1/3/06 8 7.21 373 14.10 28.2 clear peristaltic BL-11 1/3/06 11 7.19 375 14.30 19.9 clear peristaltic BL-11D 12/15/05 7.82 30 7.60 414 14.70

• clear peristaltic BL-11D 12/15/05 33 7.50 411 14.80

• clear peristaltic BL-11D 12/15/05 36 7.39 412 14.39

• clear peristaltic BL-11D 1/3/06 7.56 5 7.18 364 14.70 56.8 cloudy peristaltic BL-11D 1/3/06 8 7.17 366 14.60 47.9 cloudy peristaltic BL-11D 1/3/06 11 7.17 361 14.70 36.2 clear peristaltic BL-12 11/17/05 10.41 5 6.89 360 16.73

• cloudy peristaltic BL-12 11/17/05 10 6.78 357 16.74

• slightly cloudy peristaltic BL-12 11/17/05 15 6.73 355 16.72

• clear peristaltic BL-12 1/3/06 10.05 10 6.81 335 14.23

• slightly cloudy peristaltic BL-12 1/3/06 13 6.83 329 14.22

• slightly cloudy peristaltic BL-12 1/3/06 16 6.82 315 14.25

• clear peristaltic BL-12D 12/15/05 8.54 24 7.35 418 14.89

• clear peristaltic BL-12D 12/15/05 27 7.35 419 14.73

• clear peristaltic BL-12D 12/15/05 30 7.34 418 14.85

• clear peristaltic BL-12D 1/3/06 8.40 10 6.88 429 14.65

• clear peristaltic BL-12D 1/3/06 13 6.82 427 14.68

• clear peristaltic BL-12D 1/3/06 16 6.77 418 14.70

• clear peristaltic BL-13 11/17/05 10.27 5 6.87 515 18.12

• cloudy peristaltic BL-13 11/17/05 10 6.68 505 17.95

• slightly cloudy peristaltic BL-13 11/17/05 15 6.62 502 18.08

• slightly cloudy peristaltic BL-13 1/3/06 9.94 10 7.24 423 13.10 32.7 clear peristaltic BL-13 1/3/06 13 7.21 415 13.60 24.2 clear peristaltic BL-13 1/3/06 16 7.19 415 13.90 17.8 clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 6 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 Bl-13D 12/15/05 9.39 42 7.07 470 15.28

• clear peristaltic Bl-13D 12/15/05 45 7.10 471 15.24

• clear peristaltic Bl-13D 12/15/05 48 7.12 472 15.18

• clear peristaltic BL-13D 1/3/06 9.17 5 7.17 399 14.80 47.1 cloudy peristaltic BL-13D 1/3/06 8 7.16 400 14.70 34.3 clear peristaltic BL-13D 1/3/06 11 7.15 403 14.50 26.7 clear peristaltic BL-14 11/17/05 9.91 5 7.01 235 17.53

• cloudy peristaltic BL-14 11/17/05 10 6.97 231 17.62

• cloudy peristaltic BL-14 11/17/05 15 6.94 289 17.42

• cloudy peristaltic BL-14 11/17/05 20 6.93 287 17.44

• slightly cloudy peristaltic BL-14 1/3/06 9.65 10 6.93 301 14.58

• clear peristaltic BL-14 1/3/06 13 6.99 302 14.62

• clear peristaltic BL-14 1/3/06 16 6.99 303 14.62

• clear peristaltic BL-14D 12/15/05 28.71 45 7.07 463 14.77

• clear peristaltic BL-14D 12/15/05 48 7.07 464 14.77

• clear peristaltic BL-14D 12/15/05 51 7.08 465 14.86

• clear peristaltic BL-14D 1/3/06 8.26 10 6.53 519 15.04

• slightly cloudy peristaltic BL-14D 1/3/06 13 6.63 520 15.21

• slightly cloudy peristaltic BL-14D 1/3/06 16 6.61 520 15.35

• clear peristaltic BL-15 11/17/05 9.98 5 7.08 350 17.20

• slightly cloudy peristaltic BL-15 11/17/05 10 6.99 347 17.37

• clear peristaltic BL-15 11/17/05 15 6.95 354 17.25

• clear peristaltic BL-15 1/3/06 9.57 10 7.26 271 13.50 33.6 clear peristaltic BL-15 1/3/06 13 7.26 262 14.10 22.6 clear peristaltic BL-15 1/3/06 16 7.26 265 14.20 16.8 clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 7 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-15D 12/16/05 6.20 10 8.20 309 14.60

• clear peristaltic BL-15D 12/16/05 13 8.15 310 15.20

• clear peristaltic BL-15D 12/16/05 16 8.12 312 15.20

• clear peristaltic BL-15D 1/3/06 6.92 5 7.24 299 14.70 18.2 clear peristaltic BL-15D 1/3/06 8 7.23 316 14.80 15.6 clear peristaltic BL-15D 1/3/06 11 7.22 302 15.20 11.4 clear peristaltic BL-16 11/17/05 9.40 5 6.57 580 17.47

• slightly cloudy peristaltic BL-16 11/17/05 10 6.45 571 17.50

• clear peristaltic BL-16 11/17/05 15 6.47 570 17.46

• clear peristaltic BL-16 1/3/06 9.05 10 6.70 655 13.28

• clear peristaltic BL-16 1/3/06 13 6.64 653 13.33

• clear peristaltic BL-16 1/3/06 16 6.61 652 13.35

• clear peristaltic BL-16D 12/16/05 7.60 10 8.39 256 13.00

• clear peristaltic BL-16D 12/16/05 13 8.35 251 14.20

• clear peristaltic BL-16D 12/16/05 16 8.33 250 14.70

• clear peristaltic BL-16D 1/3/06 6.92 10 6.75 301 14.53

• slightly cloudy peristaltic BL-16D 1/3/06 13 6.91 301 14.63

• clear peristaltic BL-16D 1/3/06 16 6.93 303 14.62

• clear peristaltic BL-17 12/1/05 6.47 10 7.43 412 14.30

• slightly cloudy, gray peristaltic BL-17 12/1/05 15 7.37 409 14.80

• slightly cloudy, gray peristaltic BL-17 12/1/05 20 7.32 407 15.20

• slightly cloudy, gray peristaltic BL-17 12/5/05 6.50 5 7.28 355 14.40 *

• peristaltic BL-17 12/5/05 10 7.23 350 14.20 *

• peristaltic BL-17 12/5/05 15 7.26 360 14.20 *

• peristaltic BL-17 1/3/06 6.37 10 7.65 275 14.00

• clear peristaltic BL-17 1/3/06 15 7.61 275 14.20

• clear peristaltic BL-17 1/3/06 20 7.61 274 14.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 8 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-17D 12/12/05 7.21 10 8.37 222 14.60

• cloudy peristaltic BL-17D 12/12/05 13 8.29 215 15.10

• cloudy peristaltic BL-17D 1/3/06 6.80 10 8.11 209 14.60

• clear peristaltic BL-17D 1/3/06 15 8.15 207 14.70

• clear peristaltic BL-17D 1/3/06 20 8.16 207 14.80

• clear peristaltic BL-18 12/1/05 6.71 10 6.94 529 14.10

• cloudy, gray peristaltic BL-18 12/1/05 15 7.28 519 14.70

• cloudy, gray peristaltic BL-18 12/1/05 20 7.40 521 14.70

• slightly cloudy, gray peristaltic BL-18D 2/7/06 7.07 10 7.52 244 17.40

• cloudy peristaltic BL-18D 2/7/06 13 7.42 179 18.40

• slightly cloudy peristaltic BL-18D 2/7/06 16 7.39 177 18.40

• clear peristaltic BL-19 12/1/05 5.04 10 7.44 565 12.30

• cloudy, gray peristaltic BL-19 12/1/05 15 7.37 556 12.20

• slightly cloudy, gray peristaltic BL-19 12/1/05 20 7.36 555 12.00

• slightly cloudy, gray peristaltic BL-19D 2/7/06 4.90 10 7.50 270 14.60

• cloudy peristaltic BL-19D 2/7/06 13 7.39 261 14.50

• slightly cloudy peristaltic BL-19D 2/7/06 16 7.35 256 15.10

• slightly cloudy peristaltic BL-20D 12/23/05 9.56 10 7.54 411 14.33

• clear peristaltic BL-20D 12/23/05 12 7.50 398 14.48

• clear peristaltic BL-20D 12/23/05 14 7.45 390 14.50

• clear peristaltic BL-20D 1/4/06 9.16 10 7.36 320 13.10 28.1 clear peristaltic BL-20D 1/4/06 13 7.31 296 13.60 21.7 clear peristaltic BL-20D 1/4/06 16 7.26 310 13.90 17.2 clear peristaltic C-1 12/12/05 7.21 10 7.46 584 13.60

• slightly cloudy peristaltic C-1 12/12/05 13 7.45 584 13.40

• clear peristaltic C-1 12/12/05 16 7.41 585 13.53

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 9 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 C-1D 12/12/05 7.35 10 7.83 551 13.30

• cloudy peristaltic C-1D 12/12/05 13 7.81 556 13.20

• cloudy peristaltic C-1D 12/12/05 16 7.73 563 12.50

• cloudy peristaltic C-1D 1/3/06 6.79 5 7.70 584 13.10

• clear peristaltic C-1D 1/3/06 10 7.71 578 13.10

• clear peristaltic C-1D 1/3/06 15 7.73 578 13.10

• clear peristaltic C-2 1/24/06 9.00 7 6.31 456 10.87

• clear peristaltic C-2 1/24/06 10 6.31 450 10.93

• clear peristaltic C-2 1/24/06 13 5.97 449 10.93

• clear peristaltic C-2 2/1/06 8.50 10 6.73 305 12.80

• clear peristaltic C-2 2/1/06 13 6.58 302 12.80

• clear peristaltic C-2 2/1/06 16 6.49 306 12.80

• clear peristaltic C-2 2/9/06 8.56 5 5.48 392 10.11

• slightly cloudy peristaltic C-2 2/9/06 10 5.42 394 10.05

• slightly cloudy peristaltic C-2 2/9/06 15 5.37 395 9.95

• clear peristaltic C-2 2/15/06 8.70 10 6.55 294 11.50

• clear peristaltic C-2 2/15/06 12 6.53 294 11.60

• clear peristaltic C-2 2/15/06 14 6.52 294 11.60

• clear peristaltic C-2 2/22/06 8.63 12 5.96 193 11.00

• clear peristaltic C-2 2/22/06 15 5.95 194 10.90

• clear peristaltic C-2 2/22/06 18 5.93 196 10.90

• clear peristaltic C-2 3/2/06

• 10 6.86 191 11.10

• clear peristaltic C-2 3/2/06 13 6.80 192 11.10

• clear peristaltic C-2 3/2/06 16 6.77 193 11.10

• clear peristaltic C-2 3/7/06 8.60 5 6.64 420 9.70 *

• peristaltic C-2 3/7/06 10 6.29 417 9.47 *

• peristaltic C-2 3/7/06 15 6.25 417 9.53 *

• peristaltic CRA 016841 (12)

TABLE 4.3 Page 10 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 C-2D 1/24/06 7.09 10 6.84 657 12.13

• clear peristaltic C-2D 1/24/06 13 6.76 665 12.13

• clear peristaltic C-2D 1/24/06 16 6.70 664 12.10

• clear peristaltic C-2D 2/1/06 6.75 10 7.15 443 13.30

• slightly cloudy peristaltic C-2D 2/1/06 13 7.11 442 13.30

• slightly cloudy peristaltic C-2D 2/1/06 16 7.10 441 13.50

• clear peristaltic C-2D 2/9/06 6.76 5 6.26 621 10.80

• very cloudy peristaltic C-2D 2/9/06 10 6.08 618 11.11

• slightly cloudy peristaltic C-2D 2/9/06 15 6.03 620 10.88

• clear peristaltic C-2D 2/15/06 6.90 10 7.14 432 12.70

• clear peristaltic C-2D 2/15/06 13 7.11 436 12.70

• clear peristaltic C-2D 2/15/06 16 7.11 436 12.70

• clear peristaltic C-2D 2/22/06 6.85 10 6.64 372 11.60

• clear peristaltic C-2D 2/22/06 13 6.56 371 11.80

• clear peristaltic C-2D 2/22/06 16 6.54 370 11.90

• clear peristaltic C-2D 3/2/06

• 10 7.22 185 12.20

• clear peristaltic C-2D 3/2/06 13 7.01 185 12.20

• clear peristaltic C-2D 3/2/06 16 7.00 185 12.20

• clear peristaltic C-2D 3/7/06 6.82 10 6.53 654 10.42 *

• peristaltic C-2D 3/7/06 15 6.81 664 10.71 *

• peristaltic C-2D 3/7/06 20 6.82 665 10.76 *

• peristaltic C-2D 3/7/06 25 6.84 665 10.80 *

• peristaltic D-1 12/6/05 12.10 10 6.96 480 13.10 *

• peristaltic D-1 12/6/05 15 6.95 486 13.10 *

• peristaltic D-1 12/6/05 20 6.95 482 12.90 *

• peristaltic CRA 016841 (12)

TABLE 4.3 Page 11 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 D-1 1/4/06 11.90 10 7.71 513 12.00 104

• peristaltic D-1 1/4/06 15 7.63 512 12.00 19.7

• peristaltic D-1 1/4/06 20 7.61 512 12.00 *

• peristaltic D1-1D 1/4/06 12.00 10 6.83 1053 11.45

• clear peristaltic D1-1D 1/4/06 12 6.81 1057 11.55

• clear peristaltic D1-1D 1/4/06 14 6.75 1058 11.64

• clear peristaltic D-1D 12/23/05 12.04 10 7.70 770 13.20

• slightly cloudy peristaltic D-1D 12/23/05 13 7.65 776 13.10

• slightly cloudy peristaltic D-1D 12/23/05 16 7.64 780 13.00

• clear peristaltic D-1D 12/23/05 D-2 12/5/05 10.52 10 6.95 764 10.20 *

• peristaltic D-2 12/5/05 15 7.13 460 10.10 *

• peristaltic D-2 12/5/05 17 7.28 684 10.20 *

• peristaltic D-2 1/4/06 10.31 7 6.35 935 9.90

• clear peristaltic D-2 1/4/06 9 6.33 932 9.94

• clear peristaltic D-2 1/4/06 11 6.31 932 9.96

• clear peristaltic D-2D 1/4/06 9.76 10 6.87 1414 12.17

• clear peristaltic D-2D 1/4/06 13 6.71 1412 12.21

• clear peristaltic D-2D 1/4/06 16 6.62 1413 12.24

• clear peristaltic D-3 12/2/05 11.05 10 7.58 653 13.10

• cloudy peristaltic D-3 12/2/05 15 7.36 656 14.00

• slightly cloudy peristaltic D-3 12/2/05 20 7.36 659 14.10

• slightly cloudy peristaltic D-3 1/4/06 10.85 10 6.49 329 11.75

• slightly cloudy peristaltic D-3 1/4/06 13 6.38 399 11.70

• slightly cloudy peristaltic D-3 1/4/06 16 6.39 386 11.74

• clear peristaltic D-3D 12/23/05 10.71 10 7.22 756 13.16

• slightly cloudy peristaltic D-3D 12/23/05 12 7.13 772 13.23

• clear peristaltic D-3D 12/23/05 14 7.11 778 13.14

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 12 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 D-3D 1/4/06 10.60 10 6.73 728 12.62

• slightly cloudy peristaltic D-3D 1/4/06 13 6.69 802 12.68

• clear peristaltic D-3D 1/4/06 16 6.69 812 12.69

• clear peristaltic D-5 12/2/05 10.86 10 7.81 635 12.00

• cloudy peristaltic D-5 12/2/05 15 7.60 651 12.20

• cloudy peristaltic D-5 12/2/05 20 7.57 652 12.30

• cloudy peristaltic F-1 12/12/05 7.40 10 7.33 766 14.40

• cloudy peristaltic F-1 12/12/05 13 7.29 759 14.50

• slightly cloudy peristaltic F-1 12/12/05 16 7.30 763 14.30

• slightly cloudy peristaltic F-1 1/3/06 7.19 10 7.05 839 12.92

• slightly cloudy peristaltic F-1 1/3/06 13 7.28 837 12.98

• slightly cloudy peristaltic F-1 1/3/06 16 7.32 826 12.97

• clear peristaltic F-1D 12/12/05 7.35 10 8.07 594 14.80

• slightly cloudy peristaltic F-1D 12/12/05 13 7.80 592 14.50

• slightly cloudy peristaltic F-1D 12/12/05 16 7.59 589 14.30

• clear peristaltic F-1D 1/3/06 7.10 10 7.95 652 13.57

• slightly cloudy peristaltic F-1D 1/3/06 13 7.92 652 13.59

• clear peristaltic F-1D 1/3/06 16 7.87 651 13.60

• clear peristaltic F-2D 1/9/06 7.26 10 7.01 501 12.77

• clear peristaltic F-2D 1/9/06 13 6.98 501 12.70

• clear peristaltic F-2D 1/9/06 16 6.93 500 12.54

• clear peristaltic F-3D 1/9/06 8.57 10 7.57 357 14.65

• slightly cloudy peristaltic F-3D 1/9/06 12 7.60 347 14.22

• clear peristaltic F-3D 1/9/06 14 7.61 346 14.14

• clear peristaltic F-3D 1/12/06 8.67 10 7.42 289 12.80

• clear peristaltic F-3D 1/12/06 12 7.38 275 12.77

• clear peristaltic F-3D 1/12/06 14 7.35 278 12.85

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 13 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 F-4D 1/24/06 10.87 15 6.77 567 11.09

• cloudy peristaltic F-4D 1/24/06 18 6.70 569 10.91

• slightly cloudy peristaltic F-4D 1/24/06 21 6.71 570 10.98

• slightly cloudy peristaltic F-5D 1/24/06 6.65 10 7.41 619 12.00

• clear peristaltic F-5D 1/24/06 13 7.09 637 12.27

• clear peristaltic F-5D 1/24/06 16 6.95 626 12.26

• clear peristaltic F-6D 1/24/06 9.26 10 6.41 592 13.51

• cloudy peristaltic F-6D 1/24/06 13 6.86 589 13.68

• cloudy peristaltic F-6D 1/24/06 16 6.82 587 13.49

• slightly cloudy peristaltic F-7D 1/24/06 8.48 10 6.89 761 12.39

• clear peristaltic F-7D 1/24/06 12 6.88 813 12.21

• clear peristaltic F-7D 1/24/06 14 6.82 856 12.21

• clear peristaltic F-8D 1/24/06 9.70 10 7.14 557 13.12

• slightly cloudy peristaltic F-8D 1/24/06 13 6.48 554 13.03

• clear peristaltic F-8D 1/24/06 16 6.95 556 12.99

• clear peristaltic G-1 12/6/05 5.55 10 7.71 614 13.00

• cloudy peristaltic G-1 12/6/05 15 7.51 618 13.40

• slightly cloudy peristaltic G-1 12/6/05 20 7.36 624 12.80

• slightly cloudy peristaltic G-2 12/6/05 5.31 10 7.78 487 12.60

• slightly cloudy peristaltic G-2 12/6/05 15 7.78 481 13.10

• slightly cloudy peristaltic G-2 12/6/05 20 7.63 491 12.30

• slightly cloudy peristaltic G-2D 1/26/06 3.65 10 7.89 493 11.70 *

• peristaltic G-2D 1/26/06 15 7.86 502 10.90 *

• peristaltic G-2D 1/26/06 20 7.83 511 11.10 *

• peristaltic G-3 12/6/05 7.25 10 7.56 525 14.30

• slightly cloudy peristaltic G-3 12/6/05 15 7.63 495 13.90

• clear peristaltic G-3 12/6/05 20 7.35 490 13.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 14 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 MW-101 11/15/05 11.60 5 6.96 151 13.70 38.8 clear with suspended particles peristaltic MW-101 11/15/05 6 DRY MW-103 11/15/05 7.70 5 7.17 340 12.20 100 cloudy with suspended particles peristaltic MW-103 11/15/05 15 7.23 341 12.20 64.3 slightly cloudy with suspended particles peristaltic MW-103 11/15/05 20 7.19 340 12.60 21.2 clear with suspended particles peristaltic MW-103 11/15/05 25 7.22 341 12.20 13.1 clear peristaltic MW-105 11/15/05 9.30 5 7.06 554 15.30 117 cloudy peristaltic MW-105 11/15/05 10 7.15 475 15.50 63.2 slightly cloudy peristaltic MW-105 11/15/05 15 7.17 464 15.50 36.4 clear with suspended particles peristaltic MW-105 11/15/05 20 7.17 457 15.50 20.5 clear peristaltic MW-105 1/4/06 6.05 10 7.34 354 12.60 18.1 clear peristaltic MW-105 1/4/06 13 7.27 357 12.80 11.3 clear peristaltic MW-105 1/4/06 16 7.24 360 12.80 8.4 clear peristaltic MW-105D 12/16/05 6.81 10 8.18 378 14.20

• clear peristaltic MW-105D 12/16/05 13 8.02 382 14.50

• clear peristaltic MW-105D 12/16/05 16 7.92 382 14.30

• clear peristaltic MW-105D 1/4/06 6.48 10 7.17 366 13.80 22.6 clear peristaltic MW-105D 1/4/06 13 7.14 368 14.20 17.5 clear peristaltic MW-105D 1/4/06 16 7.14 368 14.30 15.2 clear peristaltic MW-106 11/14/05 10.82 10 8.14 323 13.70 7.17 clear peristaltic MW-106 11/14/05 15 7.87 316 14.60 7.74 clear peristaltic MW-106 11/14/05 20 7.73 318 14.70 8.95 clear peristaltic MW-106 11/14/05 25 7.73 323 14.60 5.17 clear peristaltic MW-106 1/4/06 10.42 10 7.27 317 10.40 16.7 clear peristaltic MW-106 1/4/06 13 7.27 309 10.30 12.2 clear peristaltic MW-106 1/4/06 16 7.25 309 10.40 9.8 clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 15 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 MW-106D 12/16/05 9.84 10 7.94 467 12.20

• clear peristaltic MW-106D 12/16/05 13 7.81 471 12.60

• clear peristaltic MW-106D 12/16/05 16 7.76 473 12.90

• clear peristaltic MW-106D 1/4/06 9.52 10 7.18 435 11.30 20.1 clear peristaltic MW-106D 1/4/06 13 7.14 438 11.60 16.8 clear peristaltic MW-106D 1/4/06 16 7.13 442 11.70 12.5 clear peristaltic MW-107 11/16/05 10.71 5.00 7.41 415 14.00 29.8 clear with suspended particles peristaltic MW-107 11/16/05 10.00 7.46 405 14.80 12.6 clear peristaltic MW-107 11/16/05 15.00 7.48 402 14.30 8.73 clear peristaltic MW-107 11/16/05 20.00 7.50 401 14.20 5.75 clear peristaltic MW-108 11/16/05 11.18 5.00 6.98 782 14.30 2.74 clear peristaltic MW-108 11/16/05 10.00 7.02 773 13.80 2.52 clear peristaltic MW-108 11/16/05 15.00 7.03 773 13.70 3.16 clear peristaltic MW-110 11/14/05 19.28 10 7.14 950 13.60 11 clear peristaltic MW-110 11/14/05 20 7.24 878 13.60 5.03 clear peristaltic MW-110 11/14/05 25 7.31 866 13.30 3.6 clear peristaltic MW-110 11/14/05 19.26 30 7.33 860 13.80 3.18 clear peristaltic MW-110 11/16/05 19.19 5.00 7.06 1024 13.20 6.05 clear peristaltic MW-110 11/16/05 10.00 7.09 1011 12.50 3.24 clear peristaltic MW-110 11/16/05 15.00 7.09 1008 12.50 2.53 clear peristaltic MW-110 11/16/05 20.00 7.12 1002 12.60 2.42 clear peristaltic MW-110 1/4/06 19.46 5 7.08 1105 11.27

• clear peristaltic MW-110 1/4/06 10 7.07 1105 11.23

• clear peristaltic MW-110 1/4/06 15 7.06 1105 11.22

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 16 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 MW-111 11/15/05 16.74 5 7.12 300 13.90 5.89 clear peristaltic MW-111 11/15/05 10 7.59 181 13.80 2.96 clear peristaltic MW-111 11/15/05 15 7.64 160 13.80 1.87 clear peristaltic MW-111 11/15/05 20 7.66 159 13.80 1.55 clear peristaltic MW-111 11/15/05 MW-111 1/4/06 16.55 10 7.30 118 11.80 11.3 clear peristaltic MW-111 1/4/06 13 7.33 116 12.20 9.5 clear peristaltic MW-111 1/4/06 16 7.33 116 12.20 7.8 clear peristaltic MW-111 1/4/06 MW-111D 1/9/06 14.35 10 7.69 345 15.36

• slightly cloudy peristaltic MW-111D 1/9/06 13 7.85 346 14.90

• slightly cloudy peristaltic MW-111D 1/9/06 16 7.88 345 14.83

• clear peristaltic MW-111D 1/9/06 MW-112 11/15/05 12.13 5 7.11 402 15.00 65.3 slightly cloudy peristaltic MW-112 11/15/05 10 7.15 386 15.10 28.7 clear peristaltic MW-112 11/15/05 15 7.16 384 15.10 20.5 clear peristaltic MW-112 11/15/05 MW-112 1/4/06 11.77 5 7.26 335 10.80 18.7 clear peristaltic MW-112 1/4/06 8 7.23 339 10.90 16.4 clear peristaltic MW-112 1/4/06 11 7.20 340 11.20 13.8 clear peristaltic MW-112 1/4/06 MW-112D 1/9/06 9.87 15 7.19 678 14.97

• cloudy peristaltic MW-112D 1/9/06 18 7.12 683 14.66

• slightly cloudy peristaltic MW-112D 1/9/06 21 7.06 686 14.41

• slightly cloudy peristaltic MW-112D 1/9/06 MW-113 11/15/05 8.75 5 6.95 615 12.60 17.5 clear peristaltic MW-113 11/15/05 10 6.96 586 12.60 10.4 clear peristaltic MW-113 11/15/05 15 6.95 568 12.80 7.53 clear peristaltic MW-113 11/15/05 20 6.95 571 12.80 4.76 clear peristaltic MW-113 11/15/05 CRA 016841 (12)

TABLE 4.3 Page 17 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 MW-113 12/5/05 8.89 5 7.14 484 11.70 *

• peristaltic MW-113 12/5/05 10 7.13 477 11.70 *

• peristaltic MW-113 12/5/05 15 7.13 483 11.50 *

• peristaltic MW-113 12/5/05 MW-113 1/3/06 8.97 15 7.52 556 10.90 35.2 clear peristaltic MW-113 1/3/06 18 7.48 509 11.20 24.1 clear peristaltic MW-113 1/3/06 21 7.45 509 11.50 19.2 clear peristaltic MW-113 1/3/06 24 7.44 505 11.40 17.8 clear peristaltic MW-113 1/3/06 MW-113D 12/14/05 6.12 10 7.90 432 12.70

• clear peristaltic MW-113D 12/14/05 13 7.90 431 12.10

• clear peristaltic MW-113D 12/14/05 16 7.77 429 12.20

• clear peristaltic MW-113D 12/14/05 MW-113D 1/3/06 6.13 10 7.40 422 12.20 51.7 cloudy peristaltic MW-113D 1/3/06 13 7.39 418 12.40 39.3 clear peristaltic MW-113D 1/3/06 16 7.38 418 12.40 26.7 clear peristaltic P-1 12/1/05 5.08 10 7.21 432 15.70

• cloudy, gray peristaltic P-1 12/1/05 15 7.46 427 16.40

• cloudy, gray peristaltic P-1 12/1/05 20 7.54 424 16.70

• cloudy, gray peristaltic P-1 12/1/05 P-2 12/2/05 5.95 15 8.47 478 15.60

• cloudy peristaltic P-2 12/2/05 20 8.56 363 17.50

• slightly cloudy peristaltic P-2 12/2/05 25 8.55 352 18.00

• slightly cloudy peristaltic P-2 1/3/06 5.81 10 8.41 391 15.65

• slightly cloudy peristaltic P-2 1/3/06 13 8.63 393 15.67

• slightly cloudy peristaltic P-2 1/3/06 16 8.75 395 15.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 18 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-2D 12/12/05 6.26 10 8.02 369 17.80

• slightly cloudy peristaltic P-2D 12/12/05 13 7.93 364 17.90

• clear peristaltic P-2D 12/12/05 16 7.89 381 16.90

• clear peristaltic P-2D 1/3/06 6.08 10 8.23 412 17.73

• slightly cloudy peristaltic P-2D 1/3/06 13 8.15 412 17.76

• clear peristaltic P-2D 1/3/06 16 8.07 412 17.78

• clear peristaltic P-3 12/2/05 6.08 10 7.25 742 16.40

• cloudy, dark peristaltic P-3 12/2/05 15 7.24 760 17.80

• cloudy peristaltic P-3 12/2/05 20 7.17 762 17.70

• cloudy peristaltic P-4 12/1/05 6.41 10 6.55 923 14.20

• slightly cloudy, gray peristaltic P-4 12/1/05 15 6.50 931 14.80

• slightly cloudy, gray peristaltic P-4 12/1/05 20 6.50 922 15.00

• clear peristaltic P-4 12/6/05 6.50 10 5.78 665 12.00 *

• peristaltic P-4 12/6/05 15 5.95 714 13.80 *

• peristaltic P-4 12/6/05 20 5.97 716 13.60 *

• peristaltic P-4 1/3/06 6.41 10 7.22 727 11.90

• clear peristaltic P-4 1/3/06 15 7.07 723 12.30

• clear peristaltic P-4 1/3/06 20 6.94 754 12.60

• clear peristaltic P-4 1/3/06 25 6.89 761 12.70

• clear peristaltic P-4 1/3/06 30 6.88 761 12.70

• clear peristaltic P-4 1/11/06 6.31 10 7.16 760 12.40

• clear peristaltic P-4 1/11/06 13 7.04 762 12.30

• clear peristaltic P-4 1/11/06 16 7.00 763 12.20

• clear peristaltic P-4 1/18/06 6.28 10 5.83 1043 10.29

• clear peristaltic P-4 1/18/06 13 5.75 1044 10.31

• clear peristaltic P-4 1/18/06 16 5.69 1047 10.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 19 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-4 1/25/06 6.21 10 7.37 753 9.20 195 slightly cloudy peristaltic P-4 1/25/06 15 7.04 775 9.30 122 clear peristaltic P-4 1/25/06 20 7.06 769 10.00 78.3 clear peristaltic P-4 1/25/06 25 7.00 772 9.80 56.4 clear peristaltic P-4 2/1/06 5.95 10 6.99 674 12.20

• clear peristaltic P-4 2/1/06 13 6.66 682 12.40

• clear peristaltic P-4 2/1/06 16 6.46 683 12.40

• clear peristaltic P-4 2/9/06 5.98 5 5.49 1131 10.11

• clear with yellow tint peristaltic P-4 2/9/06 10 5.43 1130 10.15

• clear with yellow tint peristaltic P-4 2/9/06 15 5.38 1132 10.16

• clear with yellow tint peristaltic P-4 2/15/06 6.00 10 7.14 748 11.20

• clear, yellow tint peristaltic P-4 2/15/06 13 6.90 747 11.40

• clear, yellow tint peristaltic P-4 2/15/06 16 6.75 752 11.40

• clear, yellow tint peristaltic P-4 2/22/06 6.06 10 7.24 1043 9.50

• clear peristaltic P-4 2/22/06 13 6.88 1064 10.00

• clear peristaltic P-4 2/22/06 16 6.80 1068 1.00

• clear peristaltic P-4 2/22/06 19 6.72 1079 10.10

• clear peristaltic P-4 3/1/06 5.95 10 7.57 793 11.40

• clear, yellow tint peristaltic P-4 3/1/06 13 7.49 802 10.60

• clear, yellow tint peristaltic P-4 3/1/06 16 7.45 796 10.80

• clear, yellow tint peristaltic P-4 3/7/06 6.00 10 7.22 762 10.50

• clear, yellow tint peristaltic P-4 3/7/06 13 6.86 760 10.70

• clear, yellow tint peristaltic P-4 3/7/06 16 6.83 760 10.70

• clear, yellow tint peristaltic P-4D 12/23/05 8.68 10 7.93 671 12.80

• cloudy peristaltic P-4D 12/23/05 13 7.86 673 13.20

• slightly cloudy peristaltic P-4D 12/23/05 16 7.82 681 13.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 20 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-4D 1/3/06 8.63 12 7.70 691 13.00

• slightly cloudy peristaltic P-4D 1/3/06 17 7.69 691 13.00

• slightly cloudy peristaltic P-4D 1/3/06 22 7.69 688 13.00

• clear peristaltic P-4D 1/11/06 8.55 10 7.67 672 12.90

• slightly cloudy peristaltic P-4D 1/11/06 13 7.71 672 12.70

• slightly cloudy peristaltic P-4D 1/11/06 16 7.72 670 12.70

• clear peristaltic P-4D 1/18/06 8.50 10 6.48 947 11.40

• clear peristaltic P-4D 1/18/06 13 6.48 945 11.57

• clear peristaltic P-4D 1/18/06 16 6.48 943 11.60

• clear peristaltic P-4D 1/25/06 8.48 10 7.94 336 9.90

• cloudy peristaltic P-4D 1/25/06 15 7.86 264 10.10

• slightly cloudy peristaltic P-4D 1/25/06 20 7.84 208 10.00

• slightly cloudy peristaltic P-4D 2/1/06 8.06 10 7.28 551 13.30

• clear peristaltic P-4D 2/1/06 13 7.20 539 13.70

• clear peristaltic P-4D 2/1/06 16 7.16 536 13.80

• clear peristaltic P-4D 2/9/06 8.20 5 6.45 789 11.60

• cloudy peristaltic P-4D 2/9/06 10 6.27 789 11.81

• slightly cloudy peristaltic P-4D 2/9/06 15 6.24 788 11.68

• clear peristaltic P-4D 2/15/06 8.28 10 7.31 562 11.90

• clear peristaltic P-4D 2/15/06 13 7.26 561 12.20

• clear peristaltic P-4D 2/15/06 16 7.22 564 12.30

• clear peristaltic P-4D 2/22/06 8.16 10 6.85 821 11.30

• cloudy peristaltic P-4D 2/22/06 13 7.25 794 11.90

• cloudy peristaltic P-4D 2/22/06 16 7.29 782 11.80

• cloudy peristaltic P-4D 2/22/06 19 7.30 784 12.10

• cloudy peristaltic CRA 016841 (12)

TABLE 4.3 Page 21 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-4D 3/1/06 8.19 12 7.98 648 12.90

• clear peristaltic P-4D 3/1/06 15 7.92 643 12.90

• clear peristaltic P-4D 3/1/06 18 7.82 641 12.90

• clear peristaltic P-4D 3/7/06 8.23 15 7.18 605 12.90

• clear peristaltic P-4D 3/7/06 18 7.19 603 13.00

• clear peristaltic P-4D 3/7/06 21 7.20 602 13.00

• clear peristaltic P-5 12/1/05 6.48 10 6.79 845 14.30

• clear peristaltic P-5 12/1/05 15 6.67 800 14.90

• clear peristaltic P-5 12/1/05 22 6.65 804 15.40

• clear peristaltic P-5 1/3/06 6.45 10 7.38 675 12.60

• clear peristaltic P-5 1/3/06 15 6.96 679 13.20

• clear peristaltic P-5 1/3/06 20 6.95 686 13.20

• clear peristaltic P-5 1/3/06 25 6.94 686 13.20

• clear peristaltic P-5D 12/23/05 10.22 10 7.65 453 12.86

• clear peristaltic P-5D 12/23/05 12 7.22 457 13.11

• clear peristaltic P-5D 12/23/05 14 7.15 458 13.13

• clear peristaltic P-5D 1/3/06 8.91 15 7.71 514 13.60

• clear peristaltic P-5D 1/3/06 20 7.71 515 13.60

• clear peristaltic P-5D 1/3/06 25 7.70 520 13.60

• clear peristaltic P-6 12/1/05 7.30 10 7.15 655 13.70

• cloudy, gray peristaltic P-6 12/1/05 15 7.13 659 13.90

• slightly cloudy, gray peristaltic P-6 12/1/05 20 7.11 669 14.30

• slightly cloudy, gray peristaltic P-6 1/18/06 6.18 10 6.37 234 9.97

• clear peristaltic P-6 1/18/06 12 6.20 237 10.34

• clear peristaltic P-6 1/18/06 14 6.10 235 10.33

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 22 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-7 12/1/05 9.58 10 6.80 1257 13.70

• cloudy, gray peristaltic P-7 12/1/05 15 6.71 1272 13.90

• slightly cloudy, gray peristaltic P-7 12/1/05 20 6.74 1268 14.20

• slightly cloudy, gray peristaltic P-8 12/1/05 5.63 10 6.90 644 13.90

• slightly cloudy, gray peristaltic P-8 12/1/05 15 6.96 627 14.90

• slightly cloudy, gray peristaltic P-8 12/1/05 20 6.95 623 14.60

• slightly cloudy, gray peristaltic P-8 12/6/05 5.74 10 6.43 498 14.00 *

• peristaltic P-8 12/6/05 15 6.45 503 14.60 *

• peristaltic P-8 12/6/05 20 6.43 518 14.40 *

• peristaltic P-9 12/5/05 8.75 10 7.07 229 12.70

• slightly cloudy peristaltic P-9 12/5/05 15 6.68 229 12.10

• clear peristaltic P-9 12/5/05 20 6.64 227 12.30

• clear peristaltic P-9 12/13/05

• 10 7.04 221 13.40

• clear peristaltic P-9 12/13/05 13 6.75 220 13.30

• clear peristaltic P-9 12/13/05 16 6.51 223 12.90

• clear peristaltic P-10 12/5/05 6.54 10 8.04 466 13.90

• cloudy peristaltic P-10 12/5/05 15 8.07 451 14.10

• clear peristaltic P-10 12/5/05 20 7.96 458 13.70

• clear peristaltic P-11 12/5/05 6.55 10 7.90 645 12.60

• cloudy peristaltic P-11 12/5/05 15 7.84 640 14.10

• clear peristaltic P-11 12/5/05 20 7.74 637 13.90

• clear peristaltic P-11 12/5/05 P-12 12/5/05 6.79 10 7.90 554 12.60

• slightly cloudy peristaltic P-12 12/5/05 15 7.66 557 14.30

• clear peristaltic P-12 12/5/05 20 7.49 569 13.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 23 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-13D 12/23/05 8.34 10 8.09 812 14.10

• slightly cloudy peristaltic P-13D 12/23/05 13 7.89 809 13.90

• clear peristaltic P-13D 12/23/05 16 7.82 809 13.90

• clear peristaltic P-13D 1/3/06 8.25 10 7.70 825 14.00

• clear peristaltic P-13D 1/3/06 15 7.68 827 14.00

• clear peristaltic P-13D 1/3/06 20 7.67 827 14.00

• clear peristaltic P-13D 1/11/06 5.26 10 7.81 863 13.50

• clear peristaltic P-13D 1/11/06 13 7.72 821 13.60

• clear peristaltic P-13D 1/11/06 16 7.71 818 13.70

• clear peristaltic P-13D 1/18/06 5.20 17 6.56 1114 9.61

• clear peristaltic P-13D 1/18/06 20 6.40 1113 11.63

• clear peristaltic P-13D 1/18/06 23 6.45 1113 11.67

• clear peristaltic P-13D 1/25/06 8.16 10 7.47 790 11.70 132 slightly cloudy peristaltic P-13D 1/25/06 15 7.68 789 11.20 82.1 clear peristaltic P-13D 1/25/06 20 7.71 788 10.90 57.2 clear peristaltic P-13D 1/25/06 25 7.70 786 11.00 42.5 clear peristaltic P-13D 2/1/06 7.90 10 7.39 775 13.70

• clear peristaltic P-13D 2/1/06 13 7.20 692 14.30

• clear peristaltic P-13D 2/1/06 16 7.12 689 14.40

• clear peristaltic P-13D 2/9/06 7.98 5 6.21 1045 11.69

• clear peristaltic P-13D 2/9/06 10 6.07 1043 11.77

• clear peristaltic P-13D 2/9/06 15 6.04 1043 11.60

• clear peristaltic P-13D 2/15/06 7.99 10 7.45 664 13.00

• clear peristaltic P-13D 2/15/06 13 7.34 664 13.20

• clear peristaltic P-13D 2/15/06 16 7.26 667 13.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 24 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-13D 2/22/06 8.02 10 7.54 915 10.00

• slightly cloudy peristaltic P-13D 2/22/06 13 7.57 905 10.50

• clear peristaltic P-13D 2/22/06 16 7.46 919 10.70

• clear peristaltic P-13D 3/1/06 7.90 12 8.81 768 13.20

• clear peristaltic P-13D 3/1/06 15 8.36 769 12.50

• clear peristaltic P-13D 3/1/06 18 8.27 763 12.80

• clear peristaltic P-13D 3/7/06 7.93 10 7.90 770 13.00

• clear peristaltic P-13D 3/7/06 13 7.61 715 13.40

• clear peristaltic P-13D 3/7/06 16 7.46 708 13.10

• clear peristaltic P-13D 3/7/06 19 7.44 705 13.10

• clear peristaltic P-14 1/24/06 6.40 10 6.76 514 12.26

• clear peristaltic P-14 1/24/06 13 6.70 515 12.41

• clear peristaltic P-14 1/24/06 16 6.69 515 12.26

• clear peristaltic P-14D 1/24/06 7.89 10 7.02 509 14.48

• clear peristaltic P-14D 1/24/06 13 6.86 512 14.46

• clear peristaltic P-14D 1/24/06 16 6.79 511 14.36

• clear peristaltic S-1 12/5/05 7.50 10 7.52 377 13.10

• slightly cloudy peristaltic S-1 12/5/05 15 7.86 380 13.50

• clear peristaltic S-1 12/5/05 20 8.01 383 13.80

• clear peristaltic S-1D 1/26/06 7.87 10 8.54 306 13.80 537 cloudy peristaltic S-1D 1/26/06 15 8.45 304 13.50 521 cloudy peristaltic S-1D 1/26/06 20 8.39 307 13.20 507 cloudy peristaltic S-1D 1/26/06 25 8.36 306 13.00 503 cloudy peristaltic S-2 12/5/05 5.22 10 7.81 546 12.50

• slightly cloudy peristaltic S-2 12/5/05 15 7.62 553 12.50

• clear peristaltic S-2 12/5/05 20 7.68 553 12.50

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 25 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 S-2 1/3/06 4.68 10 7.27 630 12.15

• clear peristaltic S-2 1/3/06 13 7.25 629 12.18

• clear peristaltic S-2 1/3/06 16 7.10 628 12.20

• clear peristaltic S-2 2/1/06 3.80 10 7.10 496 12.20

• clear peristaltic S-2 2/1/06 13 7.03 497 12.20

• clear peristaltic S-2 2/1/06 16 7.01 495 12.30

• clear peristaltic S-2 2/9/06 3.98 5 10.37 689 10.37

• clear peristaltic S-2 2/9/06 10 10.36 688 10.36

• clear peristaltic S-2 2/9/06 15 10.37 688 10.37

• clear peristaltic S-2 2/15/06 4.04 10 7.09 483 11.60

• clear peristaltic S-2 2/15/06 13 7.08 483 11.60

• clear peristaltic S-2 2/15/06 16 7.07 482 11.70

• clear peristaltic S-2 2/22/06 4.08 10 7.49 649 10.20

• cloudy peristaltic S-2 2/22/06 13 7.42 642 10.20

• clear peristaltic S-2 2/22/06 16 7.43 630 10.40

• clear peristaltic S-2 3/1/06 3.91 10 7.35 532 10.60

• clear peristaltic S-2 3/1/06 13 7.34 537 10.60

• clear peristaltic S-2 3/1/06 16 7.34 535 10.70

• clear peristaltic S-2D 12/12/05 6.14 10 7.98 403 12.90

• slightly cloudy peristaltic S-2D 12/12/05 13 7.87 388 13.40

• slightly cloudy peristaltic S-2D 12/12/05 16 7.86 389 13.10

• slightly cloudy peristaltic S-2D 1/3/06 5.30 10 6.90 406 12.90

• slightly cloudy peristaltic S-2D 1/3/06 13 7.08 406 12.94

• clear peristaltic S-2D 1/3/06 16 6.98 407 12.96

• clear peristaltic S-2D 2/1/06 4.37 10 7.10 326 13.70

• clear peristaltic S-2D 2/1/06 13 7.10 325 13.80

• clear peristaltic S-2D 2/1/06 16 7.11 326 13.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 26 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 S-2D 2/9/06 4.56 5 6.11 427 11.88

• clear peristaltic S-2D 2/9/06 10 6.13 428 11.87

• clear peristaltic S-2D 2/9/06 15 6.13 428 11.98

• clear peristaltic S-2D 2/15/06 4.62 10 7.24 317 13.00

• clear peristaltic S-2D 2/15/06 13 7.20 318 13.20

• clear peristaltic S-2D 2/15/06 16 7.19 318 13.20

• clear peristaltic S-2D 2/22/06 4.65 10 7.62 397 11.70

• cloudy peristaltic S-2D 2/22/06 13 7.58 393 11.70

• cloudy peristaltic S-2D 2/22/06 16 7.57 398 11.80

• cloudy peristaltic S-2D 3/1/06 4.50 10 8.01 383 12.90

• clear peristaltic S-2D 3/1/06 13 8.10 362 12.00

• clear peristaltic S-2D 3/1/06 16 7.87 365 12.00

• clear peristaltic S-3 12/5/05 5.29 10 7.90 450 12.90

• clear peristaltic S-3 12/5/05 15 7.80 447 13.30

• clear peristaltic S-3 12/5/05 20 7.65 447 13.30

• clear peristaltic S-4 12/5/05 5.69 10 7.98 597 11.80

• cloudy peristaltic S-4 12/5/05 15 7.86 599 12.40

• cloudy peristaltic S-4 12/5/05 20 7.76 598 12.20

• clear peristaltic S-4D 1/26/06 7.75 10 8.10 419 12.80 63.8 slightly cloudy peristaltic S-4D 1/26/06 15 8.05 402 12.50 48.7 clear peristaltic S-4D 1/26/06 20 8.00 403 12.40 32.4 clear peristaltic S-5 12/5/05 4.25 10 8.20 392 11.10

• slightly cloudy peristaltic S-5 12/5/05 15 8.14 377 12.10

• slightly cloudy peristaltic S-5 12/5/05 20 8.07 389 12.20

• slightly cloudy peristaltic S-6 12/5/05 6.72 10 7.90 449 11.70

• slightly cloudy peristaltic S-6 12/5/05 15 7.79 454 12.40

• clear peristaltic S-6 12/5/05 20 7.75 452 12.10

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 27 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 S-7 1/24/06 4.98 10 6.64 693 9.28

• clear peristaltic S-7 1/24/06 13 6.62 698 9.26

• clear peristaltic S-7 1/24/06 16 6.61 698 9.21

• clear peristaltic S-7D 1/24/06 6.80 10 7.71 469 10.87

• clear peristaltic S-7D 1/24/06 13 7.19 471 11.05

• clear peristaltic S-7D 1/24/06 16 7.12 473 10.70

• clear peristaltic VB-1-1 11/16/05 13.30 10 7.77 1061 17.72

• clear peristaltic VB-1-1 11/16/05 12 7.68 1057 17.62

• clear peristaltic VB-1-1 11/16/05 14 7.63 1054 17.74

• clear peristaltic VB-1-1 1/4/06 13.00 5 8.06 835 13.30 *

• peristaltic VB-1-1 1/4/06 10 8.05 831 13.20 *

• peristaltic VB-1-1 1/4/06 15 8.02 827 13.40 845

• peristaltic VB-1-1D 12/16/05 12.34 13 7.47 545 13.77

• clear peristaltic VB-1-1D 12/16/05 16 7.55 554 14.20

• clear peristaltic VB-1-1D 12/16/05 19 7.56 559 14.24

• clear peristaltic VB-1-1D 1/4/06 12.30 10 7.02 644 13.62

• slightly cloudy peristaltic VB-1-1D 1/4/06 13 7.01 644 13.85

• slightly cloudy peristaltic VB-1-1D 1/4/06 16 7.00 645 13.87

• clear peristaltic VB-1-2D 1/13/06 9.40 10 7.16 636 12.72

• slightly cloudy peristaltic VB-1-2D 1/13/06 13 7.18 643 12.80

• clear peristaltic VB-1-2D 1/13/06 16 7.14 651 12.83

• clear peristaltic VB-1-3 11/16/05 11.97 10 7.33 313 13.24

• clear peristaltic VB-1-3 11/16/05 12 7.24 311 13.40

• clear peristaltic VB-1-3 11/16/05 14 7.27 312 13.43

• clear peristaltic VB-1-3D 1/13/06 9.65 10 7.20 661 12.65

• clear peristaltic VB-1-3D 1/13/06 12 7.21 654 12.60

• clear peristaltic VB-1-3D 1/13/06 15 7.21 660 12.59

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 28 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-1-4 11/16/05 10.62 10 7.44 458 13.40

• clear peristaltic VB-1-4 11/16/05 12 7.42 456 13.42

• clear peristaltic VB-1-4 11/16/05 14 7.42 454 13.22

• clear peristaltic VB-1-4D 1/13/06 8.90 25 7.07 924 10.40

• slightly cloudy peristaltic VB-1-4D 1/13/06 30 7.01 929 10.71

• clear peristaltic VB-1-4D 1/13/06 35 7.10 931 10.92

• clear peristaltic VB-1-5 11/16/05 12.52 10 6.96 770 13.52

• clear peristaltic VB-1-5 11/16/05 12 6.92 765 13.15

• clear peristaltic VB-1-5 11/16/05 14 6.92 769 13.14

• clear peristaltic VB-1-5D 1/13/06 10.29 10 8.02 562 13.20

• slightly cloudy peristaltic VB-1-5D 1/13/06 13 7.95 558 13.20

• slightly cloudy peristaltic VB-1-5D 1/13/06 16 7.92 562 13.20

• clear peristaltic VB-1-6 11/22/05 14.38 10 7.97 191 13.88

• slightly cloudy peristaltic VB-1-6 11/22/05 13 8.05 175 13.69

• clear peristaltic VB-1-6 11/22/05 16 8.07 172 13.54

• clear peristaltic VB-1-6D 1/13/06 14.30 10 8.49 271 13.80

• clear peristaltic VB-1-6D 1/13/06 13 8.49 268 13.10

• clear peristaltic VB-1-6D 1/13/06 16 8.40 267 13.10

• clear peristaltic VB-1-7 11/22/05 12.44 10 8.16 267 14.01

• slightly cloudy peristaltic VB-1-7 11/22/05 13 8.04 264 13.99

• slightly cloudy peristaltic VB-1-7 11/22/05 16 7.97 264 13.71

• clear peristaltic VB-1-7D 1/9/06 11.00 10 7.32 658 14.50

• slightly cloudy peristaltic VB-1-7D 1/9/06 13 7.19 702 14.77

• slightly cloudy peristaltic VB-1-7D 1/9/06 16 7.14 719 13.98

• clear peristaltic VB-1-8 11/22/05 12.15 10 7.05 731 12.72

• cloudy peristaltic VB-1-8 11/22/05 13 7.19 739 12.86

• cloudy peristaltic VB-1-8 11/22/05 16 7.09 744 12.84

• slightly cloudy peristaltic CRA 016841 (12)

TABLE 4.3 Page 29 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-1-8D 1/9/06 10.52 10 7.13 788 14.36

• slightly cloudy peristaltic VB-1-8D 1/9/06 13 7.07 803 14.76

• clear peristaltic VB-1-8D 1/9/06 16 7.01 801 14.05

• clear peristaltic VB-1-9 11/22/05 10.76 10 7.13 582 12.06

• cloudy peristaltic VB-1-9 11/22/05 13 7.18 572 12.37

• clear peristaltic VB-1-9 11/22/05 16 7.12 566 12.46

• clear peristaltic VB-1-9D 1/13/06 10.91 10 7.42 423 11.20

• clear peristaltic VB-1-9D 1/13/06 13 7.42 440 11.35

• clear peristaltic VB-1-9D 1/13/06 16 7.39 442 11.30

• clear peristaltic VB-2-1 11/15/05 14.87 10 7.94 146 13.90

• slightly cloudy peristaltic VB-2-1 11/15/05 12 8.49 142 14.13

• clear peristaltic VB-2-1 11/15/05 14 8.51 140 14.11

• clear peristaltic VB-2-2 11/15/05 8.80 10 7.32 593 14.07

• clear peristaltic VB-2-2 11/15/05 12 7.28 593 13.83

• clear peristaltic VB-2-2 11/15/05 14 7.27 593 13.79

• clear peristaltic VB-2-2 12/5/05 8.89 10 7.24 472 11.60 *

• peristaltic VB-2-2 12/5/05 15 7.31 480 11.70 *

• peristaltic VB-2-2 12/5/05 20 7.32 488 11.90 *

• peristaltic VB-2-2 1/4/06 8.60 15 7.47 468 10.60 17.2 clear peristaltic VB-2-2 1/4/06 18 7.38 476 10.70 12.8 clear peristaltic VB-2-2 1/4/06 21 7.32 473 10.60 9.5 clear peristaltic VB-2-2 1/4/06 24 7.28 477 10.70 8.6 clear peristaltic VB-2-2D 12/23/05 8.00 10 7.41 429 11.33

• clear peristaltic VB-2-2D 12/23/05 12 7.37 430 11.33

• clear peristaltic VB-2-2D 12/23/05 14 7.40 431 11.33

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 30 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-2-2D 1/4/06 7.83 5 7.21 355 11.50 42.8 cloudy peristaltic VB-2-2D 1/4/06 8 7.20 357 11.60 36.4 cloudy peristaltic VB-2-2D 1/4/06 11 7.19 353 11.80 29.1 cloudy peristaltic VB-2-3 11/15/05 9.03 10 6.80 574 13.22

• clear peristaltic VB-2-3 11/15/05 12 6.82 572 13.23

• clear peristaltic VB-2-3 11/15/05 14 6.83 569 13.23

• clear peristaltic VB-2-4 11/15/05 10.00 10 7.61 455 13.42

• slightly cloudy peristaltic VB-2-4 11/15/05 12 7.57 458 13.45

• slightly cloudy peristaltic VB-2-4 11/15/05 14 7.50 456 13.16

• clear peristaltic VB-2-5 11/15/05 9.20 10 6.65 585 12.99

• clear peristaltic VB-2-5 11/15/05 12 6.66 585 13.27

• clear peristaltic VB-2-5 11/15/05 14 6.65 584 13.28

• clear peristaltic VB-2-5 1/3/06 9.30 10 6.44 657 9.09

• clear peristaltic VB-2-5 1/3/06 12 6.42 656 9.10

• clear peristaltic VB-2-5 1/3/06 14 6.42 657 9.06

• clear peristaltic VB-2-5D 12/14/05 6.02 27 7.29 443 11.00

• clear peristaltic VB-2-5D 12/14/05 30 7.27 444 10.75

• clear peristaltic VB-2-5D 12/14/05 33 7.27 444 10.49

• clear peristaltic VB-2-5D 1/3/06 6.61 10 6.70 495 11.80

• clear peristaltic VB-2-5D 1/3/06 12 6.72 495 11.81

• clear peristaltic VB-2-5D 1/3/06 14 6.76 497 11.81

• clear peristaltic VB-2-6 11/15/05 10.80 10 6.42 472 13.67

• clear peristaltic VB-2-6 11/15/05 12 6.17 470 13.66

• clear peristaltic VB-2-6 11/15/05 14 6.14 470 13.65

• clear peristaltic VB-2-6 12/5/05 10.93 10 6.50 430 12.20 *

• peristaltic VB-2-6 12/5/05 15 6.48 430 11.90 *

• peristaltic VB-2-6 12/5/05 20 6.51 420 12.10 *

• peristaltic CRA 016841 (12)

TABLE 4.3 Page 31 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-2-6 1/3/06 7.94 5 7.47 433 11.10 48.4 cloudy peristaltic VB-2-6 1/3/06 8 7.10 279 11.10 39.8 clear peristaltic VB-2-6 1/3/06 11 6.91 416 11.10 26.2 clear peristaltic VB-2-6 1/3/06 14 7.18 426 11.20 20.9 clear peristaltic VB-2-6 1/3/06 17 7.14 420 11.10 18.5 clear peristaltic VB-2-6 1/3/06 20 7.11 408 11.20 16.7 clear peristaltic VB-2-6D 12/14/05 6.12 30 7.62 263 11.43

• slightly cloudy peristaltic VB-2-6D 12/14/05 33 7.61 265 11.65

• slightly cloudy peristaltic VB-2-6D 12/14/05 36 7.63 264 11.65

• clear peristaltic VB-2-6D 1/3/06 6.11 5 6.92 252 12.30 33.8 clear peristaltic VB-2-6D 1/3/06 8 7.02 242 12.40 27.4 clear peristaltic VB-2-6D 1/3/06 11 7.11 244 12.70 23.6 clear peristaltic VB-2-6D 1/3/06 14 7.12 238 12.80 20.1 clear peristaltic VB-2-7 12/14/05 11.19 2 8.55 170 12.65

• clear peristaltic VB-2-7 12/14/05 5 8.20 175 12.70

• clear peristaltic VB-2-7 12/14/05 8 8.20 175 12.63

• clear peristaltic VB-2-7 1/4/06 10.99 15 7.36 144 12.40 13.6 clear peristaltic VB-2-7 1/4/06 18 7.41 139 12.70 10.8 clear peristaltic VB-2-7 1/4/06 21 7.41 142 12.80 8.2 clear peristaltic VB-2-7D 12/14/05 11.39 33 8.09 212 12.18

• clear peristaltic VB-2-7D 12/14/05 36 8.01 211 12.21

• clear peristaltic VB-2-7D 12/14/05 39 7.95 214 12.34

• clear peristaltic VB-2-7D 1/4/06 11.26 5 7.43 148 13.00 29.3 clear peristaltic VB-2-7D 1/4/06 8 7.41 149 13.30 22.7 clear peristaltic VB-2-7D 1/4/06 11 7.40 149 13.20 16.9 clear peristaltic VB-2-8 12/14/05 8.27 12 7.95 262 13.41

• clear peristaltic VB-2-8 12/14/05 15 7.82 262 12.69

• clear peristaltic VB-2-8 12/14/05 18 7.85 262 12.42

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 32 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-2-9 1/12/06 8.49 10 6.70 501 13.01

• slightly cloudy peristaltic VB-2-9 1/12/06 13 6.39 509 12.93

• slightly cloudy peristaltic VB-2-9 1/12/06 16 6.22 509 12.31

• clear peristaltic VB-2-9D 1/12/06 9.69 10 7.17 313 14.10

• cloudy peristaltic VB-2-9D 1/12/06 13 7.18 313 14.07

• cloudy peristaltic VB-2-9D 1/12/06 16 7.16 310 14.07

• cloudy peristaltic VB-3-1 11/15/05 9.83 10 7.29 608 14.10

• clear peristaltic VB-3-1 11/15/05 12 7.24 607 14.02

• clear peristaltic VB-3-1 11/15/05 14.00 7.23 608 14.01

• clear peristaltic VB-3-2 11/15/05 10.22 10 7.04 1002 14.69

• clear peristaltic VB-3-2 11/15/05 12 7.02 997 14.66

• clear peristaltic VB-3-2 11/15/05 14 6.99 994 14.68

• clear peristaltic VB-3-3 11/16/05 9.05 10 6.44 951 12.43

• clear peristaltic VB-3-3 11/16/05 12 6.39 949 12.54

• clear peristaltic VB-3-3 11/16/05 14 6.30 936 12.45

• clear peristaltic VB-3-4 11/16/05 10.58 10 5.94 907 12.13

• clear peristaltic VB-3-4 11/16/05 12 5.84 900 12.13

• clear peristaltic VB-3-4 11/16/05 14 5.80 898 12.16

• clear peristaltic VB-3-4 11/16/05 VB-3-4 11/16/05 VB-3-4 12/5/05 10.43 10 6.34 680 9.50 *

• peristaltic VB-3-4 12/5/05 15 6.36 670 9.70 *

• peristaltic VB-3-4 12/5/05 20 6.29 684 9.80 *

• peristaltic VB-3-4 1/3/06 10.33 10 5.96 875 8.51

• clear peristaltic VB-3-4 1/3/06 13 5.82 880 8.47

• clear peristaltic VB-3-4 1/3/06 16 5.73 886 8.49

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 33 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-3-4D 12/14/05 9.79 40 7.62 333 12.03

• clear peristaltic VB-3-4D 12/14/05 43 7.60 334 11.97

• clear peristaltic VB-3-4D 12/14/05 47 7.60 334 11.97

• clear peristaltic VB-3-4D 1/3/06 9.57 10 7.05 357 11.82

• clear peristaltic VB-3-4D 1/3/06 13 7.06 358 11.87

• clear peristaltic VB-3-4D 1/3/06 16 7.05 358 11.79

• clear peristaltic VB-3-5 11/22/05 9.44 10 7.28 272 13.43

• cloudy peristaltic VB-3-5 11/22/05 13 7.27 146 13.72

• cloudy peristaltic VB-3-5 11/22/05 16 7.33 261 13.73

• slightly cloudy peristaltic VB-3-6 11/22/05 8.60 10 7.24 757 12.38

• cloudy peristaltic VB-3-6 11/22/05 13 7.12 777 12.75

• slightly cloudy peristaltic VB-3-6 11/22/05 16 6.93 779 12.79

• clear peristaltic VB-3-7 12/2/05 8.19 10 7.66 203 11.30

• cloudy peristaltic VB-3-7 12/2/05 15 7.09 195 11.40

• cloudy peristaltic VB-3-7 12/2/05 20 6.94 194 11.50

• cloudy peristaltic VB-3-7 12/14/05 5.72 15 7.74 232 11.72

• clear peristaltic VB-3-7 12/14/05 18 7.71 231 11.66

• slightly cloudy peristaltic VB-3-7 12/14/05 21 7.68 231 11.62

• slightly cloudy peristaltic VB-3-7 1/3/06 7.91 10 6.76 243 9.27

• clear peristaltic VB-3-7 1/3/06 13 6.25 242 9.10

• clear peristaltic VB-3-7 1/3/06 16 6.12 241 9.09

• clear peristaltic VB-3-7D 1/3/06 5.45 10 7.34 252 11.56

• clear peristaltic VB-3-7D 1/3/06 13 7.27 251 11.58

• clear peristaltic VB-3-7D 1/3/06 16 7.23 250 11.60

• clear peristaltic VB-3-8 12/2/05 8.20 10 8.09 313 11.80

• cloudy peristaltic VB-3-8 12/2/05 15 8.15 318 11.10

• cloudy peristaltic VB-3-8 12/2/05 20 8.15 304 12.30

• cloudy peristaltic CRA 016841 (12)

TABLE 4.3 Page 34 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-3-9D 12/13/05 6.37 35 7.64 700 10.70

• cloudy peristaltic VB-3-9D 12/13/05 38 7.50 710 10.30

• cloudy peristaltic VB-3-9D 12/13/05 41 7.39 726 10.36

• cloudy peristaltic VB-3-9D 1/4/06 5.64 10 7.27 550 11.90 36.2 cloudy peristaltic VB-3-9D 1/4/06 13 7.22 549 12.20 28.4 cloudy peristaltic VB-3-9D 1/4/06 16 7.17 550 12.40 21.5 cloudy peristaltic VB-3-10 12/16/05 8.22 15 7.42 258 10.03

• cloudy peristaltic VB-3-10 12/16/05 20 7.39 154 10.10

• cloudy peristaltic VB-3-10 12/16/05 24 7.25 172 9.37

• cloudy peristaltic VB-3-10 1/3/06 7.88 15 7.17 683 10.90 24.4 clear peristaltic VB-3-10 1/3/06 18 7.18 684 11.00 20.7 clear peristaltic VB-3-10 1/3/06 21 7.16 686 11.00 17.2 clear peristaltic VB-3-10D 12/16/05 7.28 20 7.35 579 10.51

• clear peristaltic VB-3-10D 12/16/05 23 7.37 585 10.83

• clear peristaltic VB-3-10D 12/16/05 25 7.32 574 *

• clear peristaltic VB-3-10D 1/3/06 7.07 10 7.19 540 12.40 57.1 cloudy peristaltic VB-3-10D 1/3/06 13 7.18 543 12.50 42.3 cloudy peristaltic VB-3-10D 1/3/06 16 7.18 542 12.30 28.9 clear peristaltic 1

ft BTOC - feet below top of casing 2

mS/cm - millisiemens per centimeter 3

NTU - nephelometric turbidity units 4

• - Not measured CRA 016841 (12)

TABLE 4.4

SUMMARY

OF PRIVATE WATER WELLS DOWNGRADIENT OF THE SITE EXELON GENERATION BRAIDWOOD STATION Location Name / Elev Rate Record Number Total Depth Address Driller Drill Date Record Type Use Well Type Aquifer Type Stat LVL Pump LVL Status (Ft) Elev Ref Formation Top Bottom (gpm)

REC-222 14 281 Carol Lane, Braidwood owner 01/24/1992 Construction Report Domestic Driven Unconsolidated 9 14 WATER 0 - gravel 10 14 0 REC-237 14 270 Carol Lane owner 4/6/1992 Construction Report Domestic Driven Unconsolidated - - WATER 0 - 4 sand point 10 14 0 REC-191 19 300 Francis, Braidwood owner 11/27/1991 Construction Report Domestic Driven Unconsolidated - - WATER 0 - sand 0 19 0 PW-3 20 W. Smiley - - - - - - - - - - - Shallow - - -

REC-62 27 50' N line, 2650' W line Section 17, T. 32N., R. 9E. Bolliger, John & Sons - - - - - - - WATER 0 - - 0 0 -

PW-8 28 S. Center St. - - - - - - - - - - - Shallow bedrock - - -

PW-2 31 25131 W. Smiley Rd., Braidwood Strange, Robert E. 1/6/2005 Construction Report Domestic Drilled Unconsolidated 7 9 WATER 0 - sand/gravel 21 31 15 PW-1 32 25141 W. Smiley Rd, Braidwood Strange, Robert E. 1/6/2005 Construction Report Domestic Drilled Unconsolidated 7 9 WATER 0 - sand & gravel 22 32 15 PW-13 33 34714 Comet Dr. - - - - - - - - - - - - - - -

REC-314 38 160 Bobby Lane, COMET ESTES. Strange, Robert E. 7/6/2000 Construction Report Domestic Drilled Unconsolidated 19 29 WATER 0 - sand/gravel 33 38 10 REC-40 40 Route 113 and Park Road, Braidwood. Knierin Paul 01/25/1972 Construction Report Domestic - - - - WATER 0 - limestone 10 40 20 REC-151 40 - Anderson Well Drlg. - - - - - - - WATER 0 - - 0 0 -

PW-15 40 S. Center St. - - - - - - - - - - - Shallow sand - - -

PW-7 40 380 Comet Dr. - - - - - - - - - - - Shallow sand - - -

REC-221 48 306 Comet Dr., Braidwood Wills, Elmer D. 5/6/1991 Construction Report Domestic - Bedrock 8 - WATER 0 - sand rock 32 48 0 REC-239 50 34420S Charles Lane, Braidwood Brown, Darwin 10/21/1994 Construction Report Domestic Drilled Bedrock 9 39 WATER 0 - shale 10 50 0 REC-65 56 330'S line, 330'W line section 17, T.32N., R. 9E. Miller, J. P. Art. Well 7/00/1955 Construction Report Test Well - Bedrock - - WATER 0 - - 0 0 -

REC-180 60 Lot 27-28 Comet Estates Subd. Fykes, Charles N. 11/26/1986 Construction Report Domestic - - - - WATER 0 - sandstone 38 60 10 PW-14 60 S. Center St. - - - - - - - - - - - - - - -

PW-9 60 S. Center St. - - - - - - - - - - - - - - -

REC-67 65 - Layne Western Co., Inc. - - - - - - - WATER 0 - - 0 0 -

REC-158 65 Cemetery Road, Braidwood Fykes Charles & Pump 7/8/1978 Construction Report Domestic - - - - WATER 0 - sandstone 35 65 8 REC-201 65 - Fykes, Charles N. 07/27/1984 Construction Report Domestic - - - - WATER 593 GL sandstone 38 65 10 REC-61 75 50' N line, 1300' W line Section 17, T. 32N., R. 9E. Bolliger, John & Sons 04/00/1950 Construction Report Test Well - Bedrock - - WATER 0 - - 0 0 -

REC-73 75 Route #1 Braceville Lockport Well & Pump 2/9/1971 Construction Report Domestic - - - - WATER 0 - sandstone 43 75 10 REC-63 79 30' W line, 1800' N line Section 17, T. 32N., R. 9E. Bolliger, John & Sons - - - - - - - WATER 0 - - 0 0 -

REC-64 80 330'S line, 330'E line of NW NW section 17, T.32N., R. 9E. Miller, J. P. Art. Well 07/001955 Construction Report Test Well - Bedrock - - WATER 0 - - -

REC-99 80 311 W. Odell St. Lockport Well & Pump 12/2/1973 - - - - - - WATER 0 - limestone 50 80 10 REC-104 86 - Griffy, Cecil D. - - - - - - - WATER 0 - shale 61 86 4 REC-107 90 - Lockport Well & Pump - - - - - - - WATER 0 - sandstone 46 90 10 REC-159 100 Cemetary Road, Braidwood Fykes Charles & Pump 04/20/1978 Construction Report Domestic - - - - WATER 0 - sandstone 40 65 10 REC-66 106 - Miller, J. P. Art. Well - - - - - - - WATER 0 - - 0 0 -

REC-241 110 LOT 57 Fordonski, Keith 11/11/1994 Construction Report Domestic Drilled Bedrock 49 59 WATER 0 - shale 45 110 0 REC-277 125 360 Cemetary Rd, Braidwood Bisping, Calvin 8/10/1996 Construction Report Domestic Drilled Bedrock 20 100 WATER 0 - limestone - shale 60 125 0 REC-268 350 LOT 22 FAIR OAKS Fordonski, Keith - - - - - - - WATER 0 - shale & limestone 60 350 0 REC-275 470 LOT 21 FAIR OAKS SUBD. Fordonski, Keith 10/21/1996 Construction Report Domestic Drilled Bedrock 49 449 WATER 0 - limestone 260 470 0 PW-11 675 34711 S. Center St., Braidwood Edward Hall - Web Well & Pump 11/20/2001 Construction Report Domestic Drilled Bedrock 295 339 WATER 0 - sand 655 675 12 PW-10 680 38038 S. Center St., Braidwood Matherly, Hubert 01/28/1999 Construction Report Domestic Drilled Bedrock 339 379 WATER 0 - St. Peter 615 680 0 REC-2 1647 - Varner C W - - - - - - - WATER 577 GL - 0 0 -

PW-12 - 376 Comet Dr. - - - - - - - - - - - Shallow bedrock - - -

PW-4 - S. Center St. - - - - - - - - - - - - - - -

PW-5 - 388 Comet Dr. - - - - - - - - - - - - - - -

PW-6 - - - - - - - - - - - - - Shallow sand - - -

REC-37 - - Griffy, Cecil D. 5/11/1973 Construction Report Domestic - - - - WATER 0 - limestone, shale 71 80 20 CRA 016841 (12)

TABLE 6.1

SUMMARY

OF GENERAL WATER QUALITY IN BLOWDOWN LINE AND BACKGROUND GROUNDWATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Blowdown Line Unimpacted Groundwater Sample Location: At River Inside Plant MW-106 MW-110 Sample ID: GW-111405-DC-004 GW-111405-DC-001 GW-111405-DC-003 GW-111405-DC-002 Sample Date: Illinois Standards 11/14/2005 11/14/2005 11/14/2005 11/14/2005 Units Class I Wet Alkalinity mg/L - 320 300 170 570 Chloride mg/L 200c 96 100 ND(5) ND(5)

Nitrate mg/L 10.0c 0.14 0.12 0.28 0.21 Phosphate (as PO4) mg/L - 0.92 0.86 0.06 ND(0.01)

Phosphorous mg/L - 0.3 0.28 0.02 ND(0.01)

Sulfide mg/L - ND(0.05) ND(0.05) ND(0.05) ND(0.05)

Metals Aluminum mg/L - 0.21 0.018 0.015 0.1 Antimony mg/L 0.006 c ND(0.006) ND(0.006) ND(0.006) ND(0.006)

Arsenic mg/L 0.05c 0.006 ND(0.002) ND(0.002) 0.007 Barium mg/L 2.0c 0.034 0.035 0.016 0.098 Beryllium mg/L 0.004 c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Boron mg/L 2.0c 0.36 0.35 0.03 0.26 Cadmium mg/L 0.005 c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Calcium mg/L - 155 156 52.7 193 Chromium mg/L 0.1c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Cobalt mg/L 1.0c ND(0.001) ND(0.001) ND(0.001) 0.005 Copper mg/L 0.65c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Iron mg/L 5.0c 0.17 0.17 0.01 6.31 Lead mg/L 0.0075 c ND(0.002) ND(0.002) ND(0.002) ND(0.002)

Magnesium mg/L - 78.5 77.7 18.8 30.9 Manganese mg/L 0.15c 0.018 0.019 0.056 ND(0.001)

Molybdenum mg/L - 0.01 0.01 ND(0.01) ND(0.01)

Nickel mg/L 0.1c 0.007 ND(0.001) ND(0.001) 0.003 Potassium mg/L - 9.5 9.5 1.9 25.3 Selenium mg/L 0.05c ND(0.002) ND(0.002) ND(0.002) ND(0.002)

Silver mg/L 0.05c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Sodium mg/L - 48.4 48.1 2.70 4.9 Thallium mg/L 0.002 c ND(0.002) ND(0.002) ND(0.002) ND(0.002)

Vanadium mg/L 0.049 ND(0.01) ND(0.01) ND(0.01) ND(0.01)

Zinc mg/L 5.0c ND(0.005) ND(0.005) 0.029 0.017 c

Value listed is also the Groundwater Quality Standard for this chemical pursuant to 35 Ill. Adm. Code 620.410 for Class I Groundwater or 35 Ill. Adm. Code 620.420 for Class II Groundwater.

Exceeds Illinois Standards Class I CRA 016841 (12)

TABLE 6.2 Page 1 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

A-1 1/11/2006 33 A-1D 1/11/2006 60 B-01 2/20/2006 64 B-01D 2/20/2006 46 BL-01 11/17/2005 70 BL-02 11/17/2005 156 BL-03 11/18/2005 0 BL-04 11/18/2005 40 BL-05 11/18/2005 102 BL-06 11/18/2005 114 BL-07 11/18/2005 39 BL-08 11/18/2005 90 BL-09 12/23/2005 4701 BL-09 1/11/2006 5270 BL-09 1/18/2006 5049 BL-09 1/25/2006 4809 BL-09 2/1/2006 4689 BL-09 2/9/2006 4932 BL-09 2/15/2006 4393 BL-09 2/22/2006 4086 BL-09 3/1/2006 3404 BL-09 (recount) 3/1/2006 3486 BL-09D 12/23/2005 23097 BL-09D 1/11/2006 22016 BL-09D 1/18/2006 21230 BL-09D 1/25/2006 20383 BL-09D 2/1/2006 20171 BL-09D 2/9/2006 20428 BL-09D 2/15/2006 19778 BL-09D 2/22/2006 18018 BL-09D 3/1/2006 16980 BL-09D (recount) 3/1/2006 16403 BL-10 11/17/2005 295 BL-10 1/4/2006 -104 BL-10D 12/15/2005 8259 BL-10D (recount) 12/15/2005 7885 BL-10D 1/4/2006 7535 BL-11 11/17/2005 61 BL-11 1/3/2006 13 BL-11D 12/15/2005 -213 BL-11D 1/3/2006 -27 BL-12 11/17/2005 126 BL-12 1/3/2006 -39 BL-12D 12/15/2005 -31 BL-12D 1/3/2006 -35 BL-13 11/17/2005 76 CRA 016841 (12)

TABLE 6.2 Page 2 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

BL-13 1/3/2006 -16 BL-13D 12/15/2005 -150 BL-13D 1/3/2006 9 BL-14 11/17/2005 70 BL-14 1/3/2006 -37 BL-14D 12/15/2005 -187 BL-14D 1/3/2006 -91 BL-15 11/17/2005 1178 BL-15 1/3/2006 146 BL-15D 12/16/2005 -38 BL-15D 1/3/2006 -49 BL-16 11/17/2005 4058 BL-16 1/3/2006 3364 BL-16D 12/16/2005 -85 BL-16D 1/3/2006 -91 BL-17 12/1/2005 25 BL-17 12/5/2005 105 BL-17 12/6/2005 183 BL-17 1/3/2006 -44 BL-17D 12/12/2005 28 BL-17D 1/3/2006 -126 BL-18 12/1/2005 108 BL-18D 2/7/2006 121 BL-19 12/1/2005 37 BL-19D 2/7/2006 95 BL-20D 12/23/2005 -76 BL-20D 1/4/2006 -117 C-1 12/12/2005 85 C-1 1/3/2006 -80 C-1D 12/12/2005 158 C-1D 1/3/2006 -140 C-2 1/24/2006 -48 C-2 2/1/2006 105 C-2 2/9/2006 162 C-2 2/15/2006 38 C-2 2/22/2006 82 C-2D 1/24/2006 147 C-2D 2/1/2006 221 C-2D 2/9/2006 320 C-2D 2/15/2006 351 C-2D 2/22/2006 589 D-1 12/6/2005 92 D-1 1/4/2006 -13 D-1D 12/23/2005 -147 D-1D 1/4/2006 -141 D-2 12/5/2005 125 CRA 016841 (12)

TABLE 6.2 Page 3 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

D-2 12/6/2005 59 D-2 1/4/2006 -165 D-2D 12/23/2005 -91 D-2D 1/4/2006 -36 D-3 12/2/2005 137 D-3 1/4/2006 -168 D-3D 12/23/2005 4674 D-3D 1/4/2006 5110 D-4 12/6/2005 91 D-5 12/2/2005 73 Ditch at Culvert 12/22/2005 1007 Ditch at Culvert 2/15/2006 468 Ditch at Culvert 2/22/2006 306 Ditch at Culvert 3/1/2006 670 Ditch by Alpha Gate 1/12/2006 -30 Ditch by Alpha Gate 1/19/2006 107 Ditch by Alpha Gate 1/26/2006 77 Ditch by Alpha Gate 2/2/2006 23 Ditch by Alpha Gate 2/9/2006 201 Ditch by Alpha Gate 2/16/2006 123 Ditch by GW-1 2/15/2006 36 Ditch by GW-1 2/22/2006 100 Ditch by GW-1 3/1/2006 -10 DS-10 5/20/2005 49 DS-11 5/5/2005 28 DS-11 5/27/2005 ND()

DS-1a 5/10/2005 44 DS-1b 5/10/2005 10 DS-1b 5/27/2005 40 DS-1b 7/14/2005 59 DS-1b 9/22/2005 -2.34 DS-2 5/5/2005 438 DS-2 5/27/2005 682 DS-2 7/14/2005 1690 DS-2 9/22/2005 1740 DS-3 5/27/2005 786 DS-3 6/14/2005 35 DS-3 7/14/2005 226 DS-3 9/22/2005 289 DS-4 6/14/2005 99 DS-4 7/14/2005 -22.6 DS-4 9/22/2005 72.3 DS-5 7/14/2005 -46.2 DS-5 9/22/2005 -41.1 DS-6 5/20/2005 65 DS-7 5/27/2005 78 CRA 016841 (12)

TABLE 6.2 Page 4 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

DS-8 5/10/2005 51 DS-8 5/27/2005 166 DS-9 5/20/2005 65 F-1 12/12/2005 104 F-1 1/3/2006 -44 F-1D 12/12/2005 139 F-1D 1/3/2006 -56 F-2D 1/9/2006 684 F-2D 1/12/2006 546 F-3D 1/9/2006 1689 F-3D 1/12/2006 1689 F-4D 1/24/2006 -22 F-5D 1/24/2006 1512 F-6D 1/24/2006 689 F-7D 1/24/2006 575 F-8D 1/24/2006 872 G-1 12/6/2005 133 G-2 12/6/2005 87 G-2D 1/26/2006 67 G-3 12/6/2005 81 GW-1 2/9/2006 20 GW-2 2/9/2006 57 MW-101 3/24/2005 41 MW-101 7/28/2005 -397 MW-101 10/19/2005 -52.8 MW-101 11/15/2005 157 MW-102 3/24/2005 58 MW-103 3/24/2005 132 MW-103 8/15/2005 3010 MW-103 10/20/2005 2660 MW-103 11/15/2005 2497 MW-104 3/24/2005 397 MW-104 7/28/2005 142 MW-105 7/28/2005 563 MW-105 10/17/2005 384 MW-105 11/15/2005 729 MW-105 1/4/2006 169 MW-105D 12/16/2005 -69 MW-105D 1/4/2006 -120 MW-106 7/28/2005 8.77 MW-106 1/4/2006 -35 MW-106D 12/16/2005 -115 MW-106D 1/4/2006 -25 MW-107 7/28/2005 158 MW-107 9/30/2005 124 MW-107 10/17/2005 129 CRA 016841 (12)

TABLE 6.2 Page 5 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

MW-107 11/15/2005 269 MW-108 7/28/2005 18.2 MW-108 9/30/2005 43.8 MW-108 10/17/2005 -29.4 MW-108 11/15/2005 91 MW-109 7/28/2005 238 MW-109 9/30/2005 305 MW-110 10/20/2005 137 MW-110 11/15/2005 93 MW-110 1/4/2006 -104 MW-111 10/19/2005 -44.0 MW-111 11/15/2005 224 MW-111 1/4/2006 -78 MW-111D 1/9/2006 -66 MW-112 10/19/2005 -33.0 MW-112 11/15/2005 167 MW-112 1/4/2006 -127 MW-112D 1/9/2006 -111 MW-113 10/19/2005 4480 MW-113 11/15/2005 4830 MW-113 12/5/2005 4009 MW-113 12/6/2005 3598 MW-113 1/3/2006 4008 MW-113D 12/14/2005 4835 MW-113D 1/3/2006 4772 P-1 12/1/2005 2484 P-2 12/2/2005 4344 P-2 1/3/2006 2045 P-2D 12/12/2005 2599 P-2D 1/3/2006 2384 P-3 12/2/2005 3258 P-4 12/1/2005 33041 P-4 12/6/2005 25311 P-4 1/3/2006 19317 P-4 1/11/2006 15937 P-4 1/18/2006 12165 P-4 1/25/2006 9588 P-4 2/1/2006 6621 P-4 2/9/2006 4412 P-4 2/15/2006 3045 P-4 3/1/2006 3479 P-4D 12/23/2005 59592 P-4D 1/3/2006 48493 P-4D 1/11/2006 47095 P-4D 1/18/2006 50308 P-4D 1/25/2006 38965 CRA 016841 (12)

TABLE 6.2 Page 6 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

P-4D 2/1/2006 32551 P-4D 2/9/2006 34828 P-4D 2/15/2006 39339 P-4D 2/22/2006 44547 P-4D 3/1/2006 45640 P-4D (recount) 3/1/2006 40895 P-4S 2/22/2006 2841 P-5 12/1/2005 6621 P-5 1/3/2006 6166 P-5D 12/23/2005 2402 P-5D 1/3/2006 2165 P-6 12/1/2005 450 P-6 1/18/2006 110 P-7 12/1/2005 1210 P-8 12/1/2005 2998 P-8 12/6/2005 2212 P-9 12/5/2005 1346 P-9 12/6/2005 -90 P-9 12/13/2005 111 P-9 (recount) 12/13/2005 27 P-10 12/5/2005 1934 P-10 12/6/2005 1723 P-11 12/5/2005 1681 P-11 12/6/2005 1476 P-12 12/5/2005 1535 P-12 12/6/2005 1622 P-13D 12/23/2005 226468 P-13D (recount) 12/28/2005 225231 P-13D 1/3/2006 228283 P-13D 1/11/2006 229838 P-13D 1/18/2006 223754 P-13D 1/25/2006 217122 P-13D 2/1/2006 226034 P-13D 2/9/2006 233668 P-13D 2/15/2006 229926 P-13D 2/22/2006 230133 P-13D 3/1/2006 230793 P-13D (recount) 3/1/2006 214892 P-14 1/24/2006 2537 P-14D 1/24/2006 2388 PS-1 12/22/2005 -18 PS-1 1/4/2006 -89 PS-2 12/22/2005 -89 PS-2 1/4/2006 15 PS-3 1/4/2006 -137 PS-4 1/10/2006 30 CRA 016841 (12)

TABLE 6.2 Page 7 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

PS-6 1/12/2006 287 RW-1 12/1/2005 2396 RW-1 12/4/2005 7855 RW-2 12/1/2005 33736 RW-2 12/4/2005 88778 RW-2 (10 ft) 12/13/2005 54111 RW-2 (10.6 ft) 12/6/2005 58621 RW-2 (20 ft) 12/13/2005 171166 RW-2 (20.6 ft) 12/6/2005 170024 RW-2 (25 ft) 12/6/2005 223888 RW-2 (25 ft) 12/13/2005 246442 RW-3 12/2/2005 197 RW-4 12/2/2005 380 S-1 12/5/2005 -21 S-1 12/6/2005 83 S-1D 1/26/2006 1287 S-2 12/5/2005 95 S-2 12/6/2005 88 S-2 1/3/2006 62 S-2 2/1/2006 183 S-2 2/9/2006 237 S-2 2/15/2006 190 S-2 2/22/2006 172 S-2 3/1/2006 85 S-2D 12/12/2005 225 S-2D 1/3/2006 -2 S-2D 2/1/2006 193 S-2D 2/9/2006 177 S-2D 2/15/2006 185 S-2D 2/22/2006 168 S-2D 3/1/2006 74 S-3 12/5/2005 145 S-3 12/6/2005 57 S-4 12/5/2005 1280 S-4 12/6/2005 1086 S-4D 1/26/2006 2111 S-5 12/5/2005 2023 S-5 12/6/2005 1874 S-6 12/5/2005 679 S-6 12/6/2005 411 S-7 1/24/2006 1373 S-7D 1/24/2006 1546 SG-1 7/28/2005 61.3 SG-2 7/28/2005 1970 SG-3 7/28/2005 -21.4 SW-1 11/30/2005 2464 CRA 016841 (12)

TABLE 6.2 Page 8 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

SW-2 11/30/2005 2347 SW-2 1/11/2006 2938 SW-2 1/18/2006 2504 SW-2 1/25/2006 2441 SW-2 2/1/2006 2626 SW-2 2/15/2006 2434 SW-2 2/22/2006 808 SW-2 3/1/2006 2243 SW-2 (recount) 3/1/2006 2142 SW-3 12/2/2005 96 SW-4 12/2/2005 83 SW-5 1/30/2006 76 SW-6 2/9/2006 41 VB-1 5/27/2005 51295 VB-1-1 11/15/2005 1194 VB-1-1 1/4/2006 425 VB-1-1D 12/16/2005 -49 VB-1-1D 1/4/2006 -132 VB-1-2 11/17/2005 337 VB-1-2D 1/13/2006 238 VB-1-3 11/15/2005 206 VB-1-3D 1/13/2006 19431 VB-1-4 11/15/2005 384 VB-1-4D 1/13/2006 7424 VB-1-5 11/15/2005 130 VB-1-5D 1/13/2006 22928 VB-1-6 11/22/2005 95 VB-1-6D 1/13/2006 41 VB-1-7 11/22/2005 140 VB-1-7D 1/9/2006 -116 VB-1-8 11/22/2005 57 VB-1-8D 1/9/2006 10877 VB-1-9 11/22/2005 107 VB-1-9D 1/13/2006 3370 VB-2-1 11/15/2005 207 VB-2-2 11/15/2005 6193 VB-2-2 12/5/2005 5832 VB-2-2 12/6/2005 5569 VB-2-2 1/4/2006 5232 VB-2-2D 12/23/2005 3445 VB-2-2D 1/4/2006 4037 VB-2-3 11/15/2005 3940 VB-2-4 11/15/2005 3664 VB-2-5 11/15/2005 4270 VB-2-5 1/3/2006 3834 VB-2-5D 12/14/2005 64 CRA 016841 (12)

TABLE 6.2 Page 9 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

VB-2-5D 1/3/2006 102 VB-2-6 11/15/2005 2132 VB-2-6 12/5/2005 2348 VB-2-6 12/6/2005 1979 VB-2-6 1/3/2006 1412 VB-2-6D 12/14/2005 56 VB-2-6D 1/3/2006 44 VB-2-7 12/14/2005 -47 VB-2-7 1/4/2006 -60 VB-2-7D 12/14/2005 -52 VB-2-7D 1/4/2006 -53 VB-2-8 12/14/2005 -103 VB-2-9 1/12/2006 78 VB-2-9D 1/12/2006 -65 VB-3 5/11/2005 1521 VB-3-1 11/15/2005 5959 VB-3-10 12/16/2005 8473 VB-3-10 1/3/2006 12076 VB-3-10D 12/16/2005 70773 VB-3-10D 1/3/2006 108736 VB-3-2 11/15/2005 32830 VB-3-2 (repeat) 11/15/2005 26686 VB-3-3 11/16/2005 43894 VB-3-4 11/16/2005 58489 VB-3-4 12/5/2005 43708 VB-3-4 12/6/2005 40654 VB-3-4 1/3/2006 29286 VB-3-4D 12/14/2005 747 VB-3-4D 1/3/2006 790 VB-3-5 11/22/2005 95 VB-3-6 11/22/2005 53572 VB-3-7 12/2/2005 169 VB-3-7 1/3/2006 -126 VB-3-7D 12/14/2005 -79 VB-3-7D 1/3/2006 -205 VB-3-8 12/2/2005 171 VB-3-9D 12/13/2005 21715 VB-3-9D 1/4/2006 19605 1

Results through March 1, 2006 CRA 016841 (12)

TABLE 6.3 Page 1 of 2

SUMMARY

OF WEEKLY RESULTS FOR TRITIUM IN KEY MONITORING WELLS 1

AND THE PERIMETER DITCH EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

BL-09 12/23/2005 4701 BL-09 1/11/2006 5270 BL-09 1/18/2006 5049 BL-09 1/25/2006 4809 BL-09 2/1/2006 4689 BL-09 2/9/2006 4932 BL-09 2/15/2006 4393 BL-09 2/22/2006 4086 BL-09 3/1/2006 3404 BL-09 (recount) 3/1/2006 3486 BL-09D 12/23/2005 23097 BL-09D 1/11/2006 22016 BL-09D 1/18/2006 21230 BL-09D 1/25/2006 20383 BL-09D 2/1/2006 20171 BL-09D 2/9/2006 20428 BL-09D 2/15/2006 19778 BL-09D 2/22/2006 18018 BL-09D 3/1/2006 16980 BL-09D (recount) 3/1/2006 16403 C-2 1/24/2006 -48 C-2 2/1/2006 105 C-2 2/9/2006 162 C-2 2/15/2006 38 C-2 2/22/2006 82 C-2D 1/24/2006 147 C-2D 2/1/2006 221 C-2D 2/9/2006 320 C-2D 2/15/2006 351 C-2D 2/22/2006 589 Ditch by Alpha Gate 1/12/2006 -30 Ditch by Alpha Gate 1/19/2006 107 Ditch by Alpha Gate 1/26/2006 77 Ditch by Alpha Gate 2/2/2006 23 Ditch by Alpha Gate 2/9/2006 201 Ditch by Alpha Gate 2/16/2006 123 P-4 12/1/2005 33041 P-4 12/6/2005 25311 P-4 1/3/2006 19317 P-4 1/11/2006 15937 P-4 1/18/2006 12165 P-4 1/25/2006 9588 P-4 2/1/2006 6621 P-4 2/9/2006 4412 P-4 2/15/2006 3045 P-4 3/1/2006 3479 P-4D 12/23/2005 59592 P-4D 1/3/2006 48493 CRA 016841 (12)

TABLE 6.3 Page 2 of 2

SUMMARY

OF WEEKLY RESULTS FOR TRITIUM IN KEY MONITORING WELLS 1

AND THE PERIMETER DITCH EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

P-4D 1/11/2006 47095 P-4D 1/18/2006 50308 P-4D 1/25/2006 38965 P-4D 2/1/2006 32551 P-4D 2/9/2006 34828 P-4D 2/15/2006 39339 P-4D 2/22/2006 44547 P-4D 3/1/2006 45640 P-4D (recount) 3/1/2006 40895 P-13D 12/23/2005 226468 P-13D (recount) 12/28/2005 225231 P-13D 1/3/2006 228283 P-13D 1/11/2006 229838 P-13D 1/18/2006 223754 P-13D 1/25/2006 217122 P-13D 2/1/2006 226034 P-13D 2/9/2006 233668 P-13D 2/15/2006 229926 P-13D 2/22/2006 230133 P-13D 3/1/2006 230793 P-13D (recount) 3/1/2006 214892 S-2 12/5/2005 95 S-2 12/6/2005 88 S-2 1/3/2006 62 S-2 2/1/2006 183 S-2 2/9/2006 237 S-2 2/15/2006 190 S-2 2/22/2006 172 S-2 3/1/2006 85 S-2D 12/12/2005 225 S-2D 1/3/2006 -2 S-2D 2/1/2006 193 S-2D 2/9/2006 177 S-2D 2/15/2006 185 S-2D 2/22/2006 168 S-2D 3/1/2006 74 SW-2 11/30/2005 2347 SW-2 1/11/2006 2938 SW-2 1/18/2006 2504 SW-2 1/25/2006 2441 SW-2 2/1/2006 2626 SW-2 2/15/2006 2434 SW-2 2/22/2006 808 SW-2 3/1/2006 2243 SW-2 (recount) 3/1/2006 2142 1

Results through March 1, 2006 CRA 016841 (12)

TABLE 6.4

SUMMARY

OF TRITIUM CONCENTRATIONS IN PRIVATE WELLS 1 EXELON GENERATION BRAIDWOOD STATION Monitoring Location Date Tritium Result (pCi/L)

PW-1 11/30/2005 -26 PW-2 11/30/2005 48 PW-3 11/30/2005 25 PW-3 2/2/2006 -63 PW-4 12/2/2005 43 PW-5 12/7/2005 9 PW-5 1/19/2006 -12 PW-5 1/30/2006 28 PW-6 2/2/2006 -4 PW-6P2 12/8/2005 142 2

PW-6P 2/7/2006 128 PW-7 12/7/2005 -58 PW-8 12/3/2005 1151 PW-8 12/6/2005 1524 PW-8 12/8/2005 1367 PW-9 12/5/2005 142 PW-10 12/7/2005 72 PW-11 12/5/2005 99 PW-11 2/2/2006 12 PW-12 12/7/2005 44 PW-13 12/7/2005 -62 PW-13 1/30/2006 38 PW-14 12/14/2005 -118 PW-14 1/30/2006 56 PW-15 12/14/2005 -51 1

Results through March 1, 2006 2

Surface water (pond) sample CRA 016841 (12)

TABLE 6.5

SUMMARY

OF INDICATOR PARAMETER SAMPLES IN THE BLOWDOWN LINE, BACKGROUND GROUNDWATER, AND MONITORING WELLS NEAR THE BLOWDOWN LINE EXELON GENERATION BRAIDWOOD STATION Monitoring Location: Sample Date: Sodium (mg/L) Chloride (mg/L)

At River (blowdown line) 11/14/2005 48.4 96 Inside Plant (blowdown line) 11/14/2005 48.1 100 MW-106 (unimpacted) 11/14/2005 2.70 ND(5)

MW-110 (unimpacted) 11/14/2005 4.9 ND(5)

BL-01 11/18/2005 2.5 ND(5)

BL-02 11/18/2005 3.3 6 BL-03 11/18/2005 2.8 ND(5)

BL-04 11/18/2005 4.3 ND(5)

BL-05 11/18/2005 5.7 8 BL-06 11/18/2005 2.8 ND(5)

BL-07 11/18/2005 2.8 16 BL-08 11/18/2005 1.6 ND(5)

BL-10 11/18/2005 10.8 ND(5)

BL-10D 12/15/2005 22.6 26 BL-11 11/18/2005 2.3 ND(5)

BL-11D 12/15/2005 4.7 6.0 BL-12 11/18/2005 2.6 ND(5)

BL-12D 12/15/2005 3.5 5.0 BL-13 11/18/2005 2.1 ND(5)

BL-13D 12/15/2005 2.8 ND(5)

BL-14 11/18/2005 2.6 ND(5)

BL-14D 12/15/2005 3.0 5.0 BL-15 11/18/2005 8.9 6 BL-15D 12/16/2005 3.0 ND(5)

BL-16 11/18/2005 2.6 54 BL-16D 12/16/2005 2.4 ND(5)

BL-17D 12/13/2005 3.5 ND(5)

MW-105D 12/16/2005 2.6 5.0 CRA 016841 (12)

APPENDIX A CORRESPONDENCE BETWEEN EXELON AND THE IEPA BUREAU OF WATER 016841 (12)

TRITIUM INVESTIGATION EXELON GENERATION - BRAIDWOOD STATION BRACEVILLE, ILLINOIS MARCH 2006 REF. NO. 016841 (12)

This report is printed on recycled paper.

TABLE OF CONTENTS Page EXECUTIVE

SUMMARY

.................................................................................................................... i

1.0 INTRODUCTION

...................................................................................................................1 2.0 SITE DESCRIPTION ...............................................................................................................3 2.1 SITE LOCATION AND DEFINITION OF BOUNDARIES ...........................3 2.2 OVERVIEW OF BRAIDWOOD STATION OPERATIONS...........................3 2.3 SURROUNDING LAND USE ...........................................................................4 2.4 OVERVIEW OF GROUNDWATER USE IN THE SITE AREA.....................4

3.0 BACKGROUND

INFORMATION ON THE RELEASES OF TRITIUM .........................6 3.1 BLOWDOWN LINE OPERATION AND RADWASTE TANK DISCHARGES..............................6 3.1.1 BLOWDOWN LINE DESCRIPTION AND PURPOSE ..................................6 3.

1.2 DESCRIPTION

OF THE VACUUM BREAKER VALVES .............................7 3.1.3 PERMITTED DISCHARGES FROM RADWASTE TANKS ..........................7 3.

1.4 DESCRIPTION

OF THE SOURCE OF TRITIUM............................................8 3.2 HISTORY OF VACUUM BREAKER RELEASES............................................8 3.3 PREVIOUS GROUNDWATER STUDIES ......................................................11 3.3.1 POWER PLANT DOCUMENTS - UFSAR REPORT ....................................11 3.3.2 2000 DIESEL FUEL RESPONSE ......................................................................11 3.3.3 2005 INVESTIGATIONS OF TRITIUM IN GROUNDWATER AND SURFACE WATER........................12 3.4 CURRENT REGULATORY STATUS .............................................................13 3.4.1 NPDES AND NRC PERMITS FOR THE BLOWDOWN LINE...................13 3.4.2 DECEMBER 2005 VIOLATION NOTICE ......................................................13 3.4.3 REGULATORY AGENCY COORDINATION ..............................................14 4.0 SITE-SPECIFIC SAMPLING PLAN -

GROUNDWATER INVESTIGATION OF TRITIUM.......................................................16 4.1 PURPOSE AND SEQUENCE OF INVESTIGATIONS................................16 4.2 FIELD STUDIES COMPLETED TO DATE ....................................................17 4.2.1 PERMANENT MONITORING WELL INSTALLATION............................17 4.2.2 PERMANENT MONITORING WELL DEVELOPMENT ...........................18 4.2.3 TEMPORARY MONITORING WELL INSTALLATION ............................18 4.2.4 TEMPORARY MONITORING WELL DEVELOPMENT ............................18 4.2.5 INSTALLATION OF RECOVERY WELLS ....................................................18 4.2.6 RECOVERY WELL DEVELOPMENT ............................................................19 4.2.7 GROUNDWATER AND SURFACE WATER LEVEL MEASUREMENTS ...............................................................19 4.2.8 GROUNDWATER SAMPLING AND ANALYSES......................................19 4.2.8.1 OTHER RADIOISOTOPE ANALYSIS OF GROUNDWATER ...................20 4.2.9 SURFACE WATER SAMPLING .....................................................................21 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

TABLE OF CONTENTS Page 4.2.10 PRIVATE WATER WELL SAMPLING PROGRAMS ..................................21 4.2.11 SINGLE WELL AQUIFER TESTING..............................................................21 4.3 AREA WIDE WATER WELL INVENTORY.................................................22 4.4 REGIONAL HYDROGEOLOGIC DATA COLLECTION ...........................22 4.5 SAMPLING AND ANALYSIS RELATED TO TRITIUM DATING ...........22 5.0 DOCUMENTATION OF FIELD ACTIVITIES -

PRESENTATION OF STUDIES AND ANALYSES COMPLETED TO DATE .............24 5.1 PHYSICAL SITE SETTING ..............................................................................24 5.1.1 REGIONAL TOPOGRAPHY AND SURFACE WATER FEATURES ........24 5.1.2 REGIONAL GEOLOGY ...................................................................................24 5.1.3 REGIONAL HYDROGEOLOGY.....................................................................25 5.1.4 SITE-SPECIFIC TOPOGRAPHY AND SURFACE WATER FEATURES ..26 5.1.5 SITE-SPECIFIC GEOLOGY..............................................................................26 5.1.6 SITE-SPECIFIC HYDROGEOLOGY ...............................................................27

6.0 DESCRIPTION

OF THE CHEMICALS OF CONCERN AND SOURCE AREAS........29 6.1 GENERAL TRITIUM CHARACTERISTICS..................................................29 6.2 CHARACTERISTICS OF WATER IN THE BLOWDOWN LINE - COOLING LAKE WATER QUALITY....................30 6.3 DISTRIBUTION OF TRITIUM IN GROUNDWATER AT THE SITE ........31 6.4 CONCEPTUAL MODEL OF TRITIUM RELEASE AND MIGRATION ...32 7.0 ENDANGERMENT ASSESSMENT ...................................................................................36 7.1 HEALTH EFFECTS OF TRITIUM...................................................................36 7.2 GROUNDWATER STANDARD .....................................................................37 7.3 SITE SPECIFIC BACKGROUND CONCENTRATIONS OF TRITIUM IN GROUNDWATER .......................38 7.4 EXPOSURE ROUTE EVALUATIONS............................................................39 7.4.1 IDENTIFICATION OF POTENTIAL EXPOSURE PATHWAYS AND POTENTIAL RECEPTORS ....................................................................39 7.4.1.1 DIRECT DISCHARGE SCENARIO ................................................................39 7.4.1.2 OVERFLOW SCENARIO .................................................................................40 7.5

SUMMARY

OF EXPOSURE ROUTES............................................................44

8.0 CONCLUSION

S....................................................................................................................46 9.0 PLAN OF ACTION...............................................................................................................48 9.1 FILL DATA GAPS .............................................................................................48 9.2 GROUNDWATER MONITORING ................................................................48 9.3 REMEDIATION.................................................................................................48

10.0 REFERENCES

CITED...........................................................................................................51 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

LIST OF FIGURES (Following Text)

FIGURE 1.1 SITE LOCATION MAP FIGURE 2.1 GENERAL SITE BOUNDARIES AND FEATURES FIGURE 2.2 PRIVATE WATER SUPPLY WELL LOCATIONS FIGURE 3.1 SCHEMATICS OF THE BLOWDOWN LINE AND VACUUM BREAKERS FIGURE 4.1 GROUNDWATER MONITORING LOCATIONS FIGURE 4.2 SURFACE WATER MONITORING LOCATIONS FIGURE 5.1 REGIONAL STRATIGRAPHIC SECTION FIGURE 5.2 REGIONAL DEEP BEDROCK GROUNDWATER LEVEL CONTOURS FIGURE 5.3 SITE SPECIFIC GEOLOGIC CROSS - SECTION FIGURE 5.4 ESTIMATED BOTTOM OF SAND/TOP OF CLAY MAP CONTOURS FIGURE 5.5 VERTICAL GROUNDWATER GRADIENTS ALONG BLOWDOWN LINE FIGURE 5.6 GROUNDWATER LEVEL CONTOURS - JANUARY 2006 - SHALLOW GROUNDWATER ZONE FIGURE 5.7 GROUNDWATER LEVEL CONTOURS - JANUARY 2006 - DEEP GROUNDWATER ZONE FIGURE 6.1 ESTIMATED TRITIUM RESULTS - SHALLOW GROUNDWATER ZONE FIGURE 6.2 ESTIMATED TRITIUM RESULTS - DEEP GROUNDWATER ZONE FIGURE 6.3 MAXIMUM DETECTIONS OF TRITIUM IN THE SHALLOW GROUNDWATER ZONE THROUGH JANUARY 2006 FIGURE 6.4 MAXIMUM DETECTIONS OF TRITIUM IN THE DEEP GROUNDWATER ZONE THROUGH JANUARY 2006 FIGURE 6.5 HYDROGEOLOGIC PROFILE LOCATIONS 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

LIST OF FIGURES (Following Text)

FIGURE 6.6 SITE SPECIFIC HYDROGEOLOGIC PROFILE - JANUARY 2006 (A-A)

FIGURE 6.7 SITE SPECIFIC HYDROGEOLOGIC PROFILE - JANUARY 2006 (B-B)

FIGURE 6.8 MAXIMUM DETECTIONS OF TRITIUM THROUGH JANUARY 2006 IN PRIVATE WELLS FIGURE 7.1 GRAPHICAL PRESENTATION OF BIOSCREEN MODELING RESULTS AND LOCATION OF WATER SUPPLY WELLS 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

LIST OF TABLES (Following Text)

TABLE 4.1

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS TABLE 4.2

SUMMARY

OF GROUNDWATER ELEVATIONS TABLE 4.3

SUMMARY

OF MONITORING WELL PURGING PARAMETERS TABLE 4.4

SUMMARY

OF PRIVATE WATER WELLS DOWNGRADIENT OF THE SITE TABLE 5.1

SUMMARY

OF VERTICAL GRADIENTS AT WELL CLUSTER LOCATIONS TABLE 6.1

SUMMARY

OF GENERAL WATER QUALITY IN BLOWDOWN LINE AND BACKGROUND GROUNDWATER SAMPLES TABLE 6.2

SUMMARY

OF TRITIUM CONCENTRATIONS IN MONITORING WELLS AND SURFACE WATER SAMPLES TABLE 6.3

SUMMARY

OF WEEKLY RESULTS FOR TRITIUM IN KEY MONITORING WELLS AND THE PERIMETER DITCH TABLE 6.4

SUMMARY

OF TRITIUM CONCENTRATIONS IN PRIVATE WELLS TABLE 6.5

SUMMARY

OF INDICATOR PARAMETER SAMPLES IN THE BLOWDOWN LINE, BACKGROUND GROUNDWATER, AND MONITORING WELLS NEAR THE BLOWDOWN LINE 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

LIST OF APPENDICES APPENDIX A CORRESPONDENCE BETWEEN EXELON AND THE IEPA BUREAU OF WATER APPENDIX B FIELD PROCEDURES APPENDIX C MONITORING WELL STRATIGRAPHIC AND INSTRUMENTATION LOGS APPENDIX D RESULTS FROM RADIOISOTOPE ANALYSES (ON CD)

D.1 TRITIUM D.2 OTHER RADIOISOTOPES APPENDIX E ENVIRONMENTAL, INC. QUALITY ASSURANCE PROGRAM APPENDIX F HYDRAULIC CONDUCTIVITY ANALYSES APPENDIX G WATER WELL INVENTORY RECORDS APPENDIX H TRITIUM DATING REPORT BY DR. POREDA APPENDIX I INFORMATION ON COAL MINING ACTIVITIES IN THE SITE AREA APPENDIX J LABORATORY ANALYSES OF GENERAL CHEMISTRY IN THE BLOWDOWN LINE AND GROUNDWATER APPENDIX K CALCULATIONS OF TRITIUM MASS IN GROUNDWATER APPENDIX L BIOSCREEN MODELING RESULTS OF TRITIUM TRANSPORT 016841 (12) CONESTOGA-ROVERS & ASSOCIATES

EXECUTIVE

SUMMARY

Conestoga-Rovers & Associates (CRA) has prepared this Focused Site Characterization Report (FSCR) for Exelon Generation Company, LLC (Exelon) to document findings with regard to the release of tritium into the groundwater at or in the vicinity of the Exelon Braidwood Nuclear Power Station (Braidwood Station) in Braceville, Illinois.

The purpose of this report is to provide a summary of Site characteristics as they relate to the sources, migration pathways, and extent of tritium in groundwater at the Braidwood Station Site. Tritium is the chemical of concern in this focused investigation because it is the only constituent of the releases that exceeds groundwater standards.

This report is the first step taken to pursue cleanup of tritium in the groundwater in a process that is in general compliance with 35 IAC 740 and meets the requirements of 35 IAC 742 Tiered Approach to Corrective Action Objective (TACO). 1 The Site, for the purposes of this FSCR, is defined as the areas of tritium-impacted groundwater resulting from past releases of blowdown line water to groundwater at vacuum breakers (VB) 1, 2, & 3. This FSCR is for an area of investigation bordered by the main generating facility to the west, the Cooling Lake to the south, Comet Drive/Cemetery Road to the east, and Route 53 to the northwest.

Hydrogeology Groundwater use in the Site area is both in the sand aquifer (20 to 30 feet deep) and in the deeper bedrock formations used regionally for municipal and private water supplies (depths of 600 to 1,700 feet). The shallow groundwater flows beneath the Site in a generally south to north manner, flowing from the Cooling Lake toward the ponds located north of the Braidwood Station property. The depth to water in this upper shallow sand aquifer ranges from 5 to 15 feet across the Site. The deeper bedrock water supply aquifers are separated from the shallow system by a number of regional aquitards. These barriers include the Wedron Till Formation (located just beneath the shallow sands) and various shale formations including the Scales Shale, which is over 70 feet thick at the Site and found at depths of 400 feet.

1 This report has many references to Illinois environmental statutes and regulations. By referring to them, we do not intend to imply that they actually apply to the Braidwood tritium releases or have any legal force or effect with respect to these releases. We take no position on this issue. We recognize that the Braidwood plant operates under a license issued by the Nuclear Regulatory Commission and is subject to NRC regulation. We also understand that Exelon Generation Company, LLC takes the position that NRC regulations, rather than Illinois statutes and regulations, apply to the tritium releases.

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Source of the Tritium The Site is transversed by the Cooling Lake blowdown line. Within the boundary of the Site, there are three vacuum breaker valves which were installed on the line to prevent damage caused by any vacuum that occurs in the pipe. Braidwood Station uses the blowdown line to return water from the Station Cooling Lake back to the Kankakee River to reduce the dissolved mineral concentration of the water in the lake. The flow in this line historically has ranged from 8,000 to 25,000 gallons per minute. This blowdown line also serves as a permitted discharge point for the Station's sewage treatment plant and the liquid radwaste system under NPDES Permit No. IL0048321.

Under normal operating conditions at Braidwood Station, the principal radionuclide discharged from the plant is tritium. The excess plant water that contains tritium is collected in a liquid radwaste tank and then released periodically to the blowdown line, which discharges to the Kankakee River. The water flowing continuously in the blowdown line contains either:

• only lake water that contains ambient tritium; or

• elevated concentrations of tritium if the radwaste tank is discharging or had just discharged to the line. The source of tritium in the blowdown line is from these intermittent and short duration discharges from the liquid radwaste tank.

For purposes of this report, the specific "Recognized Environment Concerns" at the Site are historic failures of three vacuum breaker valves (VB-1, VB-2, and VB-3), which resulted in the release of tritium to the groundwater beneath the Site. Braidwood Station records, coupled with the existing groundwater data, indicate that the tritium detected in the groundwater in 2005 and 2006 is a direct result of failures at these vacuum breaker valves, which resulted in subsurface and surface releases of blowdown line water at VB-1 (1996, 2000, and 2005), VB-2 (2000), and VB-3 (1998). Pipe integrity testing and groundwater studies along the full length of the blowdown line at the Site do not indicate that the line (pipe) itself is the source of the tritium.

Scope of Work Exelon's initial studies, in the early spring of 2005 found tritium in surface water and groundwater at the Station. These initial studies included sampling private wells to the west of the Site within the Village of Godley and sampling surface water from the perimeter ditch as it flows from east to southwest around the main generating station.

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The discovery of tritium at concentrations that exceeded the ambient (natural for this region) concentrations in the perimeter ditch on the east side of the Braidwood Station property prompted a series of groundwater studies in the summer and fall of 2005.

Exelon implemented an aggressive and comprehensive groundwater investigation program in mid-November 2005. This program also included pipe integrity testing over the full length of the blowdown line. As part of the groundwater studies and the overall groundwater characterization program 2 Exelon has installed over 265 groundwater monitoring points, collected over 420 groundwater samples and surface water samples, and sampled over 47 private wells on multiple occasions. At this specific Site, in the area of vacuum breakers VB-1, VB-2, and VB-3, Exelon has installed 160 permanent and temporary wells and collected over 370 groundwater and surface water samples.

Currently, Exelon is continuing an on-going program of private well sampling and monitoring well sampling at the Site.

The results of the groundwater and surface water studies are presented in this Focused Site Characterization Report. Based on the results of our investigation, CRA concludes:

• Groundwater flow in the shallow sand aquifer, where the tritium is detected, is from south to north;

• Groundwater flow is influenced by the perimeter ditch and by the ponds located to the north and off the Braidwood Station property;

• The underlying deeper groundwater supply aquifers are separated from the tritium in the shallow sand aquifer by the regional Wedron Formation (clayey till) and multiple shale formations, including the 70 foot thick Scales Shale;

• Groundwater flowing from the area on the Braidwood Station property south of Smiley Road discharges into the large pond located to the north;

• The distribution of tritium (and Cooling Lake water indicators) in groundwater is consistent with historical releases from three vacuum breakers on the Site;

• The Braidwood Station records of valve failures and releases of water from the three subject vacuum breakers correlate well with the current distribution of tritium in groundwater;

• At two small areas on the Site tritium concentrations exceed the 35 IAC 620 groundwater standard (20,000 picocuries per liter (pCi/L)). The first area is approximately 4.5 acres near Smiley Road, at the southeast corner of the pond and just west of the blowdown line as it leaves the Station property. The second area is located north of VB-1 and is less than 2.0 acres.

2 For this Site and other areas at the Braidwood Station (e.g., along the blowdown line and the other vacuum breakers).

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• The data collected to date indicates that tritium at concentrations which exceeds the background concentrations (approximately 200 pCi/L) has migrated into and through the pond north of Smiley Road. The distance from vacuum breakers 2 and 3 to the leading edge of this tritium that exceeds the ambient concentration is approximately 2,400 to 2,800 feet;

• Only one private well had groundwater samples collected that were above the ambient levels, but the concentrations at this well were significantly less than the IEPA groundwater standard;

• In the main areas of groundwater impacted by tritium (i.e., those where concentrations are above the groundwater standard) the tritium is more concentrated with depth. The cause of the vertical differences (over a small saturated interval of 20 feet) is believed to be caused by clean water recharge by precipitation. The depth to groundwater is at times less than 5 feet below the ground surface in the areas of tritium impacts and, as such, the upper water table will be flushed with clean precipitation recharge;

• Deeper private water supply wells downgradient of the main tritium impacts were sampled and found to have ambient concentrations of tritium. This supports the role of the regional aquitards (e.g., Wedron clayey till and the Scales Shale) as vertical barriers to deeper migration of tritium. In addition, the lack of any steep downward vertical hydraulic gradients in the shallow sand aquifer would minimize the vertical movement of tritium into the clay;

• Routine monitoring of select groundwater and surface water sample points since November 2005 has indicated stable or decreasing trends in tritium levels in the groundwater;

• The distribution of tritium in groundwater on the upgradient side (to the south) of the pond located north of Smiley Road and the distribution of tritium in groundwater downgradient, or north of the pond, indicates that the pond is acting to reduce the elevated concentrations of tritium discharging into it along Smiley Road.

This mixing and dilution is supported by tritium dating analyses performed by Dr. Robert Poreda of the University of Rochester. His analyses of Site data demonstrated that the pond is mixing on a seasonal basis and therefore is diluting the tritium that discharges from the south. In other words, the pond has played a significant role in preventing higher concentrations of tritium from migrating toward the north; and

• The groundwater flow and tritium migration varies across the Site and is expected to occur at a rate of 80 to 180 feet per year within the upper sand aquifer.

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Exelon is already moving forward with the next phases of work:

• Fill data gaps;

• Implement a groundwater monitoring program; and

• Begin remediation.

The remainder of this Section provides the reader with some of the details of Exelon's on-going efforts.

Remedial Action Plan Exelon has begun to develop interim and long-term remedial actions for the groundwater with tritium in excess of the groundwater standard. An Interim Remedial Action Plan (RAP) has been prepared to support short term actions that will prevent further migration of the tritium and will recover tritium from the main areas impacted.

This RAP has been submitted to the IEPA, the Office of the Attorney General, and the Will County State's Attorney.

Community Relations Plan Finally, as part of the ongoing private well sampling program, and in consultation with the IEPA, Exelon has developed a Community Relations Plan specific to the groundwater tritium issues at this Site. The Community Relations Plan was submitted to the IEPA on March 1, 2006. Exelon will implement this plan as well as continue its on-going coordination with the IEPA, the Nuclear Regulatory Commission (NRC), the Illinois Emergency Management Agency (IEMA), and the Illinois Department of Public Health (IDPH).

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1.0 INTRODUCTION

Conestoga-Rovers & Associates (CRA) has prepared this Focused Site Characterization Report (FSCR) for Exelon Generation Company, LLC (Exelon) to document findings with regard to the release of tritium into the groundwater at or in the vicinity of the Exelon Braidwood Nuclear Power Station (Braidwood Station) in Braceville, Illinois (refer to Figure 1.1). Tritium has been detected in the shallow sand aquifer at levels above the Illinois Environmental Protection Agency (IEPA) Groundwater Quality Standards (35 IAC 620 Section 410) in areas east of the main generating facility.

These releases originated at three vacuum breaker (VB) valve locations (VB-1, VB-2, and VB-3) located along the Cooling Lakes blowdown line. Since the spring of 2005, Exelon has undertaken extensive efforts to define and characterize these releases, including extensive sampling of groundwater, surface water, and public wells. As a result of these efforts, Exelon has defined the lateral and vertical extent of the tritium plume and is able to identify those areas both on site and off site where tritium levels exceed either the IEPA groundwater standard of 20,000 picocuries per liter (pCi/L) or the ambient concentration of 200 pCi/L.

Exelon has notified the IEPA, the Nuclear Regulatory Commission (NRC), the Illinois Emergency Management Agency (IEMA), and the Illinois Department of Public Health (IDPH) of the results and since the spring of 2005 has continuously communicated to them information on groundwater conditions. On December 16, 2005, the IEPA Bureau of Water issued a Violation Notice (VN) to Exelon due to the presence of tritium in groundwater. Exelon responded to this notice in a letter to the IEPA, dated February 2, 2006.

A second VN was issued February 27, 2006, and on March 2, 2006 Exelon met with the Attorney General's office, the Will County State's Attorney, the IEPA, and the IEMA to discuss the resolution of this matter. Those discussions are continuing.

The purpose of this report is to summarize for the IEPA and other interested agencies the sources, migration pathways, and extent of tritium in groundwater at the Braidwood Station Site. The only chemical of concern in this focused investigation is tritium.

However, Exelon has sampled and analyzed groundwater for all radionuclides potentially present and for inorganic parameters potentially associated with blowdown water, and tritium is the only constituent measured above its groundwater standard.

This report is considered the first step toward pursuing cleanup of tritium in the groundwater.

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This FSCR also presents the three dimensional nature of the tritium in groundwater which has migrated in the shallow sand aquifer and, as such, will form the basis of developing a Groundwater Management Zone (GMZ) pursuant to 35 IAC 620 Section 250.

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2.0 SITE DESCRIPTION 2.1 SITE LOCATION AND DEFINITION OF BOUNDARIES The Site, for the purposes of this FSCR, is defined as the areas of tritium-impacted groundwater resulting from past releases of blowdown line water to groundwater at vacuum breakers 1, 2, & 3. The Site therefore includes areas where tritium exceeds the groundwater standard and where it is detected above the ambient concentration (but below the groundwater standard). Refer to Figure 2.1 for the general Site boundaries.

As seen on Figure 2.1, the Site is located within the Exelon Generation - Braidwood Station property and on adjoining properties to the north. The Site is located near or adjacent to the municipal borders of the Villages of Braidwood, Braceville, and Godley on the southwestern tip of Will County in Illinois (Figure 1.1).

The area of investigation for this Site is bounded to the south by the Cooling Lake, to the northwest by Illinois State Highway 53, to the west by the access road to Braidwood Station, and to the east by Comet Drive/Cemetery Road.

As shown on Figure 2.1, vacuum breaker VB-1 is about 300 feet east of the Station access road and 50 feet south of the switchyard. VB-2 is approximately 3,000 feet to the east of VB-1 along the blowdown line, and VB-3 is approximately 600 feet to the northeast of VB-2 along the blowdown line (Figure 2.1).

2.2 OVERVIEW OF BRAIDWOOD STATION OPERATIONS Braidwood Generating Station is a two-unit nuclear generating facility capable of generating 1,120 net megawatts per unit. Units 1 and 2 are pressurized water reactors (PWRs) designed by Westinghouse and began commercial operation in July and October 1988, respectively. A PWR plant consists of three separate loops of fluids. Each loop is designed to avoid mixing the fluids of one loop with the fluids of another. The loops are called the primary loop, the secondary loop, and the tertiary loop.

The main purpose of the primary loop is to transfer the energy generated from fission in the fuel to the secondary loop steam generators. It is a closed loop system. Nuclear fission creates heat in the fuel. This heat is removed by the flow of reactor coolant water through the reactor vessel and into the steam generators. The heat is transferred to the secondary side where steam is generated. The water is then pumped back to the reactor vessel to cool the fuel again.

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The main purpose of the secondary loop is to use the steam generated in the steam generators to turn the turbine generator, which makes electricity. It is also a closed system.

The main purpose of the tertiary loop is to use cooler lake water to condense the steam in the condenser and transfer the heat to the atmosphere. This loop needs makeup water to operate properly. Makeup water comes from the Kankakee River.

As the steam is condensed in the condenser, the circulating water becomes hotter. The circulating water is discharged to the Cooling Lake where it loses some of its heat through evaporation. The now cooler water is then pumped backed to the condenser to start the loop over again.

2.3 SURROUNDING LAND USE Land surrounding the Site falls mainly into the agricultural, residential, and recreational use categories. Residential lots surround the Site to the north and to the east along Smiley Road and Center Street. Further to the north, there are several ponds or small lakes. The center of the Village of Braidwood is approximately 8,000 feet from the Site measured from Smiley Road. To the northwest of the Site, there are two main highways (Illinois State Highway 53 and Illinois Route 129) running parallel to each other with a railroad (Southern Pacific Railroad) between them. Within the southern portion of the Site is the Cooling Lake that is used as a recreational area in the summer for boating and fishing by the Illinois Department of Natural Resources (IDNR).

2.4 OVERVIEW OF GROUNDWATER USE IN THE SITE AREA The groundwater beneath Braidwood Station is not used as a potable resource for its operations. The Braidwood Station obtains all of its water requirements from the Kankakee River. There are a number of domestic wells near the Site (see Figure 2.2 for private well locations) that obtain their water from the underlying shallow sand aquifer, which comprises Quaternary age eolian and lacustrine sands to a depth of approximately 30 feet below ground surface. These sands overlie glacial drift (till) deposits that overlie bedrock. The glacial till ranges from clay to gravel but is predominantly clayey till. The groundwater within this shallow sand aquifer is under water table conditions with the depth to water ranging from 5 to 15 feet below the land surface. The shallow aquifer is recharged by precipitation and the groundwater within the shallow aquifer discharges to nearby surface streams and strip mines. The well 016841 (12) 4 CONESTOGA-ROVERS & ASSOCIATES

yields from the shallow aquifer, which range from 2 to 5 gallons per minute (gpm), are only suitable for domestic or farming purposes.

The Quaternary age deposits (shallow sand aquifer) are underlain by Pennsylvanian bedrock composed of siltstone, shale, sandstone, clay, limestone, and coal. The Pennsylvanian strata may locally yield up to 20 gpm from the interbedded sandstones.

The Cambrian-Ordovician aquifer is composed of a number of strata as outlined in Section 5.0. Water supply wells completed in this aquifer are at depths of over 600 feet.

The next major aquifer is the Mt. Simon, which is found at depths of over 1,400 feet.

Most of the groundwater supply wells within the surrounding area of the Braidwood Station are finished within these deeper aquifers (depths of 100 feet, and of 600 to 1,600 feet). There are a smaller number of water supply wells that are completed in the shallow sand aquifer. Further discussion on the Site geology, groundwater use, and groundwater supply wells is presented in Section 5.0. The Village of Braidwood, which is approximately 11/2 miles north of the Site, provides municipal water via at least one deep bedrock water supply well that has a depth of over 1,600 feet.

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3.0 BACKGROUND

INFORMATION ON THE RELEASES OF TRITIUM This section of the report provides information documenting the source of the tritium in the blowdown line, the operation of the blowdown line and the vacuum breaker valves, and the failures of these valves as they relate to groundwater impacts. The studies clearly show that the three vacuum breakers located just east of the main generation facility (VB-1, VB-2, and VB-3) are the source of the tritium. As such, these three vacuum breakers are considered to be the "Recognized Environmental Conditions", or "RECs", for the purpose of this Focused Site Characterization Report. The historical releases from each of these vacuum breakers are documented and discussed further in Sections 3.2 and 6.4. In addition, integrity testing of the blowdown line and groundwater studies near the blowdown line (refer to Section 6.4.1) have demonstrated that the pipe itself is not a REC and that the historical releases of water at the vacuum breakers fully explain the current distribution of tritium in the groundwater. The following discussions provide operational and historical information on the blowdown line and the vacuum breaker valves.

3.1 BLOWDOWN LINE OPERATION AND RADWASTE TANK DISCHARGES Braidwood Station employs a blowdown line to return water from the Cooling Lake back to the Kankakee River for the purposes of reducing the dissolved mineral concentration of the lake water (refer to Figure 1.1). This blowdown line also serves as a permitted discharge point for the Station's sewage treatment plant and the liquid radwaste system. Further details on the operation and normal discharges through the blowdown line are provided in the following sections.

3.1.1 BLOWDOWN LINE DESCRIPTION AND PURPOSE The blowdown line is constructed of a steel shell that is lined with concrete. The outside is covered with prestressed steel wire and concrete. The bell and spigot joints have a rubber gasket that seals the steel shells, and these joints are grouted inside and outside.

The pipe is designed to withstand an internal pressure of 110 pounds per square inch (psig) but the system normally operates below 20 psig. In addition to the vacuum breaker valve, there is an air-release valve that allows small amounts of air to be released from the line so that the larger vacuum breaker does not cycle to relieve this air (Figure 3.1).

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Braidwood Station uses a Cooling Lake to provide a heat sink for its main condensers.

Since the lake is warm and has a large surface area, it loses much of its water to evaporation. Evaporation of the water concentrates dissolved and suspended minerals in the lake. High concentrations of dissolved minerals, especially calcium carbonate, can result in calcium deposits on the Plant's heat exchangers, reducing their performance.

To reduce the concentration of dissolved minerals in the lake, Exelon discharges roughly 25,000 gpm of water to the Kankakee River through the blowdown line. Historically, flow rates were as low as 8,000 to 25,000 gpm. Exelon increased blowdown flow over the years to improve Cooling Lake chemistry. Approximately 48,000 gpm of water is pumped from the river to the lake, through the makeup line to compensate for losses due to evaporation and blowdown. The makeup line was installed parallel to the blowdown line.

Figure 1.1 presents a plan view of the blowdown line as it traverses from west to east across the Site, just north of the Cooling Lake. Figure 2.1 shows the location of the blowdown line and the makeup line in the Site area. Figure 3.1 presents a portion of the profile of the construction of the blowdown line (and makeup water line) and their placement in the subsurface.

3.

1.2 DESCRIPTION

OF THE VACUUM BREAKER VALVES The blowdown line is partly constructed of concrete, and it is not capable of withstanding any vacuum. Therefore, the pipe is fitted with 11 float-operated vacuum breaker valves. The makeup and blowdown lines are both fitted with vacuum breaker valves that allow air to escape as the lines are filled and allow air to enter the pipe when pressure and water levels in the pipe are low. The valves are 6-, 8-, or 10-inch nominal size and employ a stainless steel float to open and close the openings. Figure 3.1 presents a schematic of a typical vacuum breaker valve.

3.1.3 PERMITTED DISCHARGES FROM RADWASTE TANKS Excess plant water that contains tritium is periodically released via the blowdown line to the Kankakee River. This discharge meets federal requirements. IEPA NPDES Permit No. IL0048321 allows for liquid radwaste discharges to the blowdown line. In addition, as required in the NRC's regulations (10 CFR 20, 10 CFR 50, and 40 CFR 190), the Braidwood Station has developed an Offsite Dose Calculation Model (ODCM), which it uses to monitor and limit the radioactive effluents from the plant.

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3.

1.4 DESCRIPTION

OF THE SOURCE OF TRITIUM Under normal operating conditions at Braidwood Station, the principal radionuclide discharged from the plant is tritium. Tritium is formed when a neutron is captured by the boron and/or lithium in the coolant. Excess plant water that contains tritium is periodically released to the Kankakee River.

3.2 HISTORY OF VACUUM BREAKER RELEASES This section presents a description of the permitted liquid radwaste discharges to the blowdown line. This description is followed by a summary of the documented significant releases at each of the subject vacuum breakers (VB-1, VB-2, and VB-3). The scope of this report is limited to the tritium releases to the groundwater from vacuum breakers 1, 2, and 3.

The Liquid Radwaste Discharge Process Typically the station releases tritiated water every 3 days from the 25,000 gallon liquid radwaste tank. However, during outages there can be a release from the tank daily.

Prior to August of 2003, the typical flow rates in the blowdown line were 10,000 to 12,000 gpm. However, after 2003, the average flow rates were 20,000 to 25,000 gpm. The tritium concentration of water flowing within the blowdown line changes depending on whether there is a radwaste release tank being discharged at the time of the measurement. When no tritiated water is being discharged from the storage tank, the tritium concentration is that of the Cooling Lake, which is essentially ambient or background.

During a release, the concentration of tritium in the line will be significantly higher. The average tritium concentration during releases exceeds 1,000,000 pCi/L. 1 However, this is an average of water flowing in the blowdown line for only the period that the radwaste tank is actually discharging to the blowdown line, which typically ranges between 60 and 300 minutes. If a composite water sample were drawn by extracting a small continuous sample from the line (during a longer period when multiple radwaste tank releases occurred followed by periods of blowdown from the Cooling Lake), then 1 This average concentration is based upon a calculation performed by Exelon using records of releases from Braidwood Station, specifically, the blowdown line tritium concentration was derived using actual isotope and other release data collected from each release tank and the measured (or estimated) blowdown line flow rate. These records are available at the Braidwood Station.

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the composite concentration would be much less than 1,000,000 pCi/L and on the order of 40,000 to 100,000 pCi/L depending on the blowdown line flow. 2 Since the tritium concentration of the blowdown line varies, it is important to recognize that a continuous leak would have an average concentration equal to the composite concentration of the blowdown line during the time the leak was active. Conversely, a large leak from a vacuum breaker could happen during a release from the radwaste tank and not become well mixed before entering the ground. This could account for concentrations of tritium that exceeded the composite values. The remainder of this section provides a discussion on the history of leaks from VB-1, VB-2, and VB-3.

Vacuum Breaker 1:

On December 1, 1996, Exelon discovered a leak at VB-1. The leak was in the 1-inch pipe to the air release valve. The valve had last been inspected in June of 1995 at which time no leaks had been noticed. The line eventually broke and was repaired in June of 1997.

The volume of water that leaked was not recorded. However, Exelon estimated that the total leakage from VB-1 was between 120,000 to 380,000 gallons. Since the leak occurred over many weeks, this leak would have included liquid radwaste release water (containing tritium) in addition to the water from the Cooling Lake.

On November 20, 2000, Exelon discovered a leak when personnel noticed that water was flowing upward from the vacuum breaker pit through the manway cover and flooding the surrounding area. The responsible valve was repaired the next day. Exelon estimates that this leak was less than 4 million gallons. Sampling data indicate that this leak contained no tritium, suggesting that the leak likely occurred between releases from the radwaste tank.

On May 19, 2005, a leak at a rate of approximately 20 drops per minute was discovered at the pilot (air release) valve seat. The valve had been previously inspected in November 2004. The total leakage was to be estimated between 60 and 140 gallons. The repair was completed in October 2005. Again, the concentration of the tritium in the droplets is estimated to be a composite of flow in the line during 2005. Composite water (water in the pit) from the pilot valve leak identified in May 2005 was sampled and analyzed. The water sample contained 51,295 pCi/L of tritium. This was not, however, a sample of the groundwater, because the water was collected off of components within 2 This is based upon calculations made by Exelon using records from the Braidwood Station. Composite values were determined using the existing records and applying the rates to the duration of each leak.

Again, these records are available at the Braidwood Station.

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the valve pit and probably represented a composite of tritium levels within the blowdown line.

Vacuum Breaker 2:

In November 2000, a resident reported flooding of the ditch adjacent to Braidwood Station to the IEPA, which informed Braidwood Station. Exelon detected a leak from VB-2 as a result of vacuum breaker valve float failure that was repaired in December 2000. The Station pumped all standing water back into the blowdown line. This leak was caused by a water hammer, which broke the float in the valve, exposing an 8-inch opening. Exelon's analysis of their records 30 days prior to isolating this leak reveals:

• The average tritium concentration during releases was 1,305,000 pCi/L.

• The maximum tritium concentration in the pipeline during this period was 3,103,000 pCi/L. 3

• If a composite sample were drawn by extracting a small continuous sample from the line for the same 30-day period, the composite concentration would be roughly 91,400 pCi/L.

Vacuum Breaker 3:

In December 1998, there was a leak from VB-3 that was caused by a failed vacuum breaker float. This valve was found leaking due to flooding of the Smiley Road ditch on December 3, 1998. The valve was repaired on December 4, 1998. This valve was last inspected in December 1997, and no leakage was noted. The volume of the leak was not recorded, but was later estimated to be 3 million gallons over a 30-day period.

Exelon's records indicate that the historic releases and their estimated concentrations were:

• In 1998, the average blowdown line flow rate was 10,000 to 12,000 gallons per minute.

• In the 30 days prior to discovering the leak at VB-3, there were 24 releases from the radwaste tanks to the blowdown line.

• For the 30-day period prior to discovering the leak at VB-3, the average tritium concentration in the blow pipe was 624,000 pCi/L.3 3 It is important to note that by the time these releases discharge into the Kankakee River that the tritium levels are significantly below the Federal limits as noted in the ODCM.

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• The highest tritium concentration in the pipeline during this period was 1,852,000 pCi/L.3

• If a composite sample were drawn by extracting a small continuous sample from the line for the same 30-day period, the composite concentration would be 112,000 pCi/L.3 3.3 PREVIOUS GROUNDWATER STUDIES There are numerous studies of the local geology and groundwater. These studies provide a comprehensive understanding of the hydrogeologic conditions on the east side of the Braidwood Station. The remainder of this section presents a brief description of these previous studies. Additional findings are discussed in Section 5.0.

3.3.1 POWER PLANT DOCUMENTS - UFSAR REPORT During the construction of the Braidwood Station, a series of comprehensive investigations of regional and local geology and of surface water and groundwater conditions were conducted. These studies were performed for a number of purposes including geotechnical evaluations of the underlying geologic deposits, engineering designs for the slurry wall around the Cooling Lake, present and future sources of groundwater, present and future groundwater use, and other engineering and environmental purposes.

These studies are documented in the Updated Final Safety Analysis Report (UFSAR),

which was prepared by Sargent and Lundy (December 1988). Much of the current understanding of the geology and the groundwater conditions is based upon the information in the UFSAR.

3.3.2 2000 DIESEL FUEL RESPONSE On August 4, 2000, Exelon entered into the Illinois SRP in response to releases of diesel fuel from the west side of the main generating facility at the Braidwood Station on June 24, 2000. Beginning in 2001, Exelon initiated studies to address the conditions of soils, surface water, and groundwater on the northwest corner of the station. These studies determined the nature of flow in the shallow sand aquifer and its hydraulic relationship with the perimeter ditch that flows around the station from east to west.

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Exelon submitted a number of documents to the IEPA under the SRP for this diesel fuel release. On January 27, 2005, the IEPA issued a No Further Remediation (NFR) letter to Exelon for the diesel fuel release.

3.3.3 2005 INVESTIGATIONS OF TRITIUM IN GROUNDWATER AND SURFACE WATER In early spring of 2005, Exelon initiated investigations into the potential occurrence of tritium in water within the perimeter ditch (the drainage ditch that flows around the station). Initially, the studies were focused on the area west of the generating station (near the Village of Godley). Later, however, surface water samples collected upstream in the perimeter ditch and to the east of the Braidwood Station also found tritium above ambient concentrations. When elevated tritium was detected in the surface water at locations to the east, Exelon initiated a groundwater investigation based upon its experiences during the groundwater studies for the diesel fuel spill in 2000 4 .

In the spring of 2005, Exelon initiated a groundwater monitoring program to determine the source and extent of tritium in the perimeter ditch and in the shallow groundwater on the east side of the Station. In the fall of 2005, groundwater samples collected at the northern property line (near Smiley Road) contained elevated levels of tritium that exceeded background levels (200 pCi/L), but were well below the Illinois groundwater standard of 20,000 pCi/L. After obtaining these results, Exelon took additional steps to investigate the source of the tritium and its extent in the groundwater. It installed monitoring wells at its northern property boundary and other wells downgradient of the most likely sources of the tritium (vacuum breakers).

In November 2005, Exelon undertook other studies to determine:

• the sources of the tritium in the groundwater;

• the lateral and vertical extent of the tritium in groundwater on and off the property; and

• when the releases had occurred and whether releases were still continuing.

4 In October 2000, in response to a release of water from VB-2, Exelon installed four shallow monitoring wells (MW-101 to MW-104) in order to determine the direction and rate of groundwater flow near of VB-2.

016841 (12) 12 CONESTOGA-ROVERS & ASSOCIATES

These studies continued through February 2006 and form the basis of this FSCR and of the current understanding of the nature and extent of tritium in the groundwater at the Site.

At the time of this report approximately 300 groundwater samples and surface water samples were collected from permanent monitoring wells, temporary wells, ponds, ditches, and private residence wells. In the area downgradient from VB-1, VB-2, and VB-3, Exelon has sampled 15 private residence wells. Many of the domestic wells are being sampled routinely.

3.4 CURRENT REGULATORY STATUS Braidwood Station is subject to a number of regulatory permits and notices. The remainder of this section discusses the primary permits.

3.4.1 NPDES AND NRC PERMITS FOR THE BLOWDOWN LINE The blowdown line and the Cooling Lake water makeup line transverse the Site area in the south. The blowdown line is subject to regulation under the IEPA NPDES Permit (IL0048321) and the Braidwood Station ODCM. The NPDES permit provides limits on parameters such as pH, Total Suspended Solids, BOD5, Oil and Grease, Total Residual Chlorine, Total Residual Oxidant, and temperature. The permit also requires monitoring of parameters such as blowdown discharge flow. The ODCM is the document required in the NRC's regulations (10 CFR 20, 10 CFR 50, and 40 CFR 190) to monitor and limit the radioactive effluents from the plant. The ODCM places limits on concentrations of radioactive effluents released and requires monitoring of the concentrations of these effluents.

3.4.2 DECEMBER 2005 VIOLATION NOTICE In a letter dated December 16, 2005, Exelon received a Violation Notice from the IEPA Bureau of Water. This letter was a response to the tritium that exceeded the 35 IAC 620 groundwater standard (20,000 pCi/L).

Exelon responded to the December 16th Violation Notice in a letter, dated February 2, 2006. In their February 2nd letter, Exelon committed to entering the IEPA SRP and to 016841 (12) 13 CONESTOGA-ROVERS & ASSOCIATES

preparing this Focused Site Characterization Report. The February 2nd letter also contains a schedule to develop deliverables and plans required under the SRP with the goal of remediating the Site and obtaining an NFR letter. The IEPA's December 16, 2005 Violation Notice letter and Exelon's February 2, 2006 response letter are in Appendix A.

On February 17, 2006, Exelon met with the IEPA to discuss the VN and Exelon's plans to remediate the tritium. On March 2, 2006, Exelon met with the IEPA, the IEMA, the Office of the Attorney General, and the Will County State's Attorney to discuss this matter. As part of this process, Exelon has prepared the FSCR for submittal to the IEPA, the Office of the Attorney General, and the Will County State's Attorney.

3.4.3 REGULATORY AGENCY COORDINATION Since the Spring of 2005, when the surface water in the perimeter ditch was found to contain tritium, Exelon has regularly communicated with these agencies:

• IEMA;

• IDPH;

• NRC;

• IEPA Bureau of Water; and

• Office of the Illinois Attorney General.

In addition, Exelon has been providing these agencies regular updates of investigative plans, the status of sampling programs, and preliminary analytical data. Both the preliminary and final analytical results of all groundwater analyses have been provided to the IEMA and to the NRC as soon as they are available. In addition, since November 2005, Exelon has attended the following meetings :

• December 20, 2005 with the IEPA, IEMA, NRC, and IDPH in Springfield to discuss the current understanding of the source of the tritium, the known extent of the tritium, and the future sampling program;

• January 23, 2006 with the IEPA, IEMA, NRC, and IDPH in Springfield to discuss recent findings and the proposed response and actions to be taken with respect to the Notice of Violation;

• February 17, 2006 meeting with the IEPA to discuss the compliance commitment agreement; and

• March 2, 2006 meeting at the Attorney General's office.

016841 (12) 14 CONESTOGA-ROVERS & ASSOCIATES

Exelon has also had a number of meetings with local property owners and area residents. Exelon has developed a Community Relations Plan, and this has been provided to the IEPA under separate cover (March 1, 2006). As part of this plan, Exelon held an open house information forum on February 28, 2006 at the Exelon Training Center along Essex Road. This forum was open to all interested members of the public.

016841 (12) 15 CONESTOGA-ROVERS & ASSOCIATES

4.0 SITE-SPECIFIC SAMPLING PLAN -

GROUNDWATER INVESTIGATION OF TRITIUM 4.1 PURPOSE AND SEQUENCE OF INVESTIGATIONS The investigations of tritium in groundwater at the Braidwood Station began in early Spring of 2005. 5 The initial investigation included drilling and sampling permanent wells around each of the three subject vacuum breakers (VB-1, VB-2, and VB-3) to determine groundwater flow directions and the concentration of tritium in the groundwater. Based upon the results from the monitoring wells installed in July 2005 (MW-105 to MW-109), additional monitoring wells were installed in September 2005 downgradient (to the north) of the vacuum breakers and at the Braidwood Station property line (MW-110 to MW-113) to determine if tritium above the ambient concentration was migrating off Site.

The analytical results from monitoring wells at the property line, specifically the tritium concentrations in MW-113 (the initial sample collected October 19, 2005 had a tritium result of 4,480 pCi/L), lead to the development of an aggressive investigation program and an Exelon Task Force to address the presence of tritium on and off the Braidwood Station property. This program consisted of the installation and sampling of temporary wells that were installed at shallow and deeper depths within the upper sand aquifer between November 2005 and February 2006. The goals of the aggressive investigative program were to determine :

• the source of the tritium;

• the lateral and vertical extent of the tritium in groundwater on and off site; and

• when the releases had occurred and whether releases were still continuing.

This section of the report provides an overview of the field studies completed from 2005 to the time this report. This section includes the number, location, type, and methods of sample collection.

Figure 4.1 presents the location of all groundwater monitoring points (temporary wells and permanent wells). Figure 4.2 presents the locations of surface water bodies sampled and monitored, including the perimeter ditch and off-property ponds. Figure 2.2 presents the locations and identifiers of private wells sampled as part of the investigations in the area north of Smiley Road.

5 Groundwater flow was determined in an area near VB-2 during an investigation of the leak from this vacuum breaker in November 2000.

016841 (12) 16 CONESTOGA-ROVERS & ASSOCIATES

4.2 FIELD STUDIES COMPLETED TO DATE CRA retained Terra-Trace Environmental Services (Terra-Trace) of Lake Bluff, Illinois to install the temporary wells, Altech Services, LLC (Altech) of Livonia, Michigan to install the permanent wells, and Boart Longyear Company (Boart) of Schofield, Wisconsin to install the recovery wells. Drilling investigations began in July 2005 and were completed in February 2006. A total of 156 wells consisting of 143 temporary wells, 9 permanent wells, and four recovery wells, were installed at the Site during this time period (four permanent wells had been installed previously in 2000). Figure 4.1 presents groundwater monitoring locations. Figure 4.2 presents surface water monitoring locations. Table 4.1 presents monitoring wells specifications.

Three staff gauges (SG-A, SG-B, and SG-C) were installed in three ponds located north of Smiley Road. Surface water samples were collected from these ponds and the perimeter ditch.

Single well aquifer testing was conducted at four permanent wells on October 20, 2005 and at two temporary wells on February 2, 2006.

The sections below outline a brief discussion of the field activities performed and work completed to date. Appendix B provides a complete discussion of the methods used to perform the field activities.

4.2.1 PERMANENT MONITORING WELL INSTALLATION CRA oversaw the installation of four permanent monitoring wells (MW-101 through MW-104) at the Site in November 2000 to determine the direction of groundwater flow.

Five permanent monitoring wells (MW-105 through MW-109) were installed on July 26 and 27, 2005 for groundwater flow and tritium analyses. Four permanent monitoring wells (MW-110 through MW-113) were later installed on September 18, 2005 as part of the tritium investigation. All wells except for MW-110 were advanced to 16 feet below ground surface (bgs). MW-110 was advanced to 20 feet bgs. The monitoring wells were installed so that the well screen straddled the water table at depths of 15 to 20 feet bgs.

Subsequent sampling of deeper wells indicated a need to install permanent and temporary monitoring wells deeper and to the bottom of the sand zone (25 to 30 feet 016841 (12) 17 CONESTOGA-ROVERS & ASSOCIATES

bgs). Monitoring wells MW-105D, MW-106D, MW-111D, MW-112D, and MW-113D were installed during December 2005 and January 2006 to depths of 24 to 27 feet bgs.

Well completion forms and stratigraphic logs are in Appendix C.

4.2.2 PERMANENT MONITORING WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the permanent wells were developed.

4.2.3 TEMPORARY MONITORING WELL INSTALLATION Beginning in November 2005 and extending through February 2006, 216 shallow and deep temporary wells were installed using direct push (Geoprobe) methods. The use of the Geoprobe drilling technique and the installation of temporary 1-inch diameter monitoring wells allowed easy and fast collection of groundwater levels and groundwater samples for tritium analyses. Shallow wells range in depth from 11 to 21 feet bgs. Deep wells range in depth from 21 to 41 feet bgs. Deep wells were installed to the top of the underlying clay layer, the location of which was determined at each location in one of two ways. The top of the clay layer was identified by using a Geoprobe macrocore and visually looking at the soil sample retrieved in the macrocore or by a noticeable change in resistance encountered by the Geoprobe as noted by the Geoprobe operator.

Well completion forms and stratigraphic logs are in Appendix C.

4.2.4 TEMPORARY MONITORING WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the temporary wells were developed.

4.2.5 INSTALLATION OF RECOVERY WELLS In anticipation of possible hydraulic control or tritium recovery actions, four recovery wells (RW-1 through RW-4) were installed on December 1 and 2, 2005 as a contingency.

The recovery wells were advanced to reach the top of the underlying clay layer, between 24 to 28 feet bgs.

016841 (12) 18 CONESTOGA-ROVERS & ASSOCIATES

Well completion forms and stratigraphic logs are in Appendix C.

4.2.6 RECOVERY WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the recovery wells were developed.

4.2.7 GROUNDWATER AND SURFACE WATER LEVEL MEASUREMENTS The depth to water in each well was measured to the nearest 0.01 foot using an electronic water level meter. Measurements were recorded after each well installation and at each sampling event. Surface water level measurements were recorded by reading the staff gauges (SG-A, SG-B, and SG-C). Currently, water levels at the staff gauges are read on a routine basis.

The water level data are presented in Table 4.2.

4.2.8 GROUNDWATER SAMPLING AND ANALYSES A total of 13 permanent, 143 temporary, and four recovery wells were sampled during this investigation. All 160 permanent, temporary, and recovery wells were sampled and analyzed for tritium in the Site area. In addition, two samples (RW-1 and RW-2) were analyzed for total metals and general chemistry. Twenty-four samples (BL-01 through BL-08, BL-10 through BL-16, BL-10D through BL-17D) were analyzed for sodium and chloride. The sodium and chloride were analyzed at these sampling points located along the blowdown line based on general chemistry sample analyses for the blowdown line. Two samples of water in the blowdown line itself and two background wells were sampled and analyzed for a full suite of general chemistry parameters. These samples were collected to look for indication of leaks within the blowdown line. Refer to Section 6.2 for further discussion. In addition, samples were also analyzed for other radioisotopes present in the liquid radwaste discharges (refer to Section 4.2.8.1).

Groundwater samples collected for tritium analyses were delivered to an Exelon representative, who submitted them to Environmental, Inc. of Northbrook, Illinois, to the IEMA, and to the NRC for analyses. Groundwater samples collected for total metals, general chemistry, sodium and chloride analyses were hand delivered to First 016841 (12) 19 CONESTOGA-ROVERS & ASSOCIATES

Environmental Laboratories, Inc. (First Environmental) of Naperville, Illinois. Results of tritium analyses and of other radioisotopes analyses are in Appendix D. This appendix includes copies of laboratory reports from Environmental, Inc., and these are presented on a CD.

To better evaluate the potential for past leaks or on-going leaks from the vacuum breakers and from the blowdown line, the general chemistry of the water flowing in the blowdown line was analyzed. Samples from the blowdown line and from representative groundwater monitoring locations were analyzed for a set of typical groundwater quality parameters (e.g., anions, cations, metals, etc.) by First Environmental. These samples were used to develop a list of indicator parameters (excluding tritium) for water flowing in the line. These analytical results are discussed in Section 6.2.

The quality assurance procedures and protocols used by Environmental, Inc. for the tritium analyses and for the other radioisotopes are in Appendix E. Environmental, Inc.

is the only independent laboratory certified by the State of Illinois to conduct radiological testing of groundwater.

Monitoring wells were purged prior to sample collection (see Table 4.3 for purging parameters). Groundwater samples were collected in accordance with the CRA Slow Purging/Minimal Disturbance Protocols specified in Appendix B. The CRA procedures were further expanded to address the requirements of Exelon, Environmental, Inc., and Site conditions. The CRA procedures were supplemented with Exelons protocols as specified in Appendix B.

4.2.8.1 OTHER RADIOISOTOPE ANALYSIS OF GROUNDWATER In addition to the sampling and analysis of the groundwater for tritium, the primary radioisotope discharged to the blowdown line from the liquid radwaste tank, Exelon also analyzed for other radioisotopes. The initial set of groundwater samples collected from the monitoring points were also analyzed for a specific set of radioisotopes that were present in the liquid radwaste tank, but at much lower concentrations than tritium.

This included sample analysis by Environmental, Inc. for parameters such as Cobalt-58, Cesium-134, and others. Appendix D provides the results from these specific radioisotope analyses. In the Site area, over 150 groundwater samples were submitted to Environmental, Inc. for these specific radioisotope analyses.

016841 (12) 20 CONESTOGA-ROVERS & ASSOCIATES

4.2.9 SURFACE WATER SAMPLING Surface water samples were collected at several locations beginning in November 2005.

On November 30, 2005, two surface samples were collected from the pond located at Center Street and Smiley Road (surface water locations SW-1 and SW-2). On December 2, 2005, two surface samples were collected from Fatlan Pond, located west of Center Street (locations SW-3 and SW-4). Surface water location SW-2 was sampled again on January 11, 18, and 25, 2006, and February 1, 2006. One surface water sample was collected from Zimmer Pond, located west of Comet Drive (location SW-5), on January 30, 2006. Surface sample PW-6P was collected from Scamen Pond on February 9, 2006. A surface sample was taken from Fatlan Pond on February 9, 2006.

Currently, surface location SW-2 is being sampled on a weekly basis. Figure 4.2 provides surface water sampling locations.

4.2.10 PRIVATE WATER WELL SAMPLING PROGRAMS Exelon initiated sampling of nearby private wells in November 2005. Since the initial samples collected on November 30, 2005, a routine program has been developed and implemented by CRA. This routine private well sampling program applies to 15 locations (residences) found north of Smiley Road and downgradient of the impacted groundwater areas (see Figure 2.2).

4.2.11 SINGLE WELL AQUIFER TESTING Single well hydraulic response tests were performed on site on October 20, 2005 on four permanent wells (MW-105, MW-107, MW-109, and MW-112). Single well hydraulic response tests were performed off site on February 2, 2006 on two temporary wells (P-2 and G-2). The response tests were performed in order to determine the hydraulic conductivity of the aquifer in these areas. The tests were performed using rising head methods, wherein the water level in a monitoring well is depressed and water level recovery is monitored over time. A pressure transducer and data logger monitored water levels. Data obtained from the single well response tests was evaluated using the methods developed by Bouwer & Rice (1976).

The geometric mean for the test results from October 20, 2005 indicate a site-specific hydraulic conductivity of 2.5 x 10-2 cm/sec. The geometric mean for the test results from February 2, 2006 indicate a site-specific hydraulic conductivity of 3.7 x 10-2 cm/sec.

Hydraulic conductivity analyses are in Appendix F.

016841 (12) 21 CONESTOGA-ROVERS & ASSOCIATES

4.3 AREA WIDE WATER WELL INVENTORY CRA collected a water well inventory from the Illinois State Water Surveys Private Well Database and Public, Industrial, Commercial Survey (PICS) Database in November 2005, December 2005, and January 2006. The well inventory was collected for the area one mile north and one mile south of Smiley Road and one mile north and one mile south of the blowdown line for the area east of vacuum breaker VB-4 to the Kankakee River. The Private Well and PICS Database queries well records by county, township, range, and section.

The search included records from Will County, Township 32N, Range 9E and Sections 13 to 17, 20 to 24, and Range 10E Sections 18 and 19. The inventory produced 429 records total; 46 of these records (see Table 4.4) are downgradient (north) of the Site.

The water well inventory provides information about the water well owner, driller, drill date, depth, and if available address, well type, aquifer type, static water level, and pump level. A collection of findings from the well inventory is in Appendix G.

4.4 REGIONAL HYDROGEOLOGIC DATA COLLECTION As part of the characterization of Site conditions, CRA requested regional hydrogeologic data from the Illinois State Geological Survey (ISGS) and the Illinois State Water Survey (ISWS). Some of this information has not yet been received but will be incorporated into future evaluations.

4.5 SAMPLING AND ANALYSIS RELATED TO TRITIUM DATING Exelon retained Dr. Robert Poreda of the University of Rochester to evaluate the age of the tritium found in the groundwater at the Site. The main purpose of the tritium dating analysis was to evaluate whether there was any indication of an active leak from the vacuum breakers or from the blowdown line. In addition, the results of the tritium dating analysis was used to confirm the conceptual site model presented in Section 6.0.

Dr. Poreda accompanied CRA to the Site on December 22, 2005 and collected groundwater samples for his analyses from 14 groundwater monitoring locations across the Site. These samples were collected from wells completed in the shallow and in the deep groundwater zone. In addition, the samples were collected across the tritium 016841 (12) 22 CONESTOGA-ROVERS & ASSOCIATES

impacted area. Groundwater was purged from temporary and permanent monitoring wells with the same procedures used for characterization sampling. However, Dr. Poreda also employed specific sample collection and containerization processes that are designed to minimize helium diffusion. The samples were then sent to the University of Rochester laboratory for specialty laboratory analyses. Further discussion on the sampling techniques, laboratory analyses methods, and the results of Dr. Poredas studies are in Appendix H. This appendix also provides background information and other references on the dating evaluation process.

016841 (12) 23 CONESTOGA-ROVERS & ASSOCIATES

5.0 DOCUMENTATION OF FIELD ACTIVITIES -

PRESENTATION OF STUDIES AND ANALYSES COMPLETED TO DATE This section provides a summary of regional and Site-specific geology and hydrogeology along with a discussion of vertical hydraulic gradients, groundwater elevations and flow directions, and overburden aquifer hydraulic conductivity in the Site area.

5.1 PHYSICAL SITE SETTING This section provides an overview of the surface and subsurface features of the Site area.

Discussions on regional and local hydrogeology are provided.

5.1.1 REGIONAL TOPOGRAPHY AND SURFACE WATER FEATURES The site is located within the Kankakee River Basin approximately ten miles from the confluence of the Kankakee River with the Illinois River (Figure 1.1). In general, the topography of the area slopes downward to the north toward the Illinois River.

5.1.2 REGIONAL GEOLOGY The regional geology is composed of a relatively thin overburden layer overlying the bedrock (see Figure 5.1). The overburden consists of a sand and gravel unit and a glacial till unit with some lenses of coarse-grained glacial drift. The important bedrock units can be divided into five general sections:

• Pennsylvanian age siltstone, shale, and coal;

• Silurian dolostone;

• Ordovician shale;

• Ordovician-Cambrian sandstone and limestone/dolostone; and

• Cambrian Eau Claire shale.

The Pennsylvanian age units are generally horizontal strata that act as an aquitard. The coal-bearing Carbondale Formation (Colchester Member) within this group was previously strip-mined in the area of the Site. The strip mining removed the overlying units to the bottom of this coal seam.

016841 (12) 24 CONESTOGA-ROVERS & ASSOCIATES

Beneath the Pennsylvanian siltstone and shale aquitard lies a Silurian-age dolostone aquifer. The Ordovician shale of the Maquoketa Shale Group separates this dolostone aquifer from the underlying Cambrian-Ordovician aquifers. The Maquoketa Shale Group consists of several shale and limestone units that act as an aquitard between the two bedrock aquifers.

The Cambrian-Ordovician aquifers beneath the Maquoketa Shale Group consist of two major sandstone aquifers, the Ancell aquifer (composed of the Glenwood Formation and St. Peter Sandstone) and the Ironton-Galesville aquifer (composed of the Ironton and Galesville Sandstones). Separating these two aquifers is a confining unit made up mainly of dolomite and shale with some sandstone. In general, these two units are considered to be one aquifer and are called the deep bedrock aquifer. The deep bedrock aquifer is an average thickness of 1000 feet and dips to the southeast (Visocky, 1985).

The Cambrian-age Eau Claire Formation acts as an aquitard that separates the deep bedrock aquifer from the Mt. Simon aquifer. The Mt. Simon Sandstone is not suitable for groundwater extraction due to poor water quality (Visocky, 1997).

5.1.3 REGIONAL HYDROGEOLOGY Groundwater in the region is mainly extracted from three aquifers:

• The sand and gravel overburden deposits;

• The shallow Silurian dolomite; and

• The deep sandstone and dolomite formations of Cambrian and Ordovician age.

There are several private wells screened within the surficial sand unit where well yields are highly variable. In general, yields range from 20 gpm to 100 gpm; the higher yields are in areas where the sand and gravel deposits are thickest. The recorded well yields in the Silurian-age dolostone aquifer are extremely variable, with yields over 1,000 gpm measured. In general, yields of less than 500 gpm are encountered most often (Schicht et al, 1976).

The most important aquifer in the region is the Cambrian-Ordovician Aquifer, which is also called the deep sandstone aquifer. The wells from this aquifer yield approximately 700 gpm. Figure 5.2 presents the groundwater elevations and regional groundwater flow direction in the bedrock aquifer. As shown, the groundwater in the region flows 016841 (12) 25 CONESTOGA-ROVERS & ASSOCIATES

toward Lake Michigan. Near the Site, this means that the regional groundwater flow in the deep bedrock aquifer is to the north-northeast (Schicht et al, 1976).

5.1.4 SITE-SPECIFIC TOPOGRAPHY AND SURFACE WATER FEATURES Figure 2.1 presents the relevant surface water features at the Site. The topography at the Site is generally flat, with a gentle slope to the north. Surface water drains toward the Exelon and northwest ponds, as well as toward the perimeter ditch.

5.1.5 SITE-SPECIFIC GEOLOGY The geology beneath the Site consists of a relatively thin overburden deposit that overlies alternating layers of shale/siltstone and dolostone. Figure 5.3 presents a generalized south-north geologic cross-section of the Site, and provides a general overview of the important lithologies of the subsurface.

The overburden at the Site consists of the Equality Formation (silty sand) and the Wedron Formation (glacial outwash and till). The Equality sand is the surficial unit and is described as a homogenous, loose, gray to brown sand in borehole logs completed at the Site. This formation is approximately 20 feet thick at the Site. The Wedron Formation consists of glacial till and interbedded discontinuous glacial outwash deposits. At the Site the Wedron Formation ranges from 15 to 20 feet thick. Figure 5.4 presents the top of the clay/till unit at the Site, which overlies the bedrock. The figure indicates that the clay unit generally dips to the north, generally following the overburden groundwater flow direction at the Site.

The bedrock at the Site is generally typical of the regional geology, with the exception that the Silurian dolostones are not present. The upper bedrock at the Site is encountered at approximately 40 feet below ground surface and consists of Pennsylvanian siltstone, shale, limestone and coal with a local water-bearing conglomerate. Strip mining south of the Site has removed the coal and the overlying units. The mined area has subsequently filled with water and is now a lake. The important features of the deeper stratigraphic units were presented in Section 5.1.2 and 5.1.3.

016841 (12) 26 CONESTOGA-ROVERS & ASSOCIATES

5.1.6 SITE-SPECIFIC HYDROGEOLOGY In general, there are two aquifers used for water supply near the Site. The first aquifer consists of the sand in the overburden, and the second aquifer is the Ordivician-Cambrian sandstone units of the deep bedrock aquifer.

The groundwater in the sand aquifer of the overburden occurs under unconfined (water table) conditions and ranges in thickness from 20 to 22 feet. The groundwater in this aquifer is recharged by local precipitation and discharges to local ponds and streams, and to the bedrock. Water well yields from this aquifer are suitable for domestic use, and range from 2 to 5 gpm (UFSAR, December 1988).

Over 155 monitoring wells have been installed into the deep and shallow zones of the overburden aquifer at the Site. Figure 4.1 presents the monitoring well network.

Several well nests have been installed in the overburden aquifer not only to determine the vertical distribution of impacted groundwater, but also the vertical hydraulic gradient within the aquifer. The calculated vertical hydraulic gradients at the Site are presented on Figure 5.5 and in Table 5.1. These data indicate that there is no systematic pattern of vertical hydraulic gradient at the Site.

Table 4.2 presents groundwater elevations. Figures 5.6 and 5.7 present the groundwater elevations and flow directions in the shallow and deep zones, respectively. The figures show that groundwater at the Site flows generally north-northwest in both zones of the aquifer. 6 The pattern of groundwater contours and the elevation of the water in Exelon Pond indicate that there is a significant interaction between the groundwater in the overburden and the water in the pond. Groundwater elevations south (upgradient) of the pond are higher than the pond elevation, indicating that groundwater discharges to the pond. The groundwater elevations measured north (downgradient) of the pond are lower than the pond level, indicating that surface water recharges the groundwater to the north. This has important implications for contaminant transport at the Site, because it indicates that impacted groundwater discharges to the pond, become mixed with unimpacted surface runoff, and then recharges to the groundwater at a significantly lower concentration.

The results from single-well response tests indicate that the hydraulic conductivity of the overburden aquifer is in the range of 2.5x10-2 cm/sec to 3.7x10-2 cm/sec (see Appendix F). The average horizontal hydraulic gradient in the overburden is 0.002.

6 The groundwater elevation near MW-106 is probably elevated beyond its normal level due to localized mounding caused by nearby ditches and the Cooling Lake.

016841 (12) 27 CONESTOGA-ROVERS & ASSOCIATES

Assuming an effective porosity of 0.3, average groundwater velocity in the overburden aquifer is 80 ft/yr. to 170 ft/yr. The shallow aquifer flow is more influenced by the recharge and surface water features at the Site, and therefore has the higher groundwater velocity; the deeper groundwater velocity is closer to the lower end of the range of values.

The Braidwood Station Cooling Lake, which is located on the upgradient side of the Site, is not in direct contact with the upper sand aquifer, but rather is separated by a slurry wall that was installed at the time the Braidwood Station was built. The slurry wall was installed into the Wedron clayey till unit. The Cooling Lake is surrounded by this slurry wall and is, therefore, isolated from the upper sand aquifer in all areas of the Braidwood Station property.

The overburden aquifer is separated from the deep bedrock aquifer by approximately 140 feet of relatively impermeable shales. The shale units act as aquitards, limiting the hydraulic communication between the groundwater in the overburden and the bedrock aquifer. Most domestic wells in the area are completed within the Glenwood-St. Peter Formation, which is approximately 600 feet below the ground surface.

As mentioned in Section 5.1.2, there is a history of open-pit coal mining in the region.

As a result of coal mining, there are several small lakes near the Site formed when abandoned open-pit mines subsequently filled with groundwater and precipitation. The Cooling Lake south of the facility is one of these lakes. Historical documents indicate the potential for abandoned mine shafts near the Site. In addition, a hand sketch provided by an adjacent landowner indicates the presence of a mine shaft and air shaft in property north of Smiley Road (see Appendix I). It is possible that these abandoned shafts could act as conduits for impacted water to infiltrate into the water-bearing units immediately underlying the Wedron till (Carbondale Channel Sandstone) and immediately overlying the coal seam (Carbondale conglomerate). The coal seams are found at depths of approximately 100 feet bgs. All of the currently available relevant information regarding mining shafts in the area is in Appendix I. Further evaluations of the influence of these historical mining operations on shallow groundwater is presented in Section 6.4.

016841 (12) 28 CONESTOGA-ROVERS & ASSOCIATES

6.0 DESCRIPTION

OF THE CHEMICALS OF CONCERN AND SOURCE AREAS This section presents an evaluation of the source of tritium, its fate in the subsurface, and its distribution in groundwater.

6.1 GENERAL TRITIUM CHARACTERISTICS Tritium (chemical symbol 3H ) is a radioactive isotope of the element hydrogen. Tritium is produced naturally in the upper atmosphere when cosmic rays strike air molecules.

Tritium is also produced during nuclear weapons explosions, as a byproduct in reactors producing electricity, and in special production reactors, where the isotopes lithium-7 and/or boron-10 are bombarded to produce tritium.

Although tritium can be a gas, its most common form is in water because, like non-radioactive hydrogen, radioactive tritium reacts with oxygen to form water.

Tritium replaces one of the stable hydrogen atoms in the water molecule and is called tritiated water. Like H2O, tritiated water is colorless and odorless. Tritiated water behaves chemically and physically like non-tritiated water in the subsurface, and therefore a plume of tritiated water will travel at the same velocity as the average groundwater velocity.

Tritium has a half-life of approximately 12.3 years. It decays spontaneously to helium-3 (3He). This radioactive decay releases a beta particle (high-energy electron). The radioactivity of tritium is the source of the risk of exposure. The United States Environmental Protection Agency (USEPA) has established a Maximum Contaminant Level (MCL) of 4 millirem per year for beta particles and photon radioactivity from man-made radionuclides in groundwater. This standard applies to public water supplies (40 CFR 141.1). The average concentration of tritium that is assumed to yield 4 millirem per year is 20,000 pCi/L. If other radionuclides that emit beta particles and photon radioactivitiy are present in addition to tritium, the sum of the annual dose from all the radionuclides shall not exceed 4 millirem/year.

Tritium is one of the least dangerous radionuclides because it emits very weak radiation and leaves the body relatively quickly. Since tritium is almost always found as water, it goes directly into soft tissues and organs. The associated dose to these tissues is generally uniform and is dependent on the water content of the specific tissue.

Under normal operating conditions at the Braidwood Facility, tritium is the principal radionuclide discharged from the plant. Tritium is formed when boron and/or lithium 016841 (12) 29 CONESTOGA-ROVERS & ASSOCIATES

atoms present in the reactor coolant capture a neutron. Exelon periodically releases excess plant water that contains tritium to the Kankakee River through the blowdown line.

Tritium in the groundwater at the Site therefore has two sources: tritium in infiltrating precipitation (background) and tritium from leaks from the vacuum breakers in the blowdown line. Background tritium concentrations in groundwater is roughly 200 pCi/L. These background values are discussed in more detail in Section 7.0.

6.2 CHARACTERISTICS OF WATER IN THE BLOWDOWN LINE - COOLING LAKE WATER QUALITY Braidwood generating station uses a cooling lake to provide a heat sink for its main condensers. Since the lake is warm and has a large surface area (over 2,800 acres), it loses much of its water to evaporation. This evaporation causes the concentration of dissolved and suspended minerals in the lake to increase.

Table 6.1 presents a comparison of the general chemistry of cooling water samples and samples from unimpacted groundwater wells. Appendix J presents the laboratory reports for these analyses. CRA compared Cooling Lake (blowdown line) samples at the facility and at the outfall to the Kankakee River to groundwater samples collected from MW-106D and MW-110. As shown in Table 6.1, the chemistry of the cooling water is generally consistent. More specifically, the concentrations of both chloride and sodium in the cooling water are significantly higher than in the groundwater samples. There are differences in the concentrations of other parameters between the cooling water and the groundwater, but the most significant differences are the chloride and sodium concentrations. Therefore, CRA used sodium and chloride as indicators of cooling water impact to the groundwater in the absence of tritium values. These data also show that the concentrations of metals and general chemistry parameters in the cooling water do not exceed applicable groundwater standards.

In addition to tritium and general chemistry sampling, Exelon has sampled the groundwater at monitoring wells for other radionucleides. These data are in Appendix D. The results indicate that none of the radionucleides exceeded the lower limit detection in groundwater. Therefore, the only contaminant of concern in the groundwater at the Site is tritium.

016841 (12) 30 CONESTOGA-ROVERS & ASSOCIATES

6.3 DISTRIBUTION OF TRITIUM IN GROUNDWATER AT THE SITE Figures 6.1 and 6.2 present the estimated horizontal distribution of tritium in the shallow and deep overburden zones, respectively. The figures show that the highest tritium concentrations are near VB-2 and VB-3, supporting the conclusion that these two vacuum breakers are the source of the tritium. The groundwater plume extends north and west from this area toward Exelon Pond. As the figures clearly show, concentration northwest of the pond is considerably lower. This indicates the plume is being diluted by the pond.

There is a smaller source near VB-1, which is immediately east of the facility. As shown on Figures 6.1 and 6.2, tritium concentrations in this area are much lower than in the area north of VB-2 and VB-3. The concentrations of tritium decrease quickly to background levels downgradient of VB-1.

Figures 6.1 and 6.2 indicate that tritium concentrations are somewhat higher in the deep zone relative to the shallow zone. This is attributed to precipitation infiltration. After the impacted groundwater begins to migrate away from the source area, infiltrating precipitation not only forces the impacted water deeper into the aquifer, but also dilutes the impacted water at the water table. Maximum tritium results are presented on Figures 6.3 and 6.4 for the shallow and deep overburden, respectively, and in Table 6.2.

The data shows that the maximum extent of the tritium plumes are consistent with those shown on Figures 6.1 and 6.2.

Figure 6.5 presents the locations of two hydrogeologic cross-sections at the Site.

Hydrogeologic cross-sections A-A' and B-B' are presented on Figures 6.6 and 6.7, respectively. Figure 6.6 presents a cross-section along the groundwater flowpath from the Cooling Lake to northeast of the off-Site pond. Figure 6.7 presents a cross-section perpendicular to groundwater flow near the blowdown line. Both figures indicate that the greatest tritium values are at depth. However, the Wedron Formation clay till and the underlying shales act as aquitards, limiting the hydraulic communication between the groundwater in the overburden and the bedrock aquifer.

Using the most recent groundwater results, CRA calculated the mass of tritium in the overburden groundwater. The mass of tritium in the groundwater was determined at vacuum breakers VB-1 and at VB-2 and VB-3 (combined), with results of 0.19 Curies (Ci) and 2.05 Ci, respectively, or 2.24 Ci total on Site. The tritium mass was calculated by measuring the area the plume covers in the deep and shallow groundwater zones (Figures 6.1 and 6.2). The data are in Appendix K.

016841 (12) 31 CONESTOGA-ROVERS & ASSOCIATES

Periodic tritium analyses have been performed at selected locations at the Site to determine the variability in the data. In general, samples were collected weekly at each location. The locations involved in the periodic sampling program are presented on Figure 4.1, and the tritium results are presented in Table 6.3. Specifically, samples have been collected routinely at groundwater monitoring locations P-4, P-4D, P-13D, BL-9, BL-9D, S-2, S-2D, C-2, and C-2D, and at surface water sample locations SW-2 and Alpha Gate (on the perimeter ditch north of VB-1).

Appendix D shows tritium concentrations and groundwater elevations over time for the weekly sampling locations. The weekly tritium results indicate that tritium concentrations fluctuate over time, and the concentrations tend to vary with the groundwater elevation. In general, the tritium concentrations show a negative correlation with groundwater elevation in the locations south of Exelon pond (P-4, P-4D, P-13D, BL-9, and BL-9D on Figure D.1 of Appendix D), and a positive correlation with groundwater elevation in the locations north of Exelon Pond (S-2, S-2D, C-2, and C-2D on Figure D-2 of Appendix D). The negative correlation south of the pond is likely due to the fact that the increase in water level is from (non-tritiated) infiltrating water diluting the groundwater tritium. The tritium concentrations in the locations north of the pond are much closer to ambient atmospheric values in the area (200 pCi/L). This means that the precipitation infiltrating to the ground (raising the groundwater level) may have higher tritium concentrations than the groundwater and therefore tritium concentration increases with the increase in infiltrating water. The tritium concentrations in the surface water locations (SW-2 and Alpha Gate) fluctuate over time but do not appear to have a significant trend over time.

Groundwater samples from the private wells PW-10 and PW-11, which are completed in the deep bedrock north of the Site, indicate that tritium is at or below the background concentration in the deep bedrock aquifers. Samples from the private wells PW-7, PW-9, PW-14, and PW-15, which are completed in the channel sandstone deposits or the conglomerate, indicate that tritium is also below the background concentration in the channel sandstone deposits and the conglomerate. Maximum tritium results in all the private wells on site are presented in Figure 6.8 and in Table 6.4.

6.4 CONCEPTUAL MODEL OF TRITIUM RELEASE AND MIGRATION This section summarizes the current understanding of the mechanism for tritium releases to the groundwater at the Site and presents the conceptual model.

016841 (12) 32 CONESTOGA-ROVERS & ASSOCIATES

The historical data indicate that there were several releases of tritiated water from the vacuum breakers. In each case, water from the blowdown line was released to the surface and downward into the subsurface.

The surface releases from VB-2 and VB-3 flooded the low-lying area between the valves and Smiley road. The area that flooded is bounded by the mounded dirt covering the blowdown pipe on the east and south, Smiley Road to the north, and an estimated 300-400 feet to the west. The exact westerly boundary is not known but is estimated based on the topography of the area. This is generally the area where the most concentrated part of the groundwater plume is detected today. Releases from VB-1 flowed in groundwater toward the Site perimeter ditch.

The observations of Station personnel and the construction of the vacuum breaker valve vaults (valve pits) both suggest that water was not only released to the ground surface but also discharged vertically downward into the groundwater table. The vacuum breaker vaults are round concrete vaults or valve pits which extend down to the top of the blowdown line. There is no sealed bottom on these round concrete structures in order to allow access to the valve extending off the main blowdown pipe and to allow access to the pipe itself. The bottom of the vacuum breaker vaults is filled with gravel to allow the shallow water table to come into the vault under high water table conditions and to allow collected water to drain out the bottom. Therefore, when the valve failures occurred, most of the water released would have flowed downward within the vacuum breaker vault and recharged the water table through the bottom. Consequently, most of the blowdown line water was released to the subsurface as well as to the land surface in releases from the vacuum breakers.

The groundwater data collected also support the mechanism that a significant component of flow from releases was downward into the vacuum breaker vault (valve pit). Under this scenario, a portion of the tritium released from the vacuum breakers entered the groundwater near the vacuum breaker location and then traveled with groundwater at the estimated velocity of 80 ft/yr. to 170 ft/yr. In a sense, the vacuum breaker vaults would act as dry wells to allow the tritium to enter the groundwater (vertically) at a rate faster than normal subsurface infiltration.

There is evidence of this downward migration pathway in the detections of blowdown line indicators or fingerprints (sodium, chloride and tritium) at a few of the deeper temporary wells installed downgradient of VB-2 and VB-3, specifically, at BL-9D and BL-10D located near VB-2 and the deeper temporary wells located 300 to 500 feet downgradient (north-northwest) of VB-3. In the case of VB-3, the subsurface 016841 (12) 33 CONESTOGA-ROVERS & ASSOCIATES

mechanism occurred for a short time and allowed elevated levels of tritium to enter into the groundwater instantaneously, and then the discharge stopped.

The overland flow of water resulted in the source areas from each release extending much further downgradient than would be expected if the impacted water was only released directly to the groundwater at the blowdown line. This pattern of tritium appears to mimic what would have occurred for a continuous leak if the blowdown line was responsible for the tritium in the groundwater. Other evidence shows that continuous release is not the case, however. The tritium dating results are inconsistent with a slow continuous leak in the blowdown line (see Appendix H). Tritium dates in the deep overburden near the blowdown line are consistent with a leak that occurred in or around 2000. As described in the Poreda report, the shallow groundwater tritium date is consistent with diffusion of helium from deeper groundwater, but not with a recent release.

Exelon also collected groundwater samples adjacent to the blowdown line (near VB-2) to determine if the pipe was leaking. These groundwater samples were analyzed for tritium, sodium, and chloride. These results, which are presented in Table 6.5, indicate that the concentrations are similar to those in the background wells. This means that there is no continuous leak from the blowdown line near VB-2 and that the release was from the vacuum breaker failures.

The surface area of the plume and maximum distance from VB-2 and VB-3 (approximately 2,600 feet) gives the appearance that the releases occurred prior to 1998 if groundwater flow velocity is approximately 80 ft/yr. to 170 ft/yr. This is also somewhat misleading because the groundwater discharges to and mixes with Exelon Pond. In effect, the impacted water takes a "short cut" in the pond and, therefore, travels much further and faster than under normal groundwater flow conditions.

This rapid migration is supported by the groundwater contours that indicate a strong influence from the pond (Figures 5.6 and 5.7) and is also supported by the tritium dating data. These results for the water north of the pond indicate that the starting dates of the water were reset by equilibration with the atmosphere. This equilibration with the atmosphere could only have occurred in the pond, and therefore the tritiated water must be mixing with the surface water, releasing its 3He. This mixing not only has the effect of rapidly moving the impacted water further downgradient (to the north side of the pond), but also reducing the tritium concentration through dilution.

Despite the fact that the release at VB-1 occurred before those at VB-2 and VB-3, the plume at VB-1 is much smaller. This is because the release at VB-1 was smaller than the 016841 (12) 34 CONESTOGA-ROVERS & ASSOCIATES

other releases. It is also likely due to the fact that much of the shallow groundwater, which is migrating north from VB-1, is being intercepted by the perimeter ditch. A small portion of the tritiated groundwater discharges to the ditch and is carried off Site to the west. The deeper groundwater plume appears to be much smaller than expected based on its age and concentration, which may indicate that the ditch is also intercepting some of the deeper water.

The historical mining operations in the area (Appendix I) present the possibility that abandoned shafts or old exploration borings may act as conduits to the deeper water-bearing bedrock layers. However, the groundwater contours at the Site do not show any areas where this is occurring. Further, the chemistry from the private wells in the area do not contain concentrations of tritium that exceed background levels. In summary, based upon existing Site data the primary migration pathway of tritium has been laterally through the shallow sand aquifer from the north to the south and not downward into deeper hydrogeologic units.

016841 (12) 35 CONESTOGA-ROVERS & ASSOCIATES

7.0 ENDANGERMENT ASSESSMENT This Section of the report addresses the releases from the Recognized Environmental Conditions (the failed vacuum breakers) and any potential risks to human health and the environment. The intent of this section is to describe the potential risks from any completed exposure pathways.

In summary, based upon historical knowledge and data of the Braidwood Station operations and based upon chemical analyses in the blowdown line and in groundwater samples, the only Chemical of Concern is tritium. The discussions that follow are focused on the exposure pathways related to tritium.

7.1 HEALTH EFFECTS OF TRITIUM Tritium is a radioactive isotope of hydrogen. The most common forms of tritium are tritium gas and tritium oxide, which is also called tritiated water. The chemical properties of tritium are essentially those of ordinary hydrogen. Tritiated water behaves the same as ordinary water in both the environment and the body. Tritium can be taken into the body by drinking water, breathing air, eating food, or through skin absorption.

Once tritium enters the body, it disperses quickly and is uniformly distributed throughout the body. Tritium is excreted from the body through the urine, with a biological half-life of 10 days, the same as for water.

A person's exposure to tritium is primarily through the ingestion of water (drinking water) or through ingestion of waterbearing food products. Inhalation of tritium requires the water to be in a vapor form (i.e., through evaporation or vaporization due to heating). Inhalation is a minor exposure route when compared to direct ingestion or drinking of tritiated water. Absorption of tritium through the skin is possible, but tritium exposure is more limited here versus direct ingestion or drinking of tritiated water.

Tritium is weakly radioactive. It decays by emitting a low-energy beta particle that cannot penetrate deeply into tissue or travel far in air. It poses a potential health hazard only if it is taken into the body. The beta particle emitted by tritium when it decays is a form of ionizing radiation. For radiation protection purposes, all radiation exposure is considered to increase the risk of developing cancer, and the risk is considered to be proportional to dose, even at low levels for which there is no conclusive scientific evidence of radiation effects.

016841 (12) 36 CONESTOGA-ROVERS & ASSOCIATES

The EPA considers tritium to be one of the least dangerous radionuclides because it emits very weak radiation and leaves the body relatively quickly. Since tritium is almost always found in water, it goes directly into soft tissues and organs. The associated dose to these tissues is generally uniform and dependent on the tissues' water content.

Tritium does not concentrate in any one organ; therefore, the dose is spread through the entire body.

7.2 GROUNDWATER STANDARD The ingestion of tritium through drinking of potable water is a potential exposure route at this Site (refer to Section 8.4). Currently, the IEPA relies on a USEPA groundwater standard for tritium of 20,000 pCi/L (35 IAC 620 Section 410 (e)). The following is the basis of this standard per this section of the Act:

Beta Particle and Photon Radioactivity Except due to natural causes, the average concentration of beta particle and photon radioactivity from man-made radionuclides shall not exceed a dose equivalent to the total body organ greater than 4 mrem/year in Class I groundwater. If two or more radionuclides are present, the sum of their dose equivalent to the total body, or to any internal organ shall not exceed 4 mrem/year in Class I groundwater except due to natural causes.

Except for the radionuclides listed in subsection (e)(3), the concentration of man-made radionuclides causing 4 mrem total body or organ dose equivalent must be calculated on the basis of a 2 liter per day drinking water intake using the 168-hour data in accordance with the procedure set forth in NCRP Report Number 22, incorporated by reference at Section 620.125(a).

Except due to natural causes, the average annual concentration assumed to produce a total body or organ dose of 4 mrem/year of the following chemical constituents shall not be exceeded in Class I groundwater:

Critical Standard Constituent Organ (pCi/L)

Tritium Total Body 20,000 Strontium-90 Bone Marrow 8 016841 (12) 37 CONESTOGA-ROVERS & ASSOCIATES

Thus, the concentration of tritium in groundwater should not exceed the 20,000 pCi/L level at a potable water supply. Tritium concentrations that will protect human health are less than 20,000 pCi/L. CRA uses this standard for comparison purposes, comparing the analytical results presented in this report to the standard.

The surface water quality criteria for tritium (20,000 pCi/L) is based upon the same evaluation presented above as it addresses the ingestion and absorption exposure routes during recreational use of general resource surface water bodies. This standard is used herein for comparison purposes. Exelon will develop Site specific objectives under separate cover as discussed in Section 9.3.

7.3 SITE SPECIFIC BACKGROUND CONCENTRATIONS OF TRITIUM IN GROUNDWATER At the Braidwood Station, the background, or ambient, concentrations of tritium in the groundwater occur where there have been no releases. Specifically, background concentrations should occur in those areas of the shallow sand aquifer that are either upgradient of the vacuum breakers or downgradient but outside the plumes. Based on these criteria, the background concentration is 200 pCi/L. This conclusion is based upon a number of evaluations and assessments.

Dr. Robert Poreda, University of Rochester, who is an expert in the field of tritium dating, indicated that his testing in Nebraska and Wisconsin showed typical background values of 100 pCi/L. However, the background at Braidwood would likely be slightly higher given its location downwind of the Quad Cities, LaSalle, and Dresden Nuclear power plants. According to Dr. Poreda, the upper limit for rainfall he has measured is 200 pCi/L.

In addition, information on background concentrations of tritium in groundwater were obtained from a Michigan Department of Environmental Quality study. 7 According to this study, concentrations in Michigan groundwater today may be on the order of 160 to 320 pCi/L. Consequently, the assumption that background at the Site is 200 pCi/L is reasonable.

Finally, the laboratory that is currently performing the analysis of tritium in the groundwater samples collected at this Site has a lower limit of detection of 200 pCi/L.

This is a practical quantification limit above which the laboratory has confidence in their 7 Use of Tritium in Assessing Aquifer Vulnerability" available at http://www.deq.state.mi.us/documents/deq-dwrpd-gws-wpu-Tritium.pdf 016841 (12) 38 CONESTOGA-ROVERS & ASSOCIATES

quantitative estimate. Any result below this concentration is an estimate. The estimated values provided by the laboratory are still, nevertheless, at concentrations that are less than the 200 pCi/L background at this Site.

7.4 EXPOSURE ROUTE EVALUATIONS The potential exposure point pathways and potential receptors for tritium that was released from the three vacuum breakers (VB-1, VB-2, and VB-3) are discussed in the following sections. CRA has identified any incomplete and complete exposure pathways.

7.4.1 IDENTIFICATION OF POTENTIAL EXPOSURE PATHWAYS AND POTENTIAL RECEPTORS There are two mechanisms for tritium in the blowdown line water to reach the groundwater from the failed vacuum breakers:

• Direct discharge from the valve into the valve vault and downward into the groundwater table; and

• Overflow of the water from the top of the vault, through the manhole, and onto the land surface. Subsequently, the ponded water infiltrates downward to the water table.

7.4.1.1 DIRECT DISCHARGE SCENARIO The complete exposure routes or pathways for tritium migration to potential receptors for the first scenario, direct discharge to the groundwater, include:

1.1 Groundwater flow to the north (downgradient direction) to private water supply wells; 1.2 Groundwater flow to the north and subsequent discharge into the ponds north of Smiley Road; and 1.3 Groundwater flow to the north from VB-1 and into the perimeter ditch, which then flows north and west.

016841 (12) 39 CONESTOGA-ROVERS & ASSOCIATES

Under the first release scenario, direct discharge to the groundwater from the vacuum breaker, the potential receptors include off-property users of the shallow sand aquifer and recreational users of the northern off-Site ponds. In addition, there could be a potential worker exposure to tritium in the perimeter ditch, which is on Exelon's property.

7.4.1.2 OVERFLOW SCENARIO The complete exposure routes or pathways for tritium migration to potential receptors for the second scenario, overland surface flow, include:

2.1 Direct contact with standing or ponded water on the Braidwood Station Property at the time of the spill; 2.2 Seepage into the underlying vadose zone and into the groundwater; 2.3 Direct contact with surface water ponded at the time of the spill in the ditch south of Smiley Road; 2.4 Groundwater flow to the north (downgradient direction) to private water supply wells; 2.5 Groundwater flow to the north and into the ponds north of Smiley Road; and 2.6 Groundwater flow to the north from VB-1 and into the perimeter ditch, which then flows north and west.

Under the second release scenario, the potential receptors include Braidwood Station workers, contact with surface water ponded in the ditch on the south side of Smiley Road, off-property well users, and recreational users of off-property ponds. Also, there is the potential scenario where a worker could be exposed to tritium in the perimeter ditch. These potential receptors and the identified exposure routes are discussed in the following sections.

The water would be ponded or pooled on the surface before it seeped into the underlying soils. There is approximately 5 to 8 feet of unsaturated soils (vadose zone) above the water table. The ponded water would seep through these soils to the water table. As such, a small percentage of this water would initially remain in the soils above the water table after the spill. However, since tritium has characteristics of water it will not sorb onto the soil particles. Rather, it will remain as part of the residual water left in the soil pores. This residual tritium will eventually be flushed downward to the water 016841 (12) 40 CONESTOGA-ROVERS & ASSOCIATES

table. The infiltration of rain or snow melt will reduce the residual saturation by two methods: 8

• Flushing of pore water with tritium out of the soil column into the underlying water table; and

• Dilution of the residual tritium levels with recharge.

The likelihood of the unsaturated soils containing significant levels of tritium in pore water over any extended period is unlikely. The reduction of any residual tritium in the soil column should be rapid given the approximately 12 inches of precipitation recharge each year in Illinois (35 IAC 742). As such, the expected concentration of tritium in the soil column should be in the range of ambient concentrations for rain water (160 to 320 pCi/L) 9 and significantly below the groundwater standard (20,000 pCi/L).

Given the physical conditions with regard to residual tritium in the soil column; this exposure pathway is incomplete. Direct contact with tritium in soils beneath the former spill areas 10 is not a complete pathway because:

• This area is within the boundaries of the Braidwood Station property and, therefore, access is restricted to Exelon employees;

• This is not an active, operational area of the facility and as such subsurface excavations or other construction work is not performed that might expose workers to the subsurface soils; and

• Braidwood Station excavation protocols would require health and safety monitoring and preventative measures to eliminate exposure to soils that might have unsafe radiological conditions.

In summary, the soil exposure route to tritium in the Site area is incomplete.

Once in the groundwater, the tritium will migrate to the north with groundwater flow away from the vacuum breakers. There is no exposure route for the ingestion of groundwater on Exelon's property. The Station receives its potable water from the Kankakee River (approximately 5 miles east of the Site). In addition, Exelon's property is considered an industrial property, and existing zoning and other institutional controls 8 These mechanisms apply both to the water that ponded on the Braidwood Station property and to the water that ponded in the small ditch south of Smiley Road.

9 Use of Tritium in Assessing Aquifer Vulnerability, http://www.epa.state.il.us/water/tritium.html, Illinois Environmental Protection Agency, Bureau of Water, October 1997.

10 Including the small ditch south of Smiley Road.

016841 (12) 41 CONESTOGA-ROVERS & ASSOCIATES

would prevent the installation of potable water supply wells on the property. Therefore, there is no complete exposure route for groundwater ingestion on Exelon's property.

Groundwater containing tritium will migrate to the north (downgradient) of Exelon's property and onto adjacent private property. There are a number of private land owners to the north where the residential water supply is provided by private wells completed in the shallow sand aquifer. These shallow water supply wells are considered potential pathways. The land that is directly north of Smiley Road (where the Exelon Pond is located) is owned by the Braidwood Station. As such, the small area where there are exceedences of the groundwater standard does not have potable water wells in the shallow sand aquifer. However, migration of tritiated groundwater farther to the north of this is a potential exposure pathway.

Currently, there are no private water supply wells with tritium that exceed the groundwater standard. In addition, no private property contains groundwater with tritium at a concentration that exceeds the groundwater standard. These observations are based upon a wealth of groundwater data collected as part of this study.

To evaluate future conditions, CRA modeled the potential migration of the existing tritium located south of Smiley Road to the property to the north. BIOSCREEN, a USEPA analytical model, assessed the migration of tritium found within the main "plume" area south of Smiley Road. Appendix L presents the data used, the assumptions made, and the results of the analytical simulations. Figure 7.1 presents a graphical representation of the BIOSCREEN modeling for tritium. This figure depicts the shape of the extent of migration of the tritium from the area south of Smiley Road toward the north. Even with very conservative assumptions, the BIOSCREEN model predicts that tritium concentrations in groundwater under private property north of Smiley Road will not exceed the groundwater standard. Consequently, future exposure of private well users to tritium concentrations that exceed the groundwater standard is also incomplete. As a result of this modeling, Exelon concluded that no additional well owners require notification of potential impact to their wells.

The water well inventory, discussed in Section 4.3 and provided in Appendix G, indicates that there are a number of private and public (Village of Braidwood) water supply wells that are completed in the deep regional aquifer. These deep aquifers are found at depths of 100 to 1,600 feet bgs. Exelon has sampled 10 private water supply wells completed in the deeper aquifers and analyzed the groundwater as part of this investigation (see Figure 2.2 for the location of the deeper wells). For example, private wells PW-10 and PW-11 are downgradient of the main area of tritium-impacted groundwater. As can be seen in Appendix G and on Figure 6.8, these deeper wells did 016841 (12) 42 CONESTOGA-ROVERS & ASSOCIATES

not contain tritium that exceeded background. This is to be expected because the vertical movement of tritium into deeper formations is restricted by the following three regional aquitards (refer to Figure 5.1):

• The Wedron Formation of clayey till, which directly underlies the upper sand aquifer;

• The shales of the Carbondale Formation and the Spoon Formation; and

• The Scales Shale of the Maquoketa Group.

These three layers represent regional vertical barriers to groundwater flow. Moreover, the presence of these barriers eliminates the potential for tritium to migrate to the deep bedrock aquifers; therefore, the exposure pathway to deep bedrock water supply wells is incomplete.

It is possible that the former coal mining activities could have breached the shallower of the regional aquitards (Wedron Formation). Mining activities such as mine shafts, airshafts, and exploration holes would not have, however, breached the 70 to 80 feet thick Scales Shale Formation. This shale is found at a depth of over 200 feet bgs beneath the Site. Consequently, the Scales Shale would be a barrier to vertical groundwater flow to the regional aquifers. Again, the assertion that this pathway is functionally incomplete is supported by the results of sampling deeper bedrock wells. Tritium was not detected above background levels in any of these deeper wells.

Tritium has been found in surface water at the Site on three occasions. The first occasion was during the actual releases from the individual vacuum breakers when the water ponded on the land surface for a short time on the Braidwood Station property. 11 The second situation occurred when groundwater, containing tritium, discharged to the pond to the north of Smiley Road. The third situation occurred, in the case of the VB-1 area, when groundwater flowed into the perimeter ditch.

In the first situation, the potential for exposure no longer exists because the ponded water has seeped into the underlying soils and into the groundwater. The depth to the groundwater is at least 5 to 8 feet bgs at the Site. It is very unlikely that the water table will rise above the ground surface and create a surface water situation in the future.

Consequently, worker exposure (direct contact) on the Braidwood Station property to water ponded on the land surface is not possible. In addition, any further exposure beyond the initial ponding of water in the ditch to the south of Smiley Road is 11 And to some extent in the ditch located south of Smiley Road.

016841 (12) 43 CONESTOGA-ROVERS & ASSOCIATES

non-existent for the same reason. Any surface water in this ditch currently represents normal street run-off from the adjacent roadway and surrounding areas.

The second situation involves the transport of elevated levels of tritium in groundwater off the Braidwood Station property and into the pond to the north of Smiley Road. The pond is on private property, 12 has been used for recreational purposes in the past, and can be anticipated to be used for recreational purposes in the future. Therefore, there is a potential for direct contact and ingestion exposure to tritium by recreational users of this pond.

The third scenario involves the flow of tritium in groundwater from VB-1 into the perimeter ditch that flows to the north. The perimeter ditch is located within the boundaries and fence line of Exelon's property. As such, the only exposure would be worker exposure (direct contact) during maintenance or monitoring activities.

7.5

SUMMARY

OF EXPOSURE ROUTES In summary, there are three complete exposure routes for tritium:

• Groundwater ingestion by private well users when the wells are completed in the shallow sand aquifer;

• Recreational users of the ponds north of Smiley Road; and

• Braidwood Station workers involved with maintenance and monitoring of the perimeter ditch.

At this time, based upon the wealth of groundwater and surface water data provided in this report, none of the receptors at the above exposure points are at risk. The concentration of tritium in the groundwater or surface water at any of these three exposure points is significantly below the 20,000 pCi/L standard for groundwater.

Specifically, there is no private property in the Site area with a groundwater concentration of tritium that exceeds the groundwater standard (20,000 pCi/L) in the shallow sand aquifer 13 . The surface water samples collected from Exelon pond 14 and the 12 The pond directly north of Smiley Road (Exelon Pond) is on property recently purchased by Exelon and is now part of the Braidwood Station property. Exelon is constructing a fence to prevent use of the pond for recreational purposes, and the land will have its deed restricted to prevent the use of groundwater for potable purposes.

13 There is an area at the southeast corner of the pond directly north of Smiley Road that contains tritium that exceeds the groundwater standard. However, Exelon owns this land and restrictions are in place to prevent the installation and use of shallow wells on this property.

016841 (12) 44 CONESTOGA-ROVERS & ASSOCIATES

other nearby ponds to the northwest and northeast have not contained tritium that exceeds the 20,000 pCi/L groundwater criteria. Likewise, concentrations of tritium measured in surface water samples from the perimeter ditch as it flows off the Site have all been at levels less than the 20,000 pCi/L groundwater criteria. In summary, although there are three potentially complete exposure routes for tritium migration from the RECs (historic vacuum breaker releases), there has not been an exposure to those receptors.

Further, predictive calculations indicate that there will not be an exposure to these receptors in the future.

14 This pond is currently owned and controlled by Braidwood Station.

016841 (12) 45 CONESTOGA-ROVERS & ASSOCIATES

8.0 CONCLUSION

S The purpose of this report is to provide the IEPA a summary of Site characteristics as they relate to the sources, migration pathways, and extent of tritium in groundwater at the Braidwood Station Site.

Based on all of the studies completed to date, CRA concludes:

• Groundwater use in the Site area is both in the upper shallow sand aquifer (20 to 30 feet deep) and in the deeper bedrock formations used regionally for municipal and private water supplies (depths of 600 to 1,700 feet).

• The upper, shallow groundwater flows beneath the Site in a generally south to north manner, flowing from the Cooling Lake toward the ponds located north of the Braidwood Station property.

• Depth to water in this upper shallow sand aquifer ranges from 5 to 15 feet. The deeper bedrock water supply aquifers are separated from the shallow system by a number of regionally identified aquitards.

• Braidwood Station employs the blowdown line to return water from the Cooling Lake back to the Kankakee River. This blowdown line also serves as a permitted discharge point for the Station's sewage treatment plant and liquid radwaste system.

• The discharges from liquid radwaste contain tritium.

• Historical failures at the three vacuum breaker valves (VB-1, VB-2, and VB-3) have resulted in the release of tritium to the groundwater at this Site. The distributions of tritium in groundwater at this Site are consistent with historical releases from these three subject vacuum breakers.

• There are two localized areas on the Site where tritium is detected above the groundwater standard (20,000 pCi/L). The first area is south of Smiley Road and downgradient of VB-2 and VB-3 is approximately 4.5 acres. The second area is north of VB-1 and is less than 2.0 acres.

• Tritium above the background or ambient concentration (assumed to be 200 pCi/L in this study) has migrated into, and through, the pond located north of Smiley Road. The distance to the leading edge of the tritium plume (above the ambient concentration) from the source (VB-2 and VB-3) is approximately 2,400 to 2,800 feet.

• Deeper private water supply wells that are downgradient of the main tritium plume contain ambient concentrations of tritium. Regional aquitards act as vertical barriers to migration of tritium from surficial aquifers to deeper bedrock aquifers. This finding is consistent with an understanding of vertical groundwater flow.

016841 (12) 46 CONESTOGA-ROVERS & ASSOCIATES

• There are three complete exposure routes, or pathways, for tritium migration at the Site involving the following receptors:

• Groundwater ingestion by private well users

• Recreational users of the ponds

• Braidwood Station workers

• At this time, based upon the wealth of groundwater and surface water data provided in this report, none of the above receptors are at risk.

• A BIOSCREEN model (a future migration analysis) indicates that even under conservative assumptions, the elevated concentrations of tritium will not migrate to private property at levels that exceed the groundwater standard.

In summary, CRA believes that the information collected to date is sufficient to develop future documents to support remediation of the Site. The nature of the sources, the extent of the contamination, the fate and transport of the contamination, the identification of complete exposure routes and receptors, and the future potential for migration have been well characterized.

The studies performed to date are sufficient to begin remedial action planning and develop remedial objectives. There are, however, some minor data gaps that need to be filled as part of the remedial action planning process. These requirements are clearly stated in the next section.

016841 (12) 47 CONESTOGA-ROVERS & ASSOCIATES

9.0 PLAN OF ACTION The following discussion presents a plan of proposed activities intended to be completed in the near future.

9.1 FILL DATA GAPS There are no significant data gaps with regard to characterization. However, there are some items that need to be addressed to better define potential remedial actions. For instance, additional water level and tritium data collection within and around the perimeter ditch would be useful for developing controls to prevent further tritium migration. Also, additional water level monitoring near the pond north of Smiley Road will be helpful in understating the hydraulics of the pond and its use in a remedial action. The pond north of Smiley Road has been instrumented with a pressure transducer to continuously monitor the water levels.

9.2 GROUNDWATER MONITORING Exelon will prepare a plan to install new monitoring wells and abandon temporary wells. In addition, this plan will outline the frequency of monitoring and analyses for the permanent monitoring well network. Trigger levels of tritium concentrations will be developed and discussed in this plan. Eventually, this plan will be integrated with the remedial action selected for the Site and its operation and monitoring requirements.

Exelon will install permanent 2-inch diameter monitoring wells to be part of the long term, routine, groundwater monitoring program. Some temporary wells will be plugged and abandoned.

9.3 REMEDIATION The tritium concentrations in groundwater and surface water at the Site were compared to the 20,000 pCi/L standard provided in 35 IAC 620 Section 4.10 (e). This standard is for a Class I groundwater as characterized by 35 IAC 620 Section 210. The groundwater in the shallow sand aquifer is considered a Class I aquifer based upon its hydraulic properties and its use as a potable water supply in the Site area.

016841 (12) 48 CONESTOGA-ROVERS & ASSOCIATES

Exelon will prepare a Remedial Objectives Report (using the guidance provided 35 IAC 740), which will be used to develop a Remedial Action Plan (RAP) for this Site.

CRA anticipates that procedures presented in the Tiered Approach to Corrective Action Objectives (TACO) (35 IAC 742) will be use to develop these Remedial Objectives.

Data gathering activities to be undertaken include:

• Pumping and water level monitoring at the existing Recovery Wells to better assess the hydraulic properties for the shallow sand aquifer;

• Depth-specific sampling in the pond located north of Smiley Road to better estimate tritium concentrations if the pond is to be pumped; and

• Sampling of groundwater for general chemistry and other parameters which might be required for design purposes or for regulatory requirements.

Exelon has already initiated a feasibility study of various potential remedial actions.

One option that can be implemented quickly easily is pumping the surface water from Exelon Pond, piping the water to the south, and discharging the water (untreated) into the blowdown line at VB-2. A similar approach is being considered for the smaller tritium plume near the perimeter ditch and north of VB-1. Here, the surface water in the perimeter ditch or a recovery well would also be pumped and piped directly to the blowdown line at VB-1. 15 This remedial action is meant to be an interim or time critical remedy that will then become part of a long term remedial action plan. In other words, this remedy can be implemented soon, but other remedial components such as additional groundwater pumping, discharge to the new blowdown line, or monitored natural attenuation will take longer.

These interim remedies (either the pond-to-blowdown line or pumping the plume near the perimeter ditch-to-blowdown line) have been selected because they will achieve these goals:

• Design and construction that can be completed quickly;

• Regulatory review is currently proceeding;

• These remedies prevent further migration of the groundwater with tritium above the 20,000 pCi/L standard past the pond or into the perimeter ditch; 15 At this time Exelon is considering either upgrading the existing blowdown line and its vacuum breaker valves or perhaps installing a new blowdown line.

016841 (12) 49 CONESTOGA-ROVERS & ASSOCIATES

• A system which prevents the further off-Site migration of residual tritium greater than 200 pCi/L;

• This system will slow, if not stop, the migration of tritium above the background standards to private property north of the Exelon Pond; and

• This system will reduce the mass of tritium in the groundwater.

At the time of this report Exelon has been in discussion with the IEPA, the Office of the Attorney General, and the Will County State's Attorney regarding this interim remedial action.

016841 (12) 50 CONESTOGA-ROVERS & ASSOCIATES

10.0 REFERENCES

CITED Bouwer, H. and R.C. Rice, 1976. A slug test method for determining hydraulic conductivity of unconfined aquifers with completely or partially penetrating wells, Water Resources Research, vol. 12, no. 3, pp. 423-428.

Illinois Administrative Code Title 35 Part 742, Tiered Approach to Corrective Action Objectives, Illinois Pollution Control Board, effective February 5, 2002.

Sargent and Lundy, 1988. Updated Final Safety Analysis Report (UFSAR), December.

Schicht, Richard J., J. Rodger Adams, and John B. Stall, 1976. Water Resources Availability, Quality, and Cost in Northeastern Illinois, Illinois State Water Survey Report of Investigation 83.

Visocky, Adrian P., Marvin G. Sherrill, and Keros Cartwright, 1985. Geology, Hydrogeology, and Water Quality of the Cambrian and Ordovician Systems in Northern Illinois, Illinois State Geological Survey, Illinois State Water Survey, Cooperative Groundwater Report 10.

Visocky, Adrian P., 1997. Water-Level Trends and Pumpage in the Deep Bedrock Aquifers in the Chicago Region, 1991-1995, Illinois State Water Survey Circular 182.

016841 (12) 51 CONESTOGA-ROVERS & ASSOCIATES

CHANNAHON R

RIVE IS NO I LLI 0 4000 8000ft MORRIS LEGEND VB-1 VACUUM BREAKER LOCATION AND IDENTIFIER BLOW DOWN LINE WILMINGTON COAL CITY KAK 9

12 3 KAN TE 5 U TE O

R OU R EE R IVER BRAIDWOOD VB5 VB6 VB8 VB9 VB10 VB11 VB4 VB3 VB7 EXELON NUCLEAR STATION VB1 VB2 AREA OF INVESTIGATION GODLEY COOLING LAKE BRACEVILLE figure 1.1 SITE LOCATION MAP EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA010 MAR 21/2006

0 200 600ft POND EXELON POND POND VB-3 EXELON NUCLEAR STATION VB-2 VB-1 LEGEND EXISTING FENCE LINE BLOWDOWN LINE figure 2.1 PLANT PROPERTY LINE VB-3 VACUUM BREAKER LOCATION GENERAL SITE BOUNDARIES AND FEATURES EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA011 MAR 21/2006

SOURCE: EXELON NUCLEAR OUTDOOR PIPING ARRANGEMENT, M-900 SHEET NUMBER 6 & 3.

NOT TO SCALE figure 3.1 SCHEMATICS OF THE BLOWDOWN LINE AND VACUUM BREAKERS EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA021 MAR 21/2006

G-2 G-3 G-1 G-2D PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 S-2 S-2D S-3 S-1 PW-8 S-1D F-8D S-7 C-1D S-7D C-1 F-3D S-5 S-6 S-4 PW-7 S-4D C-2D C-2 POND F-7D P-14 MW-110 P-12 P-2D P-3 P-14D F-5D P-2 F-6D P-11 PW-6 PW-15 F-4D BL-19 PW-5 PW-14 P-1 F-2D PW-4 P-10 F-1 EXELON POND F-1D POND BL-18 P-9 P-7 P-13D P-4D BL-17D PW-2 P-8 P-6 P-5D P-4 P-5 BL-17 VB-3-6 RW-1 MW-112 VB2-9D VB-2-6 RW-4 RW-3 RW-2 VB-3-5 MW-111 MW-112D VB-3-9D VB-3-4 BL-16D VB-3-7D MW-111D VB-2-6D VB-2-5 VB-2-3 MW-113D VB-3-4D VB-3-7 MW-109 PW-1 PW-3 VB2-9 VB-2-5D MW-113 BL-16 VB-2-4 VB-3-3 VB-3-8 VB-2-8 VB-2-7 MW-103 VB-3-1 VB-3-10D BL-15D VB-3-2 BL-15 VB1-6D VB-2-7D VB-3-10 VB-2-2D MW-105D VB-3 VB-1-6 MW-104 VB-2-2 BL-12D MW-105 BL-14D VB-1-9 VB1-9D VB-2-1 BL-14 BL-12 BL-13 BL-13D VB-1-7 VB-1-7D BL-20D VB-1-8 MW-102 BL-11D VB-1-8D VB-2 BL-11 BL-10 VB-1-3 BL-09 EXELON NUCLEAR STATION VB-1-5 VB1-3D VB1-5D D-3 D-4 BL-10D BL-08 BL-09D VB-1-4 VB1-4D D-2 D-3D D-2D BL-07 MW-101 VB1-2D D-5 VB-1-2 BL-06 MW-107 D-1D BL-05 VB-1-1 BL-01 D-1 BL-04 MW-106 VB-1 VB-1-1D BL-02 BL-03 MW-108 MW-106D LEGEND EXISTING FENCE LINE MW-105 SHALLOW MONITORING WELL LOCATION BLOWDOWN LINE MW-113D DEEP MONITORING WELL LOCATION PLANT PROPERTY LINE PW-5 PRIVATE WELL LOCATION figure 4.1 BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION P-11 SHALLOW TEMPORARY WELL LOCATION BL-17D DEEP BLOWDOWN LINE SAMPLING LOCATION P-4D DEEP TEMPORARY WELL LOCATION GROUNDWATER MONITORING LOCATIONS VB-3 VACUUM BREAKER LOCATION RW-3 SHALLOW RECOVERY WELL LOCATION EXELON GENERATION BRAIDWOOD STATION VB-3-7 VACUUM BREAKER SAMPLING LOCATION RW-2 DEEP RECOVERY WELL LOCATION 16841-11(012)GN-WA013 MAR 21/2006

0 200 600ft SW-3 POND SW-4 SG-C DS-3 ALPHA GATE EXELON POND SG-A POND PW-6P SW-2 SG-B SW-1 SG-1 DS-2 DS-6 EXELON NUCLEAR STATION SG-2 DS-1b DS-1 DS-10 DS-1a DS-9 SG-3 DS-11 DS-8 LEGEND EXISTING FENCE LINE BLOWDOWN LINE PLANT PROPERTY LINE figure 4.2 SG-1 DS-6 STAFF GAUGE LOCATION DITCH SAMPLING LOCATION SURFACE WATER MONITORING LOCATIONS SW-2 SURFACE WATER SAMPLING LOCATION EXELON GENERATION BRAIDWOOD STATION PW-6P POND SAMPLING LOCATION 16841-11(012)GN-WA014 MAR 21/2006

SOUTHWEST NORTHEAST 600 600 S&G OVERBURDEN EQUALITY FORMATION AQUIFER 580 580 WEDRON FORMATION 560 560 CARBONDALE FORMATION PENNSYLVANIA AQUITARD 540 540 COAL SHALES 520 520 SPOON FORMATION 500 500 SHALLOW BEDROCK AQUIFER 480 480 SILURIAN DOLOSTONES 460 460 ELEVATION IN FEET (MSL)

UNDIFFERENTIAL SILURIAN DOLOSTONES 440 (NOT PRESENT AT THE SITE) 440 420 420 400 400 380 380 360 360 ORDOVICIAN SHALES 340 340 320 MAQUOKETA SHALE GROUP AQUITARD 320 300 300 280 280 260 260 250 250 ORDOVICIAN SANDSTONES DEEP BEDROCK AQUIFER LIMESTONE/DOLOSTONES GALENA AND PLATTEVILLE GROUPS (DEEP BEDROCK AQUIFER) FROM 250 TO 0 GLENWOOD - ST. PETER FORMATION (DEEP BEDROCK AQUIFER) FROM 0 TO -280 CAMBRIAN IRONTON FORMATION (DEEP BEDROCK AQUIFER) FROM -280 TO -1050 SANDSTONES EAU CLAIRE SCALE: HORIZONTAL 1"=400' VERTICAL 1"=40' figure 5.1 LEGEND WATER BEARING UNIT REGIONAL STRATIGRAPHIC SECTION AQUITARD LAYER EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA015 MAR 21/2006

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 PW-8 PW-7 POND PW-6 PW-15 PW-5 PW-14 PW-4 EXELON POND POND PW-2 PW-1 PW-3 VB-3 EXELON NUCLEAR STATION VB-2 VB-1 LEGEND EXISTING FENCE LINE BLOWDOWN LINE PLANT PROPERTY LINE figure 2.2 VB-3 VACUUM BREAKER LOCATION PRIVATE WELL LOCATION PRIVATE WATER SUPPLY WELL LOCATIONS PW-5 PRIVATE WELL LOCATION SCREENED IN SHALLOW AQUIFER EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA012 MAR 21/2006

0 20000 50000ft 750 700 0 0 55 50 65 60 0 0 45 0

WINNEBAGO BOONE MC HENRY LAKE 400 0

75 0

40 700 0

35 0 0 75 30 25 0

OGLE DEKALB KANE COOK 20 0

15 0

-50 0 DUPAGE 100

-50 750 50 LEE 0 100

-50 50 KENDALL WILL 70 0

50 0 15 0

LASALLE

-50 65 0

600 550 GRUNDY 500 450 200 KANKAKEE 250 300 450 350 40 0

LEGEND 45 COUNTY BOUNDARY 0

450 BEDROCK GROUNDWATER LEVEL CONTOUR (1975)

SOURCE: UFSAR FIGURE 2.4-40 DATED OCTOBER 1975.

figure 5.2 REGIONAL DEEP BEDROCK GROUNDWATER LEVEL CONTOURS EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA016 MAR 21/2006

SOUTHWEST NORTHEAST 620 620 LAKE SCREEN HOUSE EXISTING GROUND SURFACE 600 600 OVERBURDEN BLOWDOWN LINE EQUALITY FORMATION 580 580 AQUIFER WEDRON FORMATION 560 560 CHANNEL SANDSTONE DEPOSITS CARBONDALE 540 FRANCIS CREEK SHALE 540 520 SILTSTONE CONG LOME 520 PENNSYLVANIA SHALES RATE SHALE 500 COAL 500 480 480 SPOON FORMATION 460 460 ELEVATION IN FEET (MSL)

AQUITARD 440 440 420 420 400 400 ORDOVICIAN SHALES 380 380 MAQUOKETA SHALE GROUP 360 360 340 340 320 320 300 300 GALENA AND PLATTEVILLE GROUPS (DEEP BEDROCK AQUIFER) FROM 250 TO 0 ORDOVICIAN GLENWOOD - ST. PETER FORMATION (DEEP BEDROCK AQUIFER) FROM 0 TO -280 DEEP 280 280 BEDROCK CAMBRIAN AQUIFER SCALE: HORIZONTAL 1"=400' VERTICAL 1"=40' LEGEND WATER BEARING UNIT AQUITARD LAYER figure 5.3 SITE SPECIFIC GEOLOGIC CROSS-SECTION (UFSAR)

EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA017 MAR 21/2006

G-2D (566.05)

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 S-2D S-1D (569.22)

(567.94) PW-8 C-1D PW-7 (571.00)

POND S-4D (569.41)

P-2D (572.38)

PW-6 PW-15 PW-5 PW-14 PW-4 EXELON POND F-1D (571.27) POND P-5D P-13D P-4D (569.34) BL-17D (569.11) (569.46) (573.01)

VB-2-6D RW-3 RW-2 RW-1 PW-2 (572.01) (572.24) (572.59) (571.68) VB-3-4D (571.18)

PW-3 RW-4 VB-2-5D MW-113D VB-3-9D VB-3-7D PW-1 VB-2-9D (572.31) (571.76) (571.18) BL-16D (572.24)

(572.14)

(570.26) (573.28)

BL-15D MW-105D VB-1-6D VB-2-7D (573.54) (573.22)

(574.86) VB-3-10D VB-3 (575.51)

VB-2-2D (572.99)

(566.99) BL-14D BL-12D BL-13D (570.96)

(570.10) (573.55)

EXELON NUCLEAR STATION BL-9D (570.65)

VB-2 D-3D (571.91)

D-2D D-1D (571.65)

(572.82) MW-106D VB-1 (572.70)

LEGEND EXISTING FENCE LINE PW-5 PRIVATE WELL LOCATION BLOWDOWN LINE P-4D TEMPORARY WELL LOCATION PLANT PROPERTY LINE RW-2 RECOVERY WELL LOCATION figure 5.4 BL-17D BLOWDOWN LINE SAMPLING LOCATION (590.59) ESTIMATED CLAY ELEVATION (ft AMSL)

VB-3 VACUUM BREAKER LOCATION BOTTOM OF SAND/TOP OF CLAY CONTOUR ESTIMATED BOTTOM OF SAND/TOP OF CLAY MAP CONTOURS VB-3-7D VACUUM BREAKER SAMPLING LOCATION EXELON GENERATION BRAIDWOOD STATION MW-113D MONITORING WELL LOCATION 16841-11(012)GN-WA020 MAR 21/2006

P-9 BL-17D BL-17 0 100 200ft P-8 (0.01)

P-6 P-5 P-5D P-4 P-4D P-13D P-7 PW-2 VB-2-6 RW-1 VB-3-5 VB-2-9D RW-2 VB-3-9D VB-3-6 VB-2-3 RW-3 VB-2-6D RW-4 VB-2-5 VB-3-4 BL-16D PW-3 VB2-9 VB-2-5D MW-113D VB-3-4D BL-16 VB-3-7D MW-113 (0.00) VB-3-7 PW-1 (0.00)

VB-3-3 VB-2-4 VB-3-8 MW-103 VB-2-7 VB-3-1 VB-3-10D BL-15D VB-2-7D BL-15 (0.03)

VB-2-8 VB-3-10 VB-3-2 MW-105D VB-3 MW-104 VB-2-2D MW-105 VB-2-2 (-0.37) BL-14D BL-14 BL-12D (-0.29)

VB-2-1 BL-12 BL-13D

(-0.01) BL-13 (0.01)

BL-20D MW-102 BL-11D BL-11 BL-10 (0.02)

BL-10D VB-2 (0.00)

BL-09 BL-09D BL-08 (-0.01)

BL-07 BL-06 MW-101 MW-106 MW-106D LEGEND MW-105 SHALLOW MONITORING WELL LOCATION EXISTING FENCE LINE MW-113D DEEP MONITORING WELL LOCATION BLOWDOWN LINE PW-5 PRIVATE WELL LOCATION PLANT PROPERTY LINE P-11 SHALLOW TEMPORARY WELL LOCATION figure 5.5 BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION P-4D DEEP TEMPORARY WELL LOCATION BL-09D DEEP BLOWDOWN LINE SAMPLING LOCATION RW-3 SHALLOW RECOVERY WELL LOCATION VERTICAL GROUNDWATER GRADIENTS ALONG BLOWDOWN LINE VB-3 VACUUM BREAKER LOCATION RW-2 DEEP RECOVERY WELL LOCATION EXELON GENERATION BRAIDWOOD STATION VB-3-7 VACUUM BREAKER SAMPLING LOCATION (0.01) POSITIVE VERTICAL GRADIENT = UPWARD

(-0.01) NEGATIVE OR ZERO VERTICAL GRADIENT = DOWNWARD 16841-11(012)GN-WA028 MAR 21/2006

G-1 G-2 G-3 (586.02) (586.08)

PW-11 0 200 600ft PW-13 PW-12 PW-10 S-2 PW-9 (588.62)

S-3 S-1 PW-8 (588.59)

(588.54)

S-7 (589.75) PW-7 C-1 POND S-6 S-4 S-5 (589.00)

(589.26) (589.38)

(589.59)

C-2 MW-110 P-2 P-14 (587.81) SG-C P-12 (590.46) P-3 (589.64) V (590.35)

P-11 PW-6 PW-15 (590.03) PW-5 P-1 BL-19 PW-14 (590.57) (590.62)

PW-4 P-10 (590.35)

F-1 EXELON POND SG-A (589.06) POND BL-18 (591.07)

P-9 SG-B (590.75) BL-17 P-7 P-5 P-4 (590.61) (590.93) (591.25)

(590.72)

P-8 P-6 MW-113 (590.65) VB-3-5 PW-2 RW-4 RW-3 (590.80) VB-3-6 RW-1 MW-112 (591.30) VB-3-7 MW-111 (590.90)

(590.85) PW-1 PW-3 VB-2-6 VB-2-5 VB-2-3 VB-3-3 VB-3-4 (591.58)

MW-109 (590.65) VB-2-9 (590.52) (590.94) BL-16 (591.24) (591.04)

(590.82) (590.99)VB-2-4 (591.25) VB-3-8 VB-2-8 (590.87) MW-103 VB-3-1 BL-15 (591.69)

(591.09) (591.24)

VB-2-7 (591.41)

VB-1-9 VB-1-6 VB-3-10 VB-3-2 VB-3 (591.23) VB-2-2 (591.40) (591.53)

(591.49) MW-104 MW-105 (591.56)

VB-2-1 (594.69)

(590.21)

VB-1-7 (591.14) BL-11 BL-13 BL-14 (591.47) (591.24) BL-12 (591.43) (591.61)

VB-1-8 MW-102 VB-1-5 (591.61) (591.92) (591.55)

EXELON NUCLEAR STATION VB-1-3 (591.64) D-4 BL-08 BL-09 BL-10 VB-2 (591.89) D-3 (591.46) (591.16) (591.48) (591.34)

VB-1-2 (591.63) D-2 (591.61) BL-07 MW-107 (592.26) VB-1-4 D-5 MW-101 (592.82) (591.19) D-1 (591.70) BL-05 BL-06 BL-01 (591.42)

(591.79) (591.21) (591.20)

(592.49) MW-108 BL-04 VB-1 VB-1-1 BL-02 BL-03 (592.63) (592.25) (591.59) (591.41)

MW-106 (596.25)

LEGEND EXISTING FENCE LINE MW-105 MONITORING WELL LOCATION BLOWDOWN LINE PW-5 PRIVATE WELL LOCATION PLANT PROPERTY LINE P-11 TEMPORARY WELL LOCATION figure 5.6 VB-3 VACUUM BREAKER LOCATION RW-3 RECOVERY WELL LOCATION BL-19 BLOWDOWN LINE SAMPLING LOCATION (590.80) GROUNDWATER ELEVATION (ft AMSL) GROUNDWATER LEVEL CONTOURS - JANUARY 2006 VB-3-7 SG-B VACUUM BREAKER SAMPLING LOCATION STAFF GAUGE LOCATION GROUNDWATER ELEVATION CONTOUR (ft AMSL)

GROUNDWATER FLOW DIRECTION SHALLOW GROUNDWATER ZONE NOTE:

EXELON GENERATION BRAIDWOOD STATION MONITORING WELL DATA TAKEN JANUARY 3, 2006 TO JANUARY 5, 2006.

16841-11(012)GN-WA018 MAR 21/2006

G-2D (587.00)

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 S-2D S-1D (588.62)

F-8D (589.05) PW-8 (588.72)

S-7D C-1D (589.73) (589.08)

F-3D POND (588.69) S-4D PW-7 F-7D C-2D (587.89)

F-6D P-14D F-5D P-2D (590.61)

(588.02) (590.47)

(589.31)

SG-C F-4D PW-6 PW-15 PW-5 PW-14 (588.72)

PW-4 F-2D (590.00)

F-1D EXELON POND SG-A (589.09) POND SG-B P-5D BL-17D P-13D P-4D (590.46) (590.60) (590.74) (591.31)

VB-2-9D PW-2 (590.24) RW-4 RW-3 RW-2 RW-1 VB-3-4D MW-112D (591.25)

PW-3 VB-2-6D VB-2-5D MW-113D VB-3-9D BL-16D VB-3-7D MW-111D (590.96) PW-1 (590.98) (591.59)

(590.66) (590.17) (590.77) (591.25)

(590.70)

BL-15D VB-3-10D (591.58)

VB-1-6D VB-2-7D (591.37) MW-105D VB-1-9D (591.02) VB-2-2D (591.72) VB-3 (590.70) BL-12D (591.12) (591.47) BL-14D BL-20D VB-1-8D BL-13D (589.20)

VB-1-7D BL-10D (591.29)

(591.97) (591.35) (591.65)

VB-1-5D (591.60) BL-09D BL-11D EXELON NUCLEAR STATION VB-1-3D (592.00) (591.28) VB-2 (591.53)

(592.30) D-3D VB-1-4D (591.62)

(593.11)

VB-1-2D D-2D (592.49) D-1D (591.71)

(591.77)

VB-1 VB-1-1D MW-106D (592.29)

LEGEND EXISTING FENCE LINE PW-5 PRIVATE WELL LOCATION BLOWDOWN LINE P-4D TEMPORARY WELL LOCATION PLANT PROPERTY LINE RW-2 RECOVERY WELL LOCATION BL-17D BLOWDOWN LINE SAMPLING LOCATION (590.59) GROUNDWATER ELEVATION (ft AMSL) figure 5.7 VB-3 VACUUM BREAKER LOCATION GROUNDWATER ELEVATION CONTOUR (ft AMSL)

VB-3-7D VACUUM BREAKER SAMPLING LOCATION GROUNDWATER FLOW DIRECTION GROUNDWATER LEVEL CONTOURS - JANUARY 2006 MW-113D SG-B MONITORING WELL LOCATION STAFF GAUGE LOCATION DEEP GROUNDWATER ZONE NOTE:

EXELON GENERATION BRAIDWOOD STATION MONITORING WELL DATA TAKEN JANUARY 3, 2006 TO JANUARY 24, 2006.

16841-11(012)GN-WA019 MAR 21/2006

0 200 600ft G-1 G-2 G-3 (133) (87) (81)

PW-11 PW-13 SW-3 (96) PW-12 PW-10 PW-9 A-1 S-2 (33) S-1 (62) S-3 (83) (57)

PW-8 POND C-1

(-80)

S-5 S-4 PW-7 S-6 (1874) (1086)

(411)

C-2 SW-4

(-48)

(83)

MW-110 P-12 P-2 P-3

(-104) (1622) (2045) (2537)

DS-3 P-11 PW-15 (1476) PW-6 BL-19 PW-5 PW-14 (37)

PW-4 P-10 PSG-1 EXELON POND P-1 (1723)

(2484)

F-1 POND PW-6P

(-44)

(142) 0 20 BL-18 (108)

P-9 SW-2 (111) SW-1 (2441)

(2464) P-5 P-4 PSG-2 (6166) BL-17 P-8 (9588)

(2212) P-7 P-6 (-44)

(1210) RW-4 (110) MW-113 VB-3-6 RW-1 VB-3-5 MW-112 PW-2 (53572)

RW-3 (4008) (95)

SG-1 MW-111 (-127) VB-3-3 VB-3-7 PW-3 VB-2-6 VB-2-5 VB-2-3 RW-2 (43894)VB-3-4 200 MW-109

(-78)

(1412) (3834) (3940) (29286) BL-16

(-126)

PW-1 5 00 VB-3-2 (3364) VB-3-8 (305) (32830) BL-15 (171)

VB-2-8

(-103) VB-2-7 VB-2-4 MW-103 0 VB-3-10 (146)

(3664) (2497) VB-3-1 (12076)

VB-1-6 VB-3 VB-1-9 (95)

(-60) MW-104 5000 (5959) MW-105 BL-14 (142) (169)

(107) VB-2-2 VB-2-1 (-37)

VB-1-7 (5232) BL-13 (140) (2) MW-102 VB-1-8 BL-12 (-16)

DS-2 BL-09 (58) BL-11 (-39)

VB-1-3 (57) DS-6 20 (4809)

(206) VB-1-5 BL-08 0 VB-2 (13)

(130) D-4 BL-10 20 VB-1-4 BL-07 (-104)

(91) (90) 0 (384) D-3 BL-06 (39)

MW-107 (-168) D-5 MW-101 VB-1-2 D-2 (114)

(269) BL-05 (162)

(337) BL-02 D-1 (-165) (73)

VB-1 (-13) BL-03 BL-04 (102)

(156) SG-2 BL-01 (0) (40) MW-106 VB-1-1 (425) (70) MW-108 DS-1 DS-10 (-35)

(91) DS-1b DS-1a DS-9 DS-11 SG-3 DS-8 DS-7 LEGEND:

EXISTING FENCE LINE EXISTING PERIMETER DITCH LIMITS TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIES/LITER)

BLOWDOWN LINE TRITIUM RESULTS 100,000 TO 200,000 PLANT PROPERTY LINE TRITIUM RESULTS 60,000 TO 100,000 BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION TRITIUM RESULTS 40,000 TO 60,000 VB-3 VACUUM BREAKER LOCATION TRITIUM RESULTS 20,000 TO 40,000 VB-3-7 VACUUM BREAKER SAMPLING LOCATION TRITIUM RESULTS 10,000 TO 20,000 MW-105 SHALLOW MONITORING WELL LOCATION TRITIUM RESULTS 5,000 TO 10,000 PW-5 PRIVATE WELL LOCATION TRITIUM RESULTS 200 TO 5,000 P-11 SHALLOW TEMPORARY WELL LOCATION TRITIUM RESULTS 0 TO 200 PSG-1 STAFF GAUGE LOCATION NOTE:

BACKGROUND TRITIUM CONCENTRATION: 200 pCi/L DS-6 DITCH SAMPLING LOCATION DRINKING WATER STANDARD FOR TRITIUM: 20,000 pCi/L SW-2 TRITIUM DATA FOR SAMPLES COLLECTED THROUGH SURFACE WATER SAMPLING LOCATION JANUARY 30, 2006. CONTOURS WERE GENERATED RW-3 SHALLOW RECOVERY WELL LOCATION USING LOG VALUES. figure 6.1 PW-6P POND SAMPLING LOCATION ESTIMATED TRITIUM RESULTS (2,484) TRITIUM RESULT IN GROUNDWATER SHALLOW GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION 200 TRITIUM CONTOUR 16841-11(012)GN-WA022 MAR 21/2006

0 200 600ft G-2D (67)

PW-11 PW-13 PW-12 PW-10 S-2D A-1D PW-9

(-2)

(60) S-1D F-8D (1287) PW-8 (872)

POND C-1D S-7D

(-140)

F-3D (1546)

PW-7 (1689) S-4D F-7D (2111)

C-2D (575)

P-14D (147)

F-6D F-5D P-2D (2388)

(689) (1512) (2384)

F-4D EXELON POND PW-15 (-22) PW-5 PW-6 PW-14 PW-4 F-2D (546)

F-1D

(-56) POND 20 0

20000 P-4D P-13D 5000 (217122) (38965) BL-17D P-5D (-126)

VB-2-6D RW-1 VB-3-4D PW-2 (44) RW-4 (2165)

MW-111D MW-112D RW-3 (790)

PW-3 RW-2 VB-3-9D VB-3-7D

(-66) (-111) PW-1 VB-2-5D MW-113D VB-2-9D (102) (19605) BL-16D (-205)

(4772)

(-65) (-91)

VB-2-7D BL-15D

(-53) VB-3-10D (-49) 20 VB-1-6D (108736) MW-105D VB-3 0 (41) VB-2-2D (-120)

(4037) BL-12D BL-14D VB-1-9D 50 (-35) (-91)

(3370) VB-1-7D BL-13D 00 BL-10D

(-116) 00 (7535) (9)

VB-1-3D VB-1-5D VB-1-8D BL-09D 50 BL-11D BL-20D (-27)

(19431) (22928) (10877) (20383) VB-2 (-117)

D-3D (5110)

VB-1-2D VB-1-4D D-2D (238) (7424)

VB-1 (-36)

D-1D VB-1-1D (-141) MW-106D

(-132) (-25)

LEGEND EXISTING FENCE LINE TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIES/LITER)

EXISTING PERIMETER DITCH LIMITS TRITIUM RESULTS 100,000 TO 200,000 BLOWDOWN LINE TRITIUM RESULTS 60,000 TO 100,000 PLANT PROPERTY LINE TRITIUM RESULTS 40,000 TO 60,000 BL-17D DEEP BLOWDOWN LINE SAMPLING LOCATION TRITIUM RESULTS 20,000 TO 40,000 VB-3 VACUUM BREAKER LOCATION TRITIUM RESULTS 10,000 TO 20,000 VB-3-7D DEEP VACUUM BREAKER SAMPLING LOCATION TRITIUM RESULTS 5,000 TO 10,000 MW-113D DEEP MONITORING WELL LOCATION TRITIUM RESULTS 200 TO 5,000 PW-5 PRIVATE WELL LOCATION TRITIUM RESULTS 0 TO 200 P-4D DEEP TEMPORARY WELL LOCATION NOTE:

PW-6P POND SAMPLING LOCATION BACKGROUND TRITIUM CONCENTRATION: 200 PCI/L DRINKING WATER STANDARD FOR TRITIUM: 20,000 PCI/L RW-2 DEEP RECOVERY WELL LOCATION TRITIUM DATA FOR SAMPLES COLLECTED THROUGH JANUARY 30, 2006. CONTOURS WERE GENERATED (2,484) TRITIUM RESULT IN GROUNDWATER USING LOG VALUES. figure 6.2 200 TRITIUM CONTOUR ESTIMATED TRITIUM RESULTS DEEP GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA023 MAR 21/2006

G-2 G-3 G-1 PW-11 0 200 600ft PW-13 SW-3 PW-12 PW-10 PW-9 S-2 S-1 S-3 PW-8 POND S-7 C-1 S-5 S-6 S-4 PW-7 V

C-2 SW-4 VB-4-1 MW-110 P-12 P-3 P-14 P-2 P-11 PW-6 PW-15 PW-5 PW-14 P-1 BL-19 PW-4 P-10 F-1 EXELON POND POND BL-18 P-9 SW-1 SW-2 BL-17 PW-2 P-8 P-6 P-4 P-7 P-5 VB-3-6 RW-1 VB-2-6 RW-4 RW-3 VB-3-5 MW-111 MW-113 VB-3-4 VB-3-7 MW-112 VB-2-5 VB-2-3 MW-109 PW-3 VB2-9 BL-16 PW-1 VB-3-3 VB-2-4 VB-2-8 MW-103 VB-3-1 VB-3-2 BL-15 VB-3-8 VB-2-7 VB-3-10 VB-2-2 MW-105 VB-3 VB-1-6 MW-104 BL-14 VB-1-9 BL-12 BL-13 VB-2-1 VB-1-7 BL-11 VB-1-8 MW-102 BL-10 VB-2 BL-09 EXELON NUCLEAR STATION VB-1-5 D-3 BL-08 VB-1-3 D-4 BL-07 VB-1-4 D-2 BL-06 MW-101 D-5 VB-1-2 D-1 BL-05 MW-107 BL-02 VB-1-1 BL-01 MW-108 BL-03 BL-04 MW-106 VB-1 LEGEND EXISTING FENCE LINE P-11 SHALLOW TEMPORARY WELL LOCATION BLOWDOWN LINE RW-3 SHALLOW RECOVERY WELL LOCATION figure 6.3 PLANT PROPERTY LINE SW-2 SURFACE WATER SAMPLING LOCATION BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION SAMPLE LOCATION MAXIMUM DETECTIONS OF TRITIUM IN THE VB-3 VACUUM BREAKER LOCATION BL-05 11/18/05 SAMPLE DATE SHALLOW GROUNDWATER ZONE THROUGH JANUARY 2006 VB-3-7 VACUUM BREAKER SAMPLING LOCATION 3H-Tritium 102 RESULT (pCi/L) EXELON GENERATION BRAIDWOOD STATION MW-105 SHALLOW MONITORING WELL LOCATION PARAMETER PW-5 PRIVATE WELL LOCATION 16841-11(012)GN-WA025 MAR 21/2006

G-2D PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 S-2D PW-8 S-1D F-8D S-7D C-1D F-3D PW-7 S-4D F-7D C-2D POND P-2D P-14D F-5D F-6D PW-6 PW-15 F-4D PW-5 PW-14 F-2D PW-4 EXELON POND F-1D POND P-13D P-4D BL-17D PW-2 P-5D VB2-9D VB-2-5D RW-2 MW-112D VB-2-6D VB-3-9D BL-16D VB-3-7D MW-111D MW-113D VB-3-4D PW-1 PW-3 VB-3-10D BL-15D VB1-6D VB-2-7D VB-2-2D MW-105D VB-3 BL-12D BL-14D VB1-9D BL-13D BL-20D VB-1-8D VB-1-7D BL-11D BL-10D VB-2 BL-09D EXELON NUCLEAR STATION VB1-5D VB1-3D D-3D VB1-4D VB1-2D D-2D D-1D VB-1 VB-1-1D MW-106D LEGEND EXISTING FENCE LINE P-4D DEEP TEMPORARY WELL LOCATION BLOWDOWN LINE RW-2 DEEP RECOVERY WELL LOCATION figure 6.4 PLANT PROPERTY LINE BL-17D DEEP BLOWDOWN LINE SAMPLING LOCATION SAMPLE LOCATION MAXIMUM DETECTIONS OF TRITIUM IN THE SAMPLE DATE VB-3 VACUUM BREAKER LOCATION BL-09D 3H-Tritium 12/23/05 23097 RESULT (pCi/L) DEEP GROUNDWATER ZONE THROUGH JANUARY 2006 VB-3-7D VACUUM BREAKER SAMPLING LOCATION PARAMETER EXELON GENERATION BRAIDWOOD STATION MW-113D DEEP MONITORING WELL LOCATION PW-5 PRIVATE WELL LOCATION 16841-11(012)GN-WA026 MAR 21/2006

A G-2 G-3 G-1 G-2D PW-11 PW-13 PW-12 PW-10 0 200 600ft PW-9 S-2 S-2D S-3 S-1 PW-8 S-1D F-8D POND S-7 C-1D S-7D C-1 F-3D S-5 S-4 S-6 PW-7 S-4D C-2D C-2 F-7D P-14 MW-110 P-12 P-2D P-3 P-14D F-6D F-5D P-2 P-11 PW-6 PW-15 F-4D BL-19 PW-5 PW-14 P-1 F-2D PW-4 P-10 F-1 EXELON POND F-1D POND BL-18 P-9 B'

B PW-2 P-8 P-7 P-6 P-5D P-5 P-13D P-4D P-4 VB-3-6 RW-1 BL-17D BL-17 RW-4 RW-3 MW-112 VB2-9D VB-2-6 RW-2 VB-3-5 MW-111 MW-112D VB-3-9D VB-3-4 BL-16D VB-3-7D MW-111D VB-2-6D VB-2-5 VB-2-3 MW-113D VB-3-4D VB-3-7 MW-109 PW-1 PW-3 VB2-9 VB-2-5D MW-113 BL-16 VB-2-4 VB-3-3 VB-3-8 VB-2-8 VB-2-7 MW-103 VB-3-1 VB-3-10D BL-15D VB-3-2 BL-15 VB1-6D VB-2-7D VB-3-10 VB-2-2D MW-105D VB-3 VB-1-6 MW-104 VB-2-2 BL-12D MW-105 BL-14D VB-1-9 VB1-9D VB-2-1 BL-14 BL-12 BL-13 BL-13D VB-1-7 VB-1-7D BL-20D VB-1-8 MW-102 BL-11D VB-1-8D VB-2 BL-11 BL-10 VB-1-3 BL-09 EXELON NUCLEAR STATION VB-1-5 VB1-3D VB1-5D D-3 D-4 BL-10D BL-08 BL-09D VB-1-4 VB1-4D D-2 D-3D D-2D BL-07 MW-101 VB1-2D D-5 VB-1-2 BL-06 MW-107 D-1D BL-05 VB-1-1 BL-01 D-1 BL-04 MW-106 VB-1 VB-1-1D BL-02 BL-03 MW-108 MW-106D A'

LEGEND EXISTING FENCE LINE MW-105 SHALLOW MONITORING WELL LOCATION BLOWDOWN LINE MW-113D DEEP MONITORING WELL LOCATION figure 6.5 PLANT PROPERTY LINE PW-5 PRIVATE WELL LOCATION BL-19 SHALLOW BLOWDOWN LINE SAMPLING LOCATION P-11 SHALLOW TEMPORARY WELL LOCATION HYDROGEOLOGIC PROFILE LOCATIONS BL-17D DEEP BLOWDOWN LINE SAMPLING LOCATION P-4D DEEP TEMPORARY WELL LOCATION EXELON GENERATION BRAIDWOOD STATION VB-3 VACUUM BREAKER LOCATION RW-3 SHALLOW RECOVERY WELL LOCATION VB-3-7 VACUUM BREAKER SAMPLING LOCATION RW-2 DEEP RECOVERY WELL LOCATION 16841-11(012)GN-WA006 MAR 21/2006

P-13D (OFFSET 77'E)

VB-3-1 (OFFSET 20'E) BL-12(OFFSET 40'W) 8" WATER MAKE UP LINE INTERSECTION A'

S-1 (OFFSET 138'W)

A MW-106 P-2 (OFFSET 59'E) VB-3-10 (OFFSET 88'E)

PW-9 (OFFSET 203'W)

BL-12D (OFFSET 40'W)

VACUUM PW-11 (OFFSET 92'E)

MW-106D 605 605 RW-2 (OFFSET 33'E) OF B-B' BREAKER #3 VB-3-10D (OFFSET 88'E)

S-1D (OFFSET 137'W) P-2D (OFFSET 59'E) 600 X 600 G-1 596.25 594.80 595 1/5/06 595 591.40 591.55 590.86 1/3/06 590.47 1/5/06 1/3/06 590.46 592.29 1/4/06 1/4/06 591.47 590.32 590.6 590.60 591.24 590.37 1/4/06 590 1/3/06 590 1/3/06 589.05 SW-2 1/25/06 1000 1/5/06 00 1/3/06 588.54 1/5/06 1/26/2006 2441 0 50 01/25/06 VB-3-10 VB-3-1 12076 MW-106 5959 01/03/06 -35 585 11/15/05 01/04/06 585 0 200 P-2 BL-12 S-1 2045 00 -39 83 12/06/05 01/03/06 20 01/03/06 580 580 G-1 133 40000 12/06/05 200 60000 VB-3-10D MW-106D P-2D 5000 575 10 108736 -25 575 2384 00 0

01/03/06 1000 00 01/04/06 0

01/03/06 BL-12D 2000

-35 P-13D 01/03/06 01/25/06 570 S-1D 570 217122 1287 01/26/06 565 565 560 560 SCALE: HORIZONTAL: 1"=400' 555 VERTICAL: 1"=40' 555 LEGEND 550 550 G-1 WELL ID TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIES/LITER)

TRITIUM RESULTS 10,000 TO 200,000 TRITIUM RESULTS 60,000 TO 100,000 590.32 GRONDWATER ELEVATION 1/3/06 TRITIUM RESULTS 40,000 TO 60,000 WELL TRITIUM RESULTS 20,000 TO 40,000 TRITIUM RESULTS 10,000 TO 20,000 figure 6.6 TRITIUM RESULTS 5,000 TO 10,000 SITE SPECIFIC HYDROGEOLOGIC PROFILE WELL SCREEN G-1 TRITIUM CONCENTRATION TRITIUM RESULTS 200 TO 5,000 JANUARY 2006 (A-A')

133 12/06/05 EXELON GENERATION BRAIDWOOD STATION TRITIUM RESULTS 0 TO 200 16841-11(012)GN-WA006 MAR 21/2006

MW-111 (OFFSET 51'S)

VB-2-3 (OFFSET 64'S)

MW-112 (OFFSET 44'S) VB-2-6 (OFFSET 43'S)

RW-3 (OFFSET 47'S)

MW-111D (OFFSET 51'S) 48" WATER MAKE UP LINE VB-3-6 (OFFSET 40'S)

MW-113 (OFFSET 78'S)

VB-2-6D (OFFSET 43'S)

VB-3-9D (OFFSET 30'S)

PW-1 (OFFSET 102'S) VB-3-5 (OFFSET 52'S)

B B' PW-2 (OFFSET 14'S)

MW-112D (OFFSET 44'S)

PW-3 (OFFSET 71'S)

MW-113D (OFFSET 78'S)

X RW-4 (OFFSET 49'S)

INTERSECTION OF A-A' 605 605 VB-2-5 (OFFSET 52'S)

VB-2-5D (OFFSET 52'S) P-13D (OFFSET 59'N) RW-1 (OFFSET 46'S) 600 600 595 MW-111 595

-78 593.50 590.80 590.94 590.80 590.91 590.90 1/4/06 1/3/06 1/5/06 1/5/06 1/3/06 1/3/06 1/5/06 591.30 590.85 590.66 1/5/06 590 590.65 590.70 1/3/06 590.86 1/3/06 590.52 590.82 590.77 590.98 591.13 590 1/4/06 1/9/06 MW-112 1/9/06 1/3/06 590.17 1/5/06 1/3/06 1/4/06 1/5/06

-127 1/3/06 1/4/06 VB-2-3 MW-113 585 3940 4008 4000 VB-3-5 585 0

11/15/05 1/3/06 VB-3-6 VB-2-6 95 VB-2-5 53572 1412 11/22/05 3834 11/22/05 1/3/06 1/3/06 580 20 500 580 MW-111D

-66 0 100000 1/9/06 2000 0 575 MW-112D VB-2-6D VB-2-5D MW-113D 575

-111 4772 VB-3-9D 44 102 1/9/06 1/3/06 19605 1/3/06 1/3/06 1/4/06 P-13D 570 217122 570 1/25/06 565 565 560 SCALE: HORIZONTAL: 1"=400' 560 VERTICAL: 1"=40' 555 LEGEND 555 G-1 WELL ID TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIES/LITER) 550 TRITIUM RESULTS 10,000 TO 200,000 550 TRITIUM RESULTS 60,000 TO 100,000 590.32 GRONDWATER ELEVATION 1/3/06 TRITIUM RESULTS 40,000 TO 60,000 WELL TRITIUM RESULTS 20,000 TO 40,000 TRITIUM RESULTS 10,000 TO 20,000 figure 6.7 TRITIUM RESULTS 5,000 TO 10,000 SITE SPECIFIC HYDROGEOLOGIC PROFILE WELL SCREEN G-1 TRITIUM CONCENTRATION TRITIUM RESULTS 200 TO 5,000 JANUARY 2006 (B-B')

133 12/06/05 EXELON GENERATION BRAIDWOOD STATION TRITIUM RESULTS 0 TO 200 16841-11(012)GN-WA006 MAR 21/2006

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 PW-8 PW-7 POND PW-5 PW-6 PW-15 PW-14 PW-4 EXELON POND POND PW-2 PW-3 PW-1 VB-3 EXELON NUCLEAR STATION VB-2 VB-1 LEGEND EXISTING FENCE LINE BLOWDOWN LINE SAMPLE LOCATION figure 6.8 PLANT PROPERTY LINE PW-1 11/30/05 SAMPLE DATE VB-3 VACUUM BREAKER LOCATION 3H-Tritium -26 RESULT (pCi/L) MAXIMUM DETECTIONS OF TRITIUM THROUGH JANUARY 2006 IN PRIVATE WELLS PW-5 PRIVATE WELL LOCATION PARAMETER EXELON GENERATION BRAIDWOOD STATION 16841-11(012)GN-WA024 MAR 21/2006

PW-11 0 200 600ft PW-13 PW-12 PW-10 PW-9 PW-8 PW-7 POND PW-6 PW-15 PW-5 PW-14 PW-4 EXELON POND 20000 POND PW-2 PW-1 PW-3 MODELED SOURCE VB-3 LOCATION EXELON NUCLEAR STATION VB-2 VB-1 LEGEND EXISTING FENCE LINE figure 7.1 BLOWDOWN LINE PLANT PROPERTY LINE GRAPHICAL PRESENTATION OF BIOSCREEN MODELING VB-3 VACUUM BREAKER LOCATION PRIVATE WELL LOCATION RESULTS AND LOCATION OF WATER SUPPLY WELLS PW-5 MAXIMUM EXTENT OF TRITIUM NOTE: PLUME REACHES STEADY EXELON GENERATION BRAIDWOOD STATION PLUME AT DRINKING WATER STATE IN 30 YEARS (2036).

STANDARD (20000 pCi/L) 16841-11(012)GN-WA029 MAR 21/2006

TABLE 4.1 Page 1 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 A-1 594.28 597.00 15.0 10 to 15 584.28 579.28 1 PVC4 2.72 A-1D 594.32 597.34 25.0 20 to 25 574.32 569.32 1 PVC 3.02 B-01 594.58 598.65 15.0 10 to 15 584.58 579.58 1 PVC 4.07 B-01D 594.69 596.53 28.0 23 to 28 571.69 566.69 1 PVC 1.84 BL-01 600.38 605.58 17.0 12 to 17 588.38 583.38 1 PVC 5.20 BL-02 600.16 604.84 14.5 9.5 to 14.5 590.66 585.66 1 PVC 4.68 BL-03 600.60 604.50 23.0 18 to 23 582.60 577.60 1 PVC 3.90 BL-04 599.76 601.91 14.5 10 to 15 589.76 584.76 1 PVC 2.15 BL-05 599.76 602.60 21.0 16 to 21 583.76 578.76 1 PVC 2.84 BL-06 597.74 601.83 15.0 10 to 15 587.74 582.74 1 PVC 4.09 BL-07 597.57 601.08 15.0 10 to 15 587.57 582.57 1 PVC 3.51 BL-08 598.53 602.29 15.0 10 to 15 588.53 583.53 1 PVC 3.76 BL-09 5 599.75 602.75 12.5 7.5 to 12.5 592.25 587.25 1 PVC 3.00 BL-09 599.60 602.49 22.0 16 to 21 583.60 578.60 1 PVC 2.89 BL-09D 599.65 600.36 29.0 24 to 29 575.65 570.65 1 PVC 0.71 BL-10 602.49 605.37 15.0 10 to 15 592.49 587.49 1 PVC 2.88 BL-10D 602.43 605.16 32.0 27 to 32 575.43 570.43 1 PVC 2.73 BL-11 597.47 600.65 15.0 10 to 15 587.47 582.47 1 PVC 3.18 BL-11D 597.34 599.09 28.0 23 to 28 574.34 569.34 1 PVC 1.75 BL-12 598.03 601.60 15.0 10 to 15 588.03 583.03 1 PVC 3.57 BL-12D 598.10 599.87 28.0 23 to 28 575.10 570.10 1 PVC 1.77 BL-13 598.07 601.37 15.0 10 to 15 588.07 583.07 1 PVC 3.30 BL-13D 598.05 600.82 24.5 19.5 to 24.5 578.55 573.55 1 PVC 2.77 BL-14 597.34 601.26 15.0 10 to 15 587.34 582.34 1 PVC 3.92 BL-14D 597.46 599.90 26.5 21.5 to 26.5 575.96 570.96 1 PVC 2.44 BL-15 597.29 600.98 15.0 10 to 15 587.29 582.29 1 PVC 3.69 BL-15D 597.54 598.50 24.0 19 to 24 578.54 573.54 1 PVC 0.96 BL-16 597.12 600.30 15.0 10 to 15 587.12 582.12 1 PVC 3.18 BL-16D 597.28 598.17 24.0 19 to 24 578.28 573.28 1 PVC 0.89 BL-17 597.01 597.62 14.5 9.5 to 14.5 587.51 582.51 1 PVC 0.61 BL-17D 597.01 598.11 25.0 19 to 24 578.01 573.01 1 PVC 1.10 BL-18 596.82 597.59 14.5 9.5 to 14.5 587.32 582.32 1 PVC 0.77 BL-18D 596.66 598.57 27.0 22 to 27 574.66 569.66 1 PVC 1.91 BL-19 594.94 595.55 9.0 4 to 9 590.94 585.94 1 PVC 0.61 BL-19D 595.06 596.93 28.2 23.2 to 28.2 571.86 566.86 1 PVC 1.87 BL-20D 596.89 600.45 29.0 23 to 28 573.89 568.89 1 PVC 3.56 CRA 016841 (12)

TABLE 4.1 Page 2 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 C-1 595.00 595.78 14.0 9 to 14 586.00 581.00 1 PVC 0.78 C-1D 595.00 595.87 25.0 19 to 24 576.00 571.00 1 PVC 0.87 C-2 606.94 610.91 15.5 10.5 to 15.5 596.44 591.44 1 PVC 3.97 C-2D 606.82 609.03 27.5 22.5 to 27.5 584.32 579.32 1 PVC 2.21 D-1 599.64 603.69 15.0 10 to 15 589.64 584.64 1 PVC 4.05 D-1D 599.82 603.77 27.0 22 to 27 577.82 572.82 1 PVC 3.95 D-2 598.78 601.92 12.0 7 to 12 591.78 586.78 1 PVC 3.14 D-2D 598.65 601.47 28.0 22 to 27 576.65 571.65 1 PVC 2.82 D-3 599.00 602.48 12.0 7 to 12 592.00 587.00 1 PVC 3.48 D-3D 598.91 602.22 28.0 22 to 27 576.91 571.91 1 PVC 3.31 D-4 598.48 602.55 15.0 10 to 15 588.48 583.48 1 PVC 4.07 D-5 598.58 602.27 12.0 7 to 12 591.58 586.58 1 PVC 3.69 F-1 595.27 596.25 14.0 9 to 14 586.27 581.27 1 PVC 0.98 F-1D 595.27 596.19 25.0 19 to 24 576.27 571.27 1 PVC 0.92 F-2D 594.05 597.26 25.0 20 to 25 574.05 569.05 1 PVC 3.21 F-3D 594.59 597.36 25.0 20 to 25 574.59 569.59 1 PVC 2.77 F-4D 595.57 599.59 29.5 24.5 to 29.5 571.07 566.07 1 PVC 4.02 F-5D 593.38 595.96 27.0 22 to 27 571.38 566.38 1 PVC 2.58 F-6D 595.05 597.28 27.5 22.5 to 27.5 572.55 567.55 1 PVC 2.23 F-7D 594.38 596.37 28.0 23 to 28 571.38 566.38 1 PVC 1.99 F-8D 594.60 598.42 26.0 21 to 26 573.60 568.60 1 PVC 3.82 G-1 590.70 595.35 14.5 9.5 to 14.5 581.20 576.20 1 PVC 4.65 G-2 590.24 590.82 14.5 9.5 to 14.5 580.74 575.74 1 PVC 0.58 G-2D 590.05 590.65 25.0 19 to 24 571.05 566.05 1 PVC 0.60 G-3 592.34 592.93 14.5 9.5 to 14.5 582.84 577.84 1 PVC 0.59 MW-101 599.49 602.77 10.0 5 to 10 594.49 589.49 2 PVC 3.28 MW-102 602.42 605.70 11.0 6 to 11 596.42 591.42 2 PVC 3.28 MW-103 595.72 598.84 8.0 3 to 8 592.72 587.72 2 PVC 3.12 MW-104 596.60 598.80 8.0 3 to 8 593.60 588.60 2 PVC 2.20 MW-105 597.29 600.74 16.0 5 to 15 592.29 582.29 2 PVC 3.45 MW-105D 597.22 598.20 24.0 19 to 24 578.22 573.22 1 PVC 0.98 MW-106 599.60 602.73 16.0 5 to 15 594.60 584.60 2 PVC 3.13 MW-106D 599.70 601.81 27.0 22 to 27 577.70 572.70 1 PVC 2.11 MW-107 599.85 603.24 16.0 5 to 15 594.85 584.85 2 PVC 3.39 MW-108 599.76 603.10 16.0 5 to 15 594.76 584.76 2 PVC 3.34 MW-109 598.81 601.23 16.0 5 to 15 593.81 583.81 2 PVC 2.42 CRA 016841 (12)

TABLE 4.1 Page 3 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 MW-110 604.01 607.27 20.0 9.5 to 19.5 594.51 584.51 2 PVC 3.26 MW-111 603.29 607.20 16.0 5.5 to 15.5 597.79 587.79 2 PVC 3.91 MW-111D 603.17 605.05 26.5 21.5 to 26.5 581.67 576.67 1 PVC 1.88 MW-112 598.57 602.62 16.0 5.5 to 15.5 593.07 583.07 2 PVC 4.05 MW-112D 598.61 600.85 26.0 21 to 26 577.61 572.61 1 PVC 2.24 MW-113 596.10 599.77 16.0 5.5 to 15.5 590.60 580.60 2 PVC 3.67 MW-113D 596.14 596.90 25.0 19 to 24 577.14 572.14 1 PVC 0.76 P-1 594.90 595.59 14.5 9.5 to 14.5 585.40 580.40 1 PVC 0.69 P-2 595.65 596.27 14.5 9.5 to 14.5 586.15 581.15 1 PVC 0.62 P-2D 595.88 596.55 24.0 18.5 to 23.5 577.38 572.38 1 PVC 0.67 P-3 595.69 596.26 14.5 9.5 to 14.5 586.19 581.19 1 PVC 0.57 P-4 595.69 597.14 14.5 9.5 to 14.5 586.19 581.19 1 PVC 1.45 P-4D 596.46 599.22 27.0 22 to 27 574.46 569.46 1 PVC 2.76 P-5 596.34 597.06 15.0 10 to 15 586.34 581.34 1 PVC 0.72 P-5D 596.34 599.37 27.0 22 to 27 574.34 569.34 1 PVC 3.03 P-6 597.57 597.85 14.5 9.5 to 14.5 588.07 583.07 1 PVC 0.28 P-7 599.77 600.24 14.5 9.5 to 14.5 590.27 585.27 1 PVC 0.47 P-8 595.49 596.24 14.5 9.5 to 14.5 585.99 580.99 1 PVC 0.75 P-9 598.55 599.19 14.5 9.5 to 14.5 589.05 584.05 1 PVC 0.64 P-10 596.08 596.58 14.5 9.5 to 14.5 586.58 581.58 1 PVC 0.50 P-11 595.19 596.23 14.5 9.5 to 14.5 585.69 580.69 1 PVC 1.04 P-12 595.56 596.13 14.5 9.5 to 14.5 586.06 581.06 1 PVC 0.57 P-13D 596.11 598.76 27.0 22 to 27 574.11 569.11 1 PVC 2.65 P-14 596.52 599.14 15.5 10.5 to 15.5 586.02 581.02 1 PVC 2.62 P-14D 596.65 598.50 28.0 23 to 28 573.65 568.65 1 PVC 1.85 PS-1 543.95 546.13 12.0 6 to 11 537.95 532.95 1 PVC 2.18 PS-2 542.12 546.76 11.0 5 to 10 537.12 532.12 1 PVC 4.64 PS-3 547.16 550.09 12.0 6 to 11 541.16 536.16 1 PVC 2.93 PS-4 547.78 548.90 13.75 8.75 to 13.75 539.03 534.03 1 PVC 1.12 PS-5 548.41 550.24 13.0 8 to 13 540.41 535.41 1 PVC 1.83 PS-6 543.94 547.40 12.0 7 to 12 536.94 531.94 1 PVC 3.46 RW-1 596.68 599.36 28.0 5 to 25 591.68 571.68 4 PVC 2.68 RW-2 596.59 599.30 25.0 4 to 24 592.59 572.59 4 PVC 2.71 RW-3 596.24 599.19 24.0 4 to 24 592.24 572.24 4 PVC 2.95 RW-4 596.31 598.77 24.0 4 to 24 592.31 572.31 4 PVC 2.46 S-1 594.99 595.60 14.5 9.5 to 14.5 585.49 580.49 1 PVC 0.61 CRA 016841 (12)

TABLE 4.1 Page 4 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 S-1D 594.94 596.92 28.0 22 to 27 572.94 567.94 1 PVC 1.98 S-2 592.72 593.32 14.5 9.5 to 14.5 583.22 578.22 1 PVC 0.60 S-2D 592.72 593.98 24.0 18.5 to 23.5 574.22 569.22 1 PVC 1.26 S-3 592.65 593.37 14.5 9.5 to 14.5 583.15 578.15 1 PVC 0.72 S-4 594.23 594.63 14.5 9.5 to 14.5 584.73 579.73 1 PVC 0.40 S-4D 593.91 596.67 25.5 19.5 to 24.5 574.41 569.41 1 PVC 2.76 S-5 592.76 593.44 14.5 9.5 to 14.5 583.26 578.26 1 PVC 0.68 S-6 594.99 595.57 14.5 9.5 to 14.5 585.49 580.49 1 PVC 0.58 S-7 593.54 594.73 13.6 8.6 to 13.6 584.94 579.94 1 PVC 1.19 S-7D 593.50 596.53 27.5 22.5 to 27.5 571.00 566.00 1 PVC 3.03 VB-1-1 602.14 605.62 15.0 10 to 15 592.14 587.14 1 PVC 3.48 VB-1-1D 602.14 604.52 32.0 27 to 32 575.14 570.14 1 PVC 2.38 VB-1-2 599.94 604.65 15.0 10 to 15 589.94 584.94 1 PVC 4.71 VB-1-2D 600.02 601.89 28.0 23 to 28 577.02 572.02 1 PVC 1.87 VB-1-3 599.64 603.61 15.0 10 to 15 589.64 584.64 1 PVC 3.97 VB-1-3D 599.55 601.95 27.5 22.5 to 27.5 577.05 572.05 1 PVC 2.40 VB-1-4 599.32 601.50 15.0 10 to 15 589.32 584.32 1 PVC 2.18 VB-1-4D 599.93 602.01 28.0 23 to 28 576.93 571.93 1 PVC 2.08 VB-1-5 600.17 603.85 15.0 10 to 15 590.17 585.17 1 PVC 3.68 VB-1-5D 600.26 602.29 28.0 23 to 28 577.26 572.26 1 PVC 2.03 VB-1-6 602.16 605.34 15.0 10 to 15 592.16 587.16 1 PVC 3.18 VB-1-6D 601.86 605.53 28.0 22 to 27 579.86 574.86 1 PVC 3.67 VB-1-7 600.60 603.62 15.0 10 to 15 590.60 585.60 1 PVC 3.02 VB-1-7D 600.48 602.80 26.2 21.2 to 26.2 579.28 574.28 1 PVC 2.32 VB-1-8 600.32 603.36 15.0 10 to 15 590.32 585.32 1 PVC 3.04 VB-1-8D 600.15 602.49 26.0 21 to 26 579.15 574.15 1 PVC 2.34 VB-1-9 598.92 601.86 15.0 10 to 15 588.92 583.92 1 PVC 2.94 VB-1-9D 598.69 601.61 27.0 22 to 27 576.69 571.69 1 PVC 2.92 VB-2-1 601.27 605.71 15.0 10 to 15 591.27 586.27 1 PVC 4.44 VB-2-2 596.82 600.16 15.0 10 to 15 586.82 581.82 1 PVC 3.34 VB-2-2D 596.49 598.95 30.5 24.5 to 29.5 571.99 566.99 1 PVC 2.46 VB-2-3 595.95 600.16 15.0 10 to 15 585.95 580.95 1 PVC 4.21 VB-2-4 596.08 600.82 15.0 10 to 15 586.08 581.08 1 PVC 4.74 VB-2-5 595.76 599.82 15.0 10 to 15 585.76 580.76 1 PVC 4.06 VB-2-5D 595.76 596.78 25.0 19 to 24 576.76 571.76 1 PVC 1.02 VB-2-6 596.01 601.44 15.0 10 to 15 586.01 581.01 1 PVC 5.43 CRA 016841 (12)

TABLE 4.1 Page 5 of 5

SUMMARY

OF PERMANENT AND TEMPORARY MONITORING WELL SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Ground Top of Riser Boring Screen Screen Top Screen Bottom Well Stickup Well Surface Elevation Total Depth Interval Elevation Elevation Diameter Well Height Number (NGVD) 1 (NGVD) (ft BGS) 2 (ft BGS) (NGVD) (NGVD) (inches) Material (ft AGS) 3 VB-2-6D 596.01 596.77 25.0 19 to 24 577.01 572.01 1 PVC 0.76 VB-2-7 600.51 602.04 15.0 10 to 15 590.51 585.51 1 PVC 1.53 VB-2-7D 600.51 602.28 26.0 20 to 25 580.51 575.51 1 PVC 1.77 VB-2-8 598.18 599.05 15.0 10 to 15 588.18 583.18 1 PVC 0.87 VB-2-9 596.31 599.48 14.0 9 to 14 587.31 582.31 1 PVC 3.17 VB-2-9D 596.26 599.93 28.0 21 to 26 575.26 570.26 1 PVC 3.67 VB-3-1 596.38 600.99 15.0 10 to 15 586.38 581.38 1 PVC 4.61 VB-3-2 596.49 601.51 15.0 10 to 15 586.49 581.49 1 PVC 5.02 VB-3-3 596.27 600.03 15.0 10 to 15 586.27 581.27 1 PVC 3.76 VB-3-4 596.18 601.37 15.0 10 to 15 586.18 581.18 1 PVC 5.19 VB-3-4D 596.18 600.82 25.0 20 to 25 576.18 571.18 1 PVC 4.64 VB-3-5 595.94 599.24 15.0 10 to 15 585.94 580.94 1 PVC 3.30 VB-3-6 595.89 599.18 15.0 10 to 15 585.89 580.89 1 PVC 3.29 VB-3-7 596.24 599.49 12.0 7 to 12 589.24 584.24 1 PVC 3.25 VB-3-7D 596.24 597.04 25.0 19 to 24 577.24 572.24 1 PVC 0.80 VB-3-8 596.44 599.51 12.0 7 to 12 589.44 584.44 1 PVC 3.07 VB-3-9D 595.68 596.62 25.0 19.5 to 24.5 576.18 571.18 1 PVC 0.94 VB-3-10 596.43 599.28 13.0 8 to 13 588.43 583.43 1 PVC 2.85 VB-3-10D 596.49 598.44 23.5 18.5 to 23.5 577.99 572.99 1 PVC 1.95 1

NGVD - National Geodetic Vertical datum 2

ft BGS - feet below ground surface 3

FT AGS - feet above ground surface 4

PVC - polyvinyl chloride 5

Well was abandoned and replaced Survey data incomplete CRA 016841 (12)

TABLE 4.2 Page 1 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

A-1 1/10/2006 597.00 9.01 587.99 A-1 1/11/2006 597.00 9.01 587.99 A-1D 1/10/2006 597.34 9.33 588.01 A-1D 1/11/2006 597.34 9.33 588.01 BL-01 11/15/2005 605.58 13.43 592.15 BL-01 1/5/2006 605.58 13.09 592.49 BL-02 11/15/2005 604.84 12.92 591.92 BL-02 1/5/2006 604.84 12.59 592.25 BL-03 11/15/2005 604.50 13.34 591.16 BL-03 1/5/2006 604.50 12.91 591.59 BL-04 11/15/2005 601.91 10.93 590.98 BL-04 1/5/2006 601.91 10.50 591.41 BL-05 11/15/2005 602.60 11.77 590.83 BL-05 1/5/2006 602.60 11.39 591.21 BL-06 11/15/2005 601.83 11.00 590.83 BL-06 1/5/2006 601.83 10.63 591.20 BL-07 11/15/2005 601.08 10.28 590.80 BL-07 1/5/2006 601.08 10.11 590.97 BL-08 11/15/2005 602.29 11.40 590.89 BL-08 1/5/2006 602.29 11.13 591.16 BL-09 11/15/2005 602.49 11.82 590.67 BL-09 12/21/2005 602.49 11.40 591.09 BL-09 12/23/2005 602.49 11.31 591.18 BL-09 1/5/2006 602.49 11.18 591.31 BL-09 1/11/2006 602.49 11.01 591.48 BL-09 2/1/2006 602.49 10.65 591.84 BL-09 2/10/2006 602.49 10.44 592.05 BL-09 2/15/2006 602.49 10.35 592.14 BL-09D 12/21/2005 600.36 9.40 590.96 BL-09D 12/23/2005 600.36 9.35 591.01 BL-09D 1/5/2006 600.36 9.21 591.15 BL-09D 1/11/2006 600.36 9.08 591.28 BL-09D 2/1/2006 600.36 8.68 591.68 BL-09D 2/10/2006 600.36 8.48 591.88 BL-09D 2/15/2006 600.36 8.37 591.99 BL-10 11/15/2005 605.37 14.29 591.08 BL-10 1/4/2006 605.37 14.03 591.34 BL-10D 12/15/2005 605.16 14.89 590.27 BL-10D 1/4/2006 605.16 13.81 591.35 BL-11 11/15/2005 600.65 9.70 590.95 BL-11 1/3/2006 600.65 9.41 591.24 BL-11D 12/15/2005 599.09 7.82 591.27 BL-11D 1/3/2006 599.09 7.56 591.53 BL-12 11/15/2005 601.60 10.41 591.19 BL-12 1/3/2006 601.60 10.05 591.55 BL-12D 12/15/2005 599.87 8.54 591.33 CRA 016841 (12)

TABLE 4.2 Page 2 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

BL-12D 1/3/2006 599.87 8.40 591.47 BL-13 11/15/2005 601.37 10.27 591.10 BL-13 1/3/2006 601.37 9.94 591.43 BL-13D 12/15/2005 600.82 9.39 591.43 BL-13D 1/3/2006 600.82 9.17 591.65 BL-14 11/15/2005 601.26 9.91 591.35 BL-14 1/3/2006 601.26 9.65 591.61 BL-14D 12/15/2005 597.46 8.49 588.97 BL-14D 1/3/2006 597.46 8.26 589.20 BL-15 11/15/2005 600.98 9.98 591.00 BL-15 1/3/2006 600.98 9.57 591.41 BL-15D 12/16/2005 598.50 6.20 592.30 BL-15D 1/3/2006 598.50 6.92 591.58 BL-16 11/15/2005 600.30 9.40 590.90 BL-16 1/3/2006 600.30 9.05 591.25 BL-16D 12/16/2005 598.17 7.10 591.07 BL-16D 1/3/2006 598.17 6.92 591.25 BL-17 12/1/2005 597.62 6.47 591.15 BL-17 12/5/2005 597.62 6.50 591.12 BL-17 1/3/2006 597.62 6.37 591.25 BL-17D 12/12/2005 598.11 7.21 590.90 BL-17D 1/3/2006 598.11 6.80 591.31 BL-18 12/1/2005 597.59 6.71 590.88 BL-18 1/3/2006 597.59 6.52 591.07 BL-19 12/1/2005 595.55 5.04 590.51 BL-19 1/3/2006 595.55 4.93 590.62 BL-20D 12/21/2005 600.45 9.40 591.05 BL-20D 12/23/2005 600.45 9.56 590.89 BL-20D 1/4/2006 600.45 9.16 591.29 C-1 12/12/2005 595.78 7.21 588.57 C-1 1/3/2006 595.78 6.78 589.00 C-1D 12/12/2005 595.87 7.35 588.52 C-1D 1/3/2006 595.87 6.79 589.08 C-2 1/24/2006 610.91 9.00 601.91 C-2 2/1/2006 610.91 8.50 602.41 C-2 2/10/2006 610.91 8.56 602.35 C-2 2/15/2006 610.91 8.70 602.21 C-2D 1/24/2006 609.03 7.09 601.94 C-2D 2/1/2006 609.03 6.75 602.28 C-2D 2/10/2006 609.03 6.76 602.27 C-2D 2/15/2006 609.03 6.90 602.13 D-1 12/6/2005 603.69 12.10 591.59 D-1 1/4/2006 603.69 11.90 591.79 D-1D 12/22/2005 603.77 12.10 591.67 D-1D 12/23/2005 603.77 12.04 591.73 D-1D 1/4/2006 603.77 12.00 591.77 CRA 016841 (12)

TABLE 4.2 Page 3 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

D-2 12/5/2005 601.92 10.52 591.40 D-2 1/4/2006 601.92 10.31 591.61 D-2D 12/22/2005 601.47 9.95 591.52 D-2D 1/4/2006 601.47 9.76 591.71 D-3 12/2/2005 602.48 11.05 591.43 D-3 1/4/2006 602.48 10.85 591.63 D-3D 12/23/2005 602.22 10.71 591.51 D-3D 1/4/2006 602.22 10.60 591.62 D-4 1/5/2006 602.55 11.09 591.46 D-5 12/2/2005 602.27 10.86 591.41 D-5 1/5/2006 602.27 10.57 591.70 F-1 12/12/2005 596.25 7.40 588.85 F-1 1/3/2006 596.25 7.19 589.06 F-1D 12/12/2005 596.19 7.35 588.84 F-1D 1/3/2006 596.19 7.10 589.09 F-2D 1/9/2006 597.26 7.26 590.00 F-3D 1/9/2006 597.36 8.57 588.79 F-3D 1/12/2006 597.36 8.67 588.69 F-4D 1/24/2006 599.59 10.87 588.72 F-5D 1/24/2006 595.96 6.65 589.31 F-6D 1/24/2006 597.28 9.26 588.02 F-7D 1/24/2006 596.37 8.48 587.89 F-8D 1/24/2006 598.42 9.70 588.72 G-1 12/6/2005 595.35 5.55 589.80 G-1 1/5/2006 595.35 5.03 590.32 G-2 12/6/2005 590.83 5.31 585.52 G-2 1/5/2006 590.83 4.81 586.02 G-2D 1/26/2006 590.65 3.65 587.00 G-3 12/6/2005 592.93 7.25 585.68 G-3 1/5/2006 592.93 6.85 586.08 MW-101 7/28/2005 602.77 12.25 590.52 MW-101 8/15/2005 602.77 11.01 591.76 MW-101 9/30/2005 602.77 11.49 591.28 MW-101 11/11/2005 602.77 11.67 591.10 MW-101 11/15/2005 602.77 11.60 591.17 MW-101 1/5/2006 602.77 11.35 591.42 MW-102 7/28/2005 605.70 13.17 592.53 MW-102 8/15/2005 605.70 13.78 591.92 MW-102 11/11/2005 605.70 13.79 591.91 MW-102 11/18/2005 605.70 13.79 591.91 MW-102 1/5/2006 605.70 13.78 591.92 MW-103 8/15/2005 598.84 6.90 591.94 MW-103 10/17/2005 598.84 7.78 591.06 MW-103 11/11/2005 598.84 7.81 591.03 MW-103 11/15/2005 598.84 7.70 591.14 MW-103 1/5/2006 598.84 7.75 591.09 CRA 016841 (12)

TABLE 4.2 Page 4 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

MW-104 7/28/2005 598.80 7.67 591.13 MW-104 8/15/2005 598.80 9.72 589.08 MW-104 11/11/2005 598.80 8.77 590.03 MW-104 11/18/2005 598.80 8.75 590.05 MW-104 1/5/2006 598.80 8.59 590.21 MW-105 7/28/2005 600.74 7.82 592.92 MW-105 8/15/2005 600.74 8.38 592.36 MW-105 9/30/2005 600.74 9.50 591.24 MW-105 10/17/2005 600.74 9.19 591.55 MW-105 11/11/2005 600.74 9.41 591.33 MW-105 11/15/2005 600.74 9.30 591.44 MW-105 1/4/2006 600.74 6.05 594.69 MW-105 1/5/2006 600.74 6.05 594.69 MW-105D 12/15/2005 598.20 6.76 591.44 MW-105D 12/16/2005 598.20 6.81 591.39 MW-105D 1/4/2006 598.20 6.48 591.72 MW-106 7/28/2005 602.73 9.13 593.60 MW-106 8/15/2005 602.73 9.66 593.07 MW-106 11/11/2005 602.73 10.71 592.02 MW-106 11/14/2005 602.73 10.82 592.31 MW-106 1/4/2006 602.73 10.42 591.91 MW-106 1/5/2006 602.73 6.48 596.25 MW-106D 12/16/2005 601.81 9.84 591.97 MW-106D 1/4/2006 601.81 9.52 592.29 MW-107 7/28/2005 603.24 9.62 593.62 MW-107 8/15/2005 603.24 9.93 593.31 MW-107 9/30/2005 603.24 10.41 592.83 MW-107 10/17/2005 603.24 10.55 592.69 MW-107 11/11/2005 603.24 10.70 592.54 MW-107 11/15/2005 603.24 10.71 592.53 MW-107 1/5/2006 603.24 10.42 592.82 MW-108 7/28/2005 603.10 10.72 592.38 MW-108 8/15/2005 603.10 10.89 592.21 MW-108 9/30/2005 603.10 11.31 591.79 MW-108 10/17/2005 603.10 11.42 591.68 MW-108 11/11/2005 603.10 11.24 591.86 MW-108 11/15/2005 603.10 11.18 591.92 MW-108 1/5/2006 603.10 12.90 590.20 MW-109 7/28/2005 601.23 9.70 591.53 MW-109 8/15/2005 601.23 9.91 591.32 MW-109 11/11/2005 601.23 10.58 590.65 MW-109 1/5/2006 601.23 10.41 590.82 MW-110 11/11/2005 607.27 19.16 588.11 MW-110 11/14/2005 607.27 19.28 587.99 MW-110 11/15/2005 607.27 19.19 588.08 MW-110 1/3/2006 607.27 19.46 587.81 CRA 016841 (12)

TABLE 4.2 Page 5 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

MW-110 1/4/2006 607.27 19.46 587.81 MW-111 11/11/2005 607.20 16.78 590.42 MW-111 11/15/2005 607.20 16.74 590.46 MW-111 1/4/2006 607.20 16.55 590.65 MW-111D 1/9/2006 605.05 14.35 590.70 MW-112 11/11/2005 602.62 12.19 590.43 MW-112 11/15/2005 602.62 12.13 590.49 MW-112 1/3/2006 602.62 11.77 590.85 MW-112 1/4/2006 602.62 11.77 590.85 MW-112D 1/9/2006 600.85 9.89 590.96 MW-113 11/11/2005 599.77 8.87 590.90 MW-113 11/15/2005 599.77 8.75 591.02 MW-113 12/5/2005 599.77 8.89 590.88 MW-113 1/3/2006 599.77 8.97 590.80 MW-113D 12/14/2005 596.90 6.12 590.78 MW-113D 1/3/2006 596.90 6.13 590.77 P-1 12/1/2005 595.59 5.08 590.51 P-1 1/5/2006 595.59 5.02 590.57 P-2 12/2/2005 596.27 5.95 590.32 P-2 1/3/2006 596.27 5.81 590.46 P-2 1/4/2006 596.27 5.81 590.46 P-2D 12/12/2005 596.55 6.26 590.29 P-2D 1/3/2006 596.55 6.08 590.47 P-2D 1/4/2006 596.55 6.08 590.47 P-3 12/2/2005 596.26 6.08 590.18 P-3 1/5/2006 596.26 5.91 590.35 P-4 12/1/2005 597.14 6.41 590.73 P-4 12/6/2005 597.14 6.50 590.64 P-4 1/3/2006 597.14 6.41 590.73 P-4 1/11/2006 597.14 6.31 590.83 P-4 1/18/2006 597.14 6.28 590.86 P-4 1/25/2006 597.14 6.21 590.93 P-4 2/1/2006 597.14 5.95 591.19 P-4 2/10/2006 597.14 5.98 591.16 P-4 2/15/2006 597.14 6.00 591.14 P-4D 12/23/2005 599.22 8.68 590.54 P-4D 1/3/2006 599.22 8.63 590.59 P-4D 1/11/2006 599.22 8.55 590.67 P-4D 1/18/2006 599.22 8.50 590.72 P-4D 1/25/2006 599.22 8.48 590.74 P-4D 2/1/2006 599.22 8.06 591.16 P-4D 2/10/2006 599.22 8.20 591.02 P-4D 2/15/2006 599.22 8.28 590.94 P-4D 2/22/2006 599.22 8.16 591.06 P-5 12/1/2005 597.06 6.48 590.58 P-5 1/3/2006 597.06 6.45 590.61 CRA 016841 (12)

TABLE 4.2 Page 6 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

P-5D 12/23/2005 599.37 10.22 589.15 P-5D 1/3/2006 599.37 8.91 590.46 P-6 12/1/2005 597.85 7.30 590.55 P-6 1/5/2006 597.85 7.41 590.44 P-6 1/18/2006 597.85 6.18 591.67 P-7 12/1/2005 600.24 9.58 590.66 P-7 1/5/2006 600.24 9.52 590.72 P-8 12/1/2005 596.24 5.63 590.61 P-8 12/6/2005 596.24 5.74 590.50 P-8 1/5/2006 596.24 5.59 590.65 P-9 12/5/2005 599.19 8.75 590.44 P-9 1/5/2006 599.19 8.44 590.75 P-10 12/5/2005 596.58 6.54 590.04 P-10 1/5/2006 596.58 6.23 590.35 P-11 12/5/2005 596.23 6.55 589.68 P-11 1/5/2006 596.23 6.20 590.03 P-12 12/5/2005 596.13 6.79 589.34 P-12 1/5/2006 596.13 6.49 589.64 P-13D 12/23/2005 598.76 8.34 590.42 P-13D 1/3/2006 598.76 8.25 590.51 P-13D 1/11/2006 598.76 5.26 593.50 P-13D 1/18/2006 598.76 5.20 593.56 P-13D 1/25/2006 598.76 8.16 590.60 P-13D 2/1/2006 598.76 7.90 590.86 P-13D 2/10/2006 598.76 7.98 590.78 P-13D 2/15/2006 598.76 8.00 590.76 P-13D 2/22/2006 598.76 8.02 590.74 P-14 1/24/2006 599.14 6.40 592.74 P-14D 1/24/2006 598.50 7.89 590.61 PS-1 12/22/2005 546.13 6.77 539.36 PS-1 1/4/2006 546.13 7.88 538.25 PS-2 12/22/2005 546.76 10.21 536.55 PS-2 1/4/2006 546.76 9.65 537.11 PS-3 12/22/2005 550.09 10.65 539.44 PS-3 12/23/2005 550.09 14.15 535.94 PS-3 1/4/2006 550.09 14.06 536.03 PS-4 1/9/2006 548.90 10.90 538.00 PS-5 1/10/2006 550.24 10.91 539.33 PS-6 1/10/2006 547.40 7.51 539.89 RW-1 12/1/2005 599.36 7.42 591.94 RW-1 1/5/2006 599.36 8.23 591.13 RW-2 12/1/2005 599.30 8.68 590.62 RW-2 1/5/2006 599.30 8.44 590.86 RW-3 12/2/2005 599.19 8.48 590.71 RW-3 1/5/2006 599.19 8.37 590.82 RW-4 12/2/2005 598.77 8.12 590.65 CRA 016841 (12)

TABLE 4.2 Page 7 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

RW-4 1/5/2006 598.77 7.97 590.80 S-1 12/5/2005 595.60 7.50 588.10 S-1 1/5/2006 595.60 7.06 588.54 S-1D 1/26/2006 596.92 7.87 589.05 S-2 12/5/2005 593.32 5.22 588.10 S-2 1/3/2006 593.32 4.68 588.64 S-2 1/5/2006 593.32 4.70 588.62 S-2 2/1/2006 593.32 3.80 589.52 S-2 2/10/2006 593.32 3.98 589.34 S-2 2/15/2006 593.32 4.04 589.28 S-2 2/22/2006 593.32 4.08 589.24 S-2D 12/12/2005 593.98 6.14 587.84 S-2D 1/3/2006 593.98 5.30 588.68 S-2D 1/5/2006 593.98 5.35 588.62 S-2D 2/1/2006 593.98 4.37 589.61 S-2D 2/10/2006 593.98 4.56 589.42 S-2D 2/15/2006 593.98 4.62 589.36 S-2D 2/22/2006 593.98 4.65 589.33 S-3 12/5/2005 593.37 5.29 588.08 S-3 1/5/2006 593.37 4.78 588.59 S-4 12/5/2005 594.63 5.69 588.94 S-4 1/5/2006 594.63 5.25 589.38 S-4D 1/26/2006 596.67 7.75 588.92 S-5 12/5/2005 593.44 4.25 589.19 S-5 1/5/2006 593.44 3.85 589.59 S-6 12/5/2005 595.57 6.72 588.85 S-6 1/5/2006 595.57 6.31 589.26 S-7 1/24/2006 594.73 4.98 589.75 S-7D 1/24/2006 596.53 6.80 589.73 SG-1 8/15/2005 594.08 0.19 593.89 SG-2 8/15/2005 594.85 0.15 594.70 SG-3 8/15/2005 594.51 0.00 594.51 SG-A 2/1/2006 589.78 1.39 591.17 SG-A 2/10/2006 589.78 1.40 591.18 SG-A 2/15/2006 589.78 1.20 590.98 SG-B 1/25/2006 589.75 1.00 590.75 SG-B 2/1/2006 589.75 1.10 590.85 SG-B 2/10/2006 589.75 1.19 590.94 SG-B 2/15/2006 589.75 1.19 590.94 SG-C 1/25/2006 585.93 1.01 586.94 SG-C 2/1/2006 585.93 1.11 587.04 SG-C 2/10/2006 585.93 1.21 587.14 SG-C 2/15/2006 585.93 1.50 587.43 VB-1-1D 12/16/2005 604.52 12.34 592.18 VB-1-1D 1/4/2006 604.52 12.30 592.22 VB-1-2 11/15/2005 604.65 12.75 591.90 CRA 016841 (12)

TABLE 4.2 Page 8 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

VB-1-2 1/5/2006 604.65 12.39 592.26 VB-1-2D 1/10/2006 601.89 9.40 592.49 VB-1-2D 1/13/2006 601.89 9.40 592.49 VB-1-3 11/15/2005 603.61 11.97 591.64 VB-1-3 1/5/2006 603.61 11.72 591.89 VB-1-3D 1/10/2006 601.95 9.67 592.28 VB-1-3D 1/13/2006 601.95 9.65 592.30 VB-1-4 11/15/2005 601.50 10.62 590.88 VB-1-4 1/5/2006 601.50 10.31 591.19 VB-1-4D 1/13/2006 602.01 8.90 593.11 VB-1-5 11/15/2005 603.85 12.52 591.33 VB-1-5 1/5/2006 603.85 12.21 591.64 VB-1-5D 1/10/2006 602.29 10.30 593.55 VB-1-5D 1/13/2006 602.29 10.29 592.00 VB-1-6 11/22/2005 605.34 14.38 590.96 VB-1-6 1/5/2006 605.34 14.11 591.23 VB-1-6D 1/10/2006 605.53 14.20 591.33 VB-1-6D 1/13/2006 605.53 14.30 591.23 VB-1-7 11/22/2005 603.62 12.44 591.18 VB-1-7 1/5/2006 603.62 12.15 591.47 VB-1-7D 1/9/2006 602.80 11.20 591.60 VB-1-8 11/22/2005 603.36 12.15 591.21 VB-1-8 1/5/2006 603.36 11.75 591.61 VB-1-8D 1/9/2006 602.49 10.52 591.97 VB-1-9 11/22/2005 601.86 10.76 591.10 VB-1-9 1/5/2006 601.86 10.37 591.49 VB-1-9D 1/10/2006 601.61 9.84 591.77 VB-1-9D 1/13/2006 601.61 10.91 590.70 VB-2-1 11/15/2005 605.71 14.87 590.84 VB-2-1 1/5/2006 605.71 14.57 591.14 VB-2-2 11/15/2005 600.16 8.80 591.36 VB-2-2 12/5/2005 600.16 8.89 591.27 VB-2-2 1/4/2006 600.16 8.60 591.56 VB-2-2D 12/21/2005 598.95 8.05 590.90 VB-2-2D 12/23/2005 598.95 8.00 590.95 VB-2-2D 1/4/2006 598.95 7.83 591.12 VB-2-3 11/15/2005 600.16 9.03 591.13 VB-2-3 1/5/2006 600.16 9.22 590.94 VB-2-4 11/15/2005 600.82 10.00 590.82 VB-2-4 1/5/2006 600.82 9.95 590.87 VB-2-5 11/15/2005 599.82 9.20 590.62 VB-2-5 1/3/2006 599.82 9.30 590.52 VB-2-5D 12/14/2005 596.78 6.02 590.76 VB-2-5D 1/3/2006 596.78 6.61 590.17 VB-2-6 11/15/2005 601.44 10.80 590.64 VB-2-6 12/5/2005 601.44 10.93 590.51 CRA 016841 (12)

TABLE 4.2 Page 9 of 9

SUMMARY

OF GROUNDWATER ELEVATIONS 1 EXELON GENERATION BRAIDWOOD STATION Top of Casing Depth to Water Groundwater Elevation Monitoring Location Date (ft amsl) 2 (ft btoc) 3 (ft amsl)

VB-2-6 1/3/2006 601.44 7.94 593.50 VB-2-6D 12/14/2005 596.77 6.12 590.65 VB-2-6D 1/3/2006 596.77 6.11 590.66 VB-2-7 12/14/2005 602.04 11.19 590.85 VB-2-7 1/4/2006 602.04 10.99 591.05 VB-2-7D 12/14/2005 602.28 11.39 590.89 VB-2-7D 1/4/2006 602.28 11.26 591.02 VB-2-8 12/14/2005 599.05 8.27 590.78 VB-2-8 1/5/2006 599.05 8.02 591.03 VB-2-9 1/10/2006 599.48 8.49 590.99 VB-2-9 1/12/2006 599.48 8.49 590.99 VB-2-9D 1/10/2006 599.93 9.69 590.24 VB-2-9D 1/12/2006 599.93 9.69 590.24 VB-3-1 11/15/2005 600.99 9.83 591.16 VB-3-1 1/5/2006 600.99 9.75 591.24 VB-3-2 11/15/2005 601.51 10.22 591.29 VB-3-2 1/5/2006 601.51 9.98 591.53 VB-3-3 11/15/2005 600.03 9.05 590.98 VB-3-3 1/5/2006 600.03 8.79 591.24 VB-3-4 11/15/2005 601.37 10.58 590.79 VB-3-4 12/5/2005 601.37 10.43 590.94 VB-3-4 1/3/2006 601.37 10.33 591.04 VB-3-4D 12/14/2005 600.82 9.79 591.03 VB-3-4D 1/3/2006 600.82 9.57 591.25 VB-3-5 11/22/2005 599.24 9.44 589.80 VB-3-5 1/5/2006 599.24 7.94 591.30 VB-3-6 11/22/2005 599.18 8.60 590.58 VB-3-6 1/5/2006 599.18 8.28 590.90 VB-3-7 12/2/2005 599.49 8.19 591.30 VB-3-7 12/14/2005 599.49 5.72 593.77 VB-3-7 1/3/2006 599.49 7.91 591.58 VB-3-7D 12/14/2005 597.04 5.72 591.32 VB-3-7D 1/3/2006 597.04 5.45 591.59 VB-3-8 12/2/2005 599.51 8.20 591.31 VB-3-8 1/5/2006 599.51 7.82 591.69 VB-3-9D 12/13/2005 596.62 6.37 590.25 VB-3-9D 1/4/2006 596.62 5.64 590.98 VB-3-10 12/16/2005 599.28 8.22 591.06 VB-3-10 1/3/2006 599.28 7.88 591.40 VB-3-10D 12/16/2005 598.44 7.28 591.16 VB-3-10D 1/3/2006 598.44 7.07 591.37 1

Water level data through March 1, 2006 2

ft amsl - feet above mean sea level 3

ft btoc - feet below top of casing CRA 016841 (12)

TABLE 4.3 Page 1 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 A-1 1/11/06 9.01 10 7.11 766 11.67

• slightly cloudy peristaltic A-1 1/11/06 12 7.06 802 11.61

• slightly cloudy peristaltic A-1 1/11/06 14 7.01 814 11.48

• clear peristaltic A-1D 1/11/06 9.33 10 6.64 555 10.22

• slightly cloudy peristaltic A-1D 1/11/06 13 7.15 559 10.86

• slightly cloudy peristaltic A-1D 1/11/06 16 7.20 560 10.89

• slightly cloudy peristaltic BL-01 11/17/05 13.43 5 6.59 345 15.74

• cloudy peristaltic BL-01 11/17/05 10 6.62 348 15.61

• slightly cloudy peristaltic BL-01 11/17/05 15 6.64 339 15.60

• slightly cloudy peristaltic BL-02 11/17/05 12.92 5 6.48 425 13.36

• cloudy peristaltic BL-02 11/17/05 10 6.43 421 13.20

• slightly cloudy peristaltic BL-02 11/17/05 15 6.39 416 13.17

• clear peristaltic BL-02 11/17/05 20 6.40 415 13.21

• clear peristaltic BL-03 11/18/05 13.34 5 7.25 280 17.73

• cloudy peristaltic BL-03 11/18/05 10 7.06 296 17.75

• slightly cloudy peristaltic BL-03 11/18/05 15 7.01 294 17.78

• clear peristaltic BL-04 11/18/05 10.93 5 6.70 499 17.42

• clear peristaltic BL-04 11/18/05 10 6.62 524 17.41

• clear peristaltic BL-04 11/18/05 15 6.60 520 17.44

• clear peristaltic BL-05 11/18/05 11.77 5 6.73 694 15.57

• cloudy peristaltic BL-05 11/18/05 10 6.59 697 15.58

• cloudy peristaltic BL-05 11/18/05 15 6.54 687 15.46

• slightly cloudy peristaltic BL-06 11/18/05 11.00 5 6.70 435 15.33

• slightly cloudy peristaltic BL-06 11/18/05 10 6.61 436 15.38

• slightly cloudy peristaltic BL-06 11/18/05 15 6.57 437 15.37

• slightly cloudy peristaltic CRA 016841 (12)

TABLE 4.3 Page 2 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-07 11/18/05 10.28 5 6.97 656 15.75

• slightly cloudy peristaltic BL-07 11/18/05 10 6.77 648 15.77

• clear peristaltic BL-07 11/18/05 15 6.71 643 15.76

• clear peristaltic BL-08 11/18/05 11.40 5 7.40 220 14.91

• slightly cloudy peristaltic BL-08 11/18/05 10 7.32 217 14.92

• slightly cloudy peristaltic BL-08 11/18/05 15 7.28 215 14.92

• slightly cloudy peristaltic BL-09 11/18/05 11.82 1 * * *

• sand filled well screen- DRY

• BL-9 12/23/05 11.31 10 8.50 335 13.90

• slightly cloudy peristaltic BL-9 12/23/05 13 8.50 346 14.20

• slightly cloudy peristaltic BL-9 12/23/05 16 8.50 346 14.20

• clear peristaltic BL-9 1/11/06 11.01 10 8.38 369 14.20

• clear peristaltic BL-9 1/11/06 13 8.40 362 13.90

• clear peristaltic BL-9 1/11/06 16 8.40 361 13.80

• clear peristaltic BL-9 1/18/06

• 10 7.00 467 12.39

• clear peristaltic BL-9 1/18/06 13 7.18 466 12.37

• clear peristaltic BL-9 1/18/06 16 7.31 466 12.30

• clear peristaltic BL-9 2/15/06 10.35 10 7.25 307 13.50

• clear peristaltic BL-9 2/15/06 13 7.26 307 13.60

• clear peristaltic BL-9 2/15/06 16 7.27 307 13.70

• clear peristaltic BL-09 1/25/06

• 10 8.33 359 9.90 51.7 clear peristaltic BL-09 1/25/06 15 8.38 346 10.40 36.2 clear peristaltic BL-09 1/25/06 20 8.37 348 10.50 19.6 clear peristaltic BL-09 2/1/06 10.65 10 7.22 319 14.20

• clear peristaltic BL-09 2/1/06 13 7.24 313 14.50

• clear peristaltic BL-09 2/1/06 16 7.26 312 14.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 3 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-09 2/9/06 10.44 5 6.61 414 12.18

• clear peristaltic BL-09 2/9/06 10 6.51 413 12.21

• clear peristaltic BL-09 2/9/06 15 6.52 413 12.29

• clear peristaltic BL-09 2/22/06 10.23 10 7.34 278 11.90

• clear peristaltic BL-09 2/22/06 13 7.23 186 12.30

• clear peristaltic BL-09 2/22/06 16 7.20 186 12.30

• clear peristaltic BL-09 3/1/06 8.21 10 8.01 192 13.80

• clear peristaltic BL-09 3/1/06 13 8.01 192 13.80

• clear peristaltic BL-09 3/1/06 16 8.01 192 13.80

• clear peristaltic BL-09 3/7/06 10.20 10 8.00 190 13.00

• clear peristaltic BL-09 3/7/06 13 7.99 190 13.10

• clear peristaltic BL-09 3/7/06 16 7.99 190 13.10

• clear peristaltic BL-9D 12/23/05 9.35 10 7.95 560 13.02

• slightly cloudy peristaltic BL-9D 12/23/05 13 7.70 569 13.28

• clear peristaltic BL-9D 12/23/05 16 7.57 569 13.32

• clear peristaltic BL-9D 1/11/06 9.08 10 8.05 515 13.90

• clear peristaltic BL-9D 1/11/06 13 7.97 519 13.90

• clear peristaltic BL-9D 1/11/06 16 7.95 519 13.90

• clear peristaltic BL-9D 1/18/06

• 10 6.76 651 12.51

• clear peristaltic BL-9D 1/18/06 12 6.70 640 12.09

• clear peristaltic BL-9D 1/18/06 14 6.72 641 12.09

• clear peristaltic BL-9D 2/15/06 8.37 10 7.18 443 14.10

• clear peristaltic BL-9D 2/15/06 13 7.18 444 14.30

• clear peristaltic BL-9D 2/15/06 16 7.18 444 14.30

• clear peristaltic BL-09D 1/25/06

• 10 8.30 485 10.20 51 clear peristaltic BL-09D 1/25/06 15 8.28 491 10.70 32.8 clear peristaltic BL-09D 1/25/06 20 8.27 499 11.20 26.7 clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 4 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-09D 2/1/06 8.68 10 7.07 450 14.90

• clear peristaltic BL-09D 2/1/06 13 7.11 451 15.00

• clear peristaltic BL-09D 2/1/06 16 7.13 450 15.10

• clear peristaltic BL-09D 2/9/06 8.48 5 6.22 632 13.06

• clear peristaltic BL-09D 2/9/06 10 6.18 635 13.17

• clear peristaltic BL-09D 2/9/06 15 6.18 636 13.20

• clear peristaltic BL-09D 2/22/06 8.27 12 6.95 377 12.60

• clear peristaltic BL-09D 2/22/06 15 6.88 377 12.60

• clear peristaltic BL-09D 2/22/06 18 6.86 379 12.70

• clear peristaltic BL-09D 3/1/06 8.21 10 7.81 478 14.20

• clear peristaltic BL-09D 3/1/06 13 7.78 478 14.20

• clear peristaltic BL-09D 3/1/06 16 7.75 478 14.20

• clear peristaltic BL-09D 3/7/06 8.25 12 7.72 464 13.40

• clear peristaltic BL-09D 3/7/06 15 7.68 466 13.50

• clear peristaltic BL-09D 3/7/06 18 7.61 466 13.50

• clear peristaltic BL-10 11/17/05 14.29 5 7.21 210 15.74

• slightly cloudy peristaltic BL-10 11/17/05 10 7.20 208 15.70

• clear peristaltic BL-10 11/17/05 15 7.22 207 15.66

• clear peristaltic BL-10 1/4/06 14.03 10 7.11 414 12.19

• clear peristaltic BL-10 1/4/06 13 7.32 236 13.55

• clear peristaltic BL-10 1/4/06 16 7.39 235 13.50

• clear peristaltic BL-10D 1/4/06 13.81 10 7.01 670 13.94

• slightly cloudy peristaltic BL-10D 1/4/06 13 7.04 668 14.00

• clear peristaltic BL-10D 1/4/06 16 7.06 669 14.03

• clear peristaltic BL-11 11/17/05 9.70 5 6.80 425 16.64

• slightly cloudy peristaltic BL-11 11/17/05 10 6.66 423 16.75

• clear peristaltic BL-11 11/17/05 15 6.61 422 16.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 5 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-11 1/3/06 9.41 5 7.21 371 13.80 36.9 clear peristaltic BL-11 1/3/06 8 7.21 373 14.10 28.2 clear peristaltic BL-11 1/3/06 11 7.19 375 14.30 19.9 clear peristaltic BL-11D 12/15/05 7.82 30 7.60 414 14.70

• clear peristaltic BL-11D 12/15/05 33 7.50 411 14.80

• clear peristaltic BL-11D 12/15/05 36 7.39 412 14.39

• clear peristaltic BL-11D 1/3/06 7.56 5 7.18 364 14.70 56.8 cloudy peristaltic BL-11D 1/3/06 8 7.17 366 14.60 47.9 cloudy peristaltic BL-11D 1/3/06 11 7.17 361 14.70 36.2 clear peristaltic BL-12 11/17/05 10.41 5 6.89 360 16.73

• cloudy peristaltic BL-12 11/17/05 10 6.78 357 16.74

• slightly cloudy peristaltic BL-12 11/17/05 15 6.73 355 16.72

• clear peristaltic BL-12 1/3/06 10.05 10 6.81 335 14.23

• slightly cloudy peristaltic BL-12 1/3/06 13 6.83 329 14.22

• slightly cloudy peristaltic BL-12 1/3/06 16 6.82 315 14.25

• clear peristaltic BL-12D 12/15/05 8.54 24 7.35 418 14.89

• clear peristaltic BL-12D 12/15/05 27 7.35 419 14.73

• clear peristaltic BL-12D 12/15/05 30 7.34 418 14.85

• clear peristaltic BL-12D 1/3/06 8.40 10 6.88 429 14.65

• clear peristaltic BL-12D 1/3/06 13 6.82 427 14.68

• clear peristaltic BL-12D 1/3/06 16 6.77 418 14.70

• clear peristaltic BL-13 11/17/05 10.27 5 6.87 515 18.12

• cloudy peristaltic BL-13 11/17/05 10 6.68 505 17.95

• slightly cloudy peristaltic BL-13 11/17/05 15 6.62 502 18.08

• slightly cloudy peristaltic BL-13 1/3/06 9.94 10 7.24 423 13.10 32.7 clear peristaltic BL-13 1/3/06 13 7.21 415 13.60 24.2 clear peristaltic BL-13 1/3/06 16 7.19 415 13.90 17.8 clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 6 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 Bl-13D 12/15/05 9.39 42 7.07 470 15.28

• clear peristaltic Bl-13D 12/15/05 45 7.10 471 15.24

• clear peristaltic Bl-13D 12/15/05 48 7.12 472 15.18

• clear peristaltic BL-13D 1/3/06 9.17 5 7.17 399 14.80 47.1 cloudy peristaltic BL-13D 1/3/06 8 7.16 400 14.70 34.3 clear peristaltic BL-13D 1/3/06 11 7.15 403 14.50 26.7 clear peristaltic BL-14 11/17/05 9.91 5 7.01 235 17.53

• cloudy peristaltic BL-14 11/17/05 10 6.97 231 17.62

• cloudy peristaltic BL-14 11/17/05 15 6.94 289 17.42

• cloudy peristaltic BL-14 11/17/05 20 6.93 287 17.44

• slightly cloudy peristaltic BL-14 1/3/06 9.65 10 6.93 301 14.58

• clear peristaltic BL-14 1/3/06 13 6.99 302 14.62

• clear peristaltic BL-14 1/3/06 16 6.99 303 14.62

• clear peristaltic BL-14D 12/15/05 28.71 45 7.07 463 14.77

• clear peristaltic BL-14D 12/15/05 48 7.07 464 14.77

• clear peristaltic BL-14D 12/15/05 51 7.08 465 14.86

• clear peristaltic BL-14D 1/3/06 8.26 10 6.53 519 15.04

• slightly cloudy peristaltic BL-14D 1/3/06 13 6.63 520 15.21

• slightly cloudy peristaltic BL-14D 1/3/06 16 6.61 520 15.35

• clear peristaltic BL-15 11/17/05 9.98 5 7.08 350 17.20

• slightly cloudy peristaltic BL-15 11/17/05 10 6.99 347 17.37

• clear peristaltic BL-15 11/17/05 15 6.95 354 17.25

• clear peristaltic BL-15 1/3/06 9.57 10 7.26 271 13.50 33.6 clear peristaltic BL-15 1/3/06 13 7.26 262 14.10 22.6 clear peristaltic BL-15 1/3/06 16 7.26 265 14.20 16.8 clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 7 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-15D 12/16/05 6.20 10 8.20 309 14.60

• clear peristaltic BL-15D 12/16/05 13 8.15 310 15.20

• clear peristaltic BL-15D 12/16/05 16 8.12 312 15.20

• clear peristaltic BL-15D 1/3/06 6.92 5 7.24 299 14.70 18.2 clear peristaltic BL-15D 1/3/06 8 7.23 316 14.80 15.6 clear peristaltic BL-15D 1/3/06 11 7.22 302 15.20 11.4 clear peristaltic BL-16 11/17/05 9.40 5 6.57 580 17.47

• slightly cloudy peristaltic BL-16 11/17/05 10 6.45 571 17.50

• clear peristaltic BL-16 11/17/05 15 6.47 570 17.46

• clear peristaltic BL-16 1/3/06 9.05 10 6.70 655 13.28

• clear peristaltic BL-16 1/3/06 13 6.64 653 13.33

• clear peristaltic BL-16 1/3/06 16 6.61 652 13.35

• clear peristaltic BL-16D 12/16/05 7.60 10 8.39 256 13.00

• clear peristaltic BL-16D 12/16/05 13 8.35 251 14.20

• clear peristaltic BL-16D 12/16/05 16 8.33 250 14.70

• clear peristaltic BL-16D 1/3/06 6.92 10 6.75 301 14.53

• slightly cloudy peristaltic BL-16D 1/3/06 13 6.91 301 14.63

• clear peristaltic BL-16D 1/3/06 16 6.93 303 14.62

• clear peristaltic BL-17 12/1/05 6.47 10 7.43 412 14.30

• slightly cloudy, gray peristaltic BL-17 12/1/05 15 7.37 409 14.80

• slightly cloudy, gray peristaltic BL-17 12/1/05 20 7.32 407 15.20

• slightly cloudy, gray peristaltic BL-17 12/5/05 6.50 5 7.28 355 14.40 *

• peristaltic BL-17 12/5/05 10 7.23 350 14.20 *

• peristaltic BL-17 12/5/05 15 7.26 360 14.20 *

• peristaltic BL-17 1/3/06 6.37 10 7.65 275 14.00

• clear peristaltic BL-17 1/3/06 15 7.61 275 14.20

• clear peristaltic BL-17 1/3/06 20 7.61 274 14.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 8 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 BL-17D 12/12/05 7.21 10 8.37 222 14.60

• cloudy peristaltic BL-17D 12/12/05 13 8.29 215 15.10

• cloudy peristaltic BL-17D 1/3/06 6.80 10 8.11 209 14.60

• clear peristaltic BL-17D 1/3/06 15 8.15 207 14.70

• clear peristaltic BL-17D 1/3/06 20 8.16 207 14.80

• clear peristaltic BL-18 12/1/05 6.71 10 6.94 529 14.10

• cloudy, gray peristaltic BL-18 12/1/05 15 7.28 519 14.70

• cloudy, gray peristaltic BL-18 12/1/05 20 7.40 521 14.70

• slightly cloudy, gray peristaltic BL-18D 2/7/06 7.07 10 7.52 244 17.40

• cloudy peristaltic BL-18D 2/7/06 13 7.42 179 18.40

• slightly cloudy peristaltic BL-18D 2/7/06 16 7.39 177 18.40

• clear peristaltic BL-19 12/1/05 5.04 10 7.44 565 12.30

• cloudy, gray peristaltic BL-19 12/1/05 15 7.37 556 12.20

• slightly cloudy, gray peristaltic BL-19 12/1/05 20 7.36 555 12.00

• slightly cloudy, gray peristaltic BL-19D 2/7/06 4.90 10 7.50 270 14.60

• cloudy peristaltic BL-19D 2/7/06 13 7.39 261 14.50

• slightly cloudy peristaltic BL-19D 2/7/06 16 7.35 256 15.10

• slightly cloudy peristaltic BL-20D 12/23/05 9.56 10 7.54 411 14.33

• clear peristaltic BL-20D 12/23/05 12 7.50 398 14.48

• clear peristaltic BL-20D 12/23/05 14 7.45 390 14.50

• clear peristaltic BL-20D 1/4/06 9.16 10 7.36 320 13.10 28.1 clear peristaltic BL-20D 1/4/06 13 7.31 296 13.60 21.7 clear peristaltic BL-20D 1/4/06 16 7.26 310 13.90 17.2 clear peristaltic C-1 12/12/05 7.21 10 7.46 584 13.60

• slightly cloudy peristaltic C-1 12/12/05 13 7.45 584 13.40

• clear peristaltic C-1 12/12/05 16 7.41 585 13.53

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 9 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 C-1D 12/12/05 7.35 10 7.83 551 13.30

• cloudy peristaltic C-1D 12/12/05 13 7.81 556 13.20

• cloudy peristaltic C-1D 12/12/05 16 7.73 563 12.50

• cloudy peristaltic C-1D 1/3/06 6.79 5 7.70 584 13.10

• clear peristaltic C-1D 1/3/06 10 7.71 578 13.10

• clear peristaltic C-1D 1/3/06 15 7.73 578 13.10

• clear peristaltic C-2 1/24/06 9.00 7 6.31 456 10.87

• clear peristaltic C-2 1/24/06 10 6.31 450 10.93

• clear peristaltic C-2 1/24/06 13 5.97 449 10.93

• clear peristaltic C-2 2/1/06 8.50 10 6.73 305 12.80

• clear peristaltic C-2 2/1/06 13 6.58 302 12.80

• clear peristaltic C-2 2/1/06 16 6.49 306 12.80

• clear peristaltic C-2 2/9/06 8.56 5 5.48 392 10.11

• slightly cloudy peristaltic C-2 2/9/06 10 5.42 394 10.05

• slightly cloudy peristaltic C-2 2/9/06 15 5.37 395 9.95

• clear peristaltic C-2 2/15/06 8.70 10 6.55 294 11.50

• clear peristaltic C-2 2/15/06 12 6.53 294 11.60

• clear peristaltic C-2 2/15/06 14 6.52 294 11.60

• clear peristaltic C-2 2/22/06 8.63 12 5.96 193 11.00

• clear peristaltic C-2 2/22/06 15 5.95 194 10.90

• clear peristaltic C-2 2/22/06 18 5.93 196 10.90

• clear peristaltic C-2 3/2/06

• 10 6.86 191 11.10

• clear peristaltic C-2 3/2/06 13 6.80 192 11.10

• clear peristaltic C-2 3/2/06 16 6.77 193 11.10

• clear peristaltic C-2 3/7/06 8.60 5 6.64 420 9.70 *

• peristaltic C-2 3/7/06 10 6.29 417 9.47 *

• peristaltic C-2 3/7/06 15 6.25 417 9.53 *

• peristaltic CRA 016841 (12)

TABLE 4.3 Page 10 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 C-2D 1/24/06 7.09 10 6.84 657 12.13

• clear peristaltic C-2D 1/24/06 13 6.76 665 12.13

• clear peristaltic C-2D 1/24/06 16 6.70 664 12.10

• clear peristaltic C-2D 2/1/06 6.75 10 7.15 443 13.30

• slightly cloudy peristaltic C-2D 2/1/06 13 7.11 442 13.30

• slightly cloudy peristaltic C-2D 2/1/06 16 7.10 441 13.50

• clear peristaltic C-2D 2/9/06 6.76 5 6.26 621 10.80

• very cloudy peristaltic C-2D 2/9/06 10 6.08 618 11.11

• slightly cloudy peristaltic C-2D 2/9/06 15 6.03 620 10.88

• clear peristaltic C-2D 2/15/06 6.90 10 7.14 432 12.70

• clear peristaltic C-2D 2/15/06 13 7.11 436 12.70

• clear peristaltic C-2D 2/15/06 16 7.11 436 12.70

• clear peristaltic C-2D 2/22/06 6.85 10 6.64 372 11.60

• clear peristaltic C-2D 2/22/06 13 6.56 371 11.80

• clear peristaltic C-2D 2/22/06 16 6.54 370 11.90

• clear peristaltic C-2D 3/2/06

• 10 7.22 185 12.20

• clear peristaltic C-2D 3/2/06 13 7.01 185 12.20

• clear peristaltic C-2D 3/2/06 16 7.00 185 12.20

• clear peristaltic C-2D 3/7/06 6.82 10 6.53 654 10.42 *

• peristaltic C-2D 3/7/06 15 6.81 664 10.71 *

• peristaltic C-2D 3/7/06 20 6.82 665 10.76 *

• peristaltic C-2D 3/7/06 25 6.84 665 10.80 *

• peristaltic D-1 12/6/05 12.10 10 6.96 480 13.10 *

• peristaltic D-1 12/6/05 15 6.95 486 13.10 *

• peristaltic D-1 12/6/05 20 6.95 482 12.90 *

• peristaltic CRA 016841 (12)

TABLE 4.3 Page 11 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 D-1 1/4/06 11.90 10 7.71 513 12.00 104

• peristaltic D-1 1/4/06 15 7.63 512 12.00 19.7

• peristaltic D-1 1/4/06 20 7.61 512 12.00 *

• peristaltic D1-1D 1/4/06 12.00 10 6.83 1053 11.45

• clear peristaltic D1-1D 1/4/06 12 6.81 1057 11.55

• clear peristaltic D1-1D 1/4/06 14 6.75 1058 11.64

• clear peristaltic D-1D 12/23/05 12.04 10 7.70 770 13.20

• slightly cloudy peristaltic D-1D 12/23/05 13 7.65 776 13.10

• slightly cloudy peristaltic D-1D 12/23/05 16 7.64 780 13.00

• clear peristaltic D-1D 12/23/05 D-2 12/5/05 10.52 10 6.95 764 10.20 *

• peristaltic D-2 12/5/05 15 7.13 460 10.10 *

• peristaltic D-2 12/5/05 17 7.28 684 10.20 *

• peristaltic D-2 1/4/06 10.31 7 6.35 935 9.90

• clear peristaltic D-2 1/4/06 9 6.33 932 9.94

• clear peristaltic D-2 1/4/06 11 6.31 932 9.96

• clear peristaltic D-2D 1/4/06 9.76 10 6.87 1414 12.17

• clear peristaltic D-2D 1/4/06 13 6.71 1412 12.21

• clear peristaltic D-2D 1/4/06 16 6.62 1413 12.24

• clear peristaltic D-3 12/2/05 11.05 10 7.58 653 13.10

• cloudy peristaltic D-3 12/2/05 15 7.36 656 14.00

• slightly cloudy peristaltic D-3 12/2/05 20 7.36 659 14.10

• slightly cloudy peristaltic D-3 1/4/06 10.85 10 6.49 329 11.75

• slightly cloudy peristaltic D-3 1/4/06 13 6.38 399 11.70

• slightly cloudy peristaltic D-3 1/4/06 16 6.39 386 11.74

• clear peristaltic D-3D 12/23/05 10.71 10 7.22 756 13.16

• slightly cloudy peristaltic D-3D 12/23/05 12 7.13 772 13.23

• clear peristaltic D-3D 12/23/05 14 7.11 778 13.14

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 12 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 D-3D 1/4/06 10.60 10 6.73 728 12.62

• slightly cloudy peristaltic D-3D 1/4/06 13 6.69 802 12.68

• clear peristaltic D-3D 1/4/06 16 6.69 812 12.69

• clear peristaltic D-5 12/2/05 10.86 10 7.81 635 12.00

• cloudy peristaltic D-5 12/2/05 15 7.60 651 12.20

• cloudy peristaltic D-5 12/2/05 20 7.57 652 12.30

• cloudy peristaltic F-1 12/12/05 7.40 10 7.33 766 14.40

• cloudy peristaltic F-1 12/12/05 13 7.29 759 14.50

• slightly cloudy peristaltic F-1 12/12/05 16 7.30 763 14.30

• slightly cloudy peristaltic F-1 1/3/06 7.19 10 7.05 839 12.92

• slightly cloudy peristaltic F-1 1/3/06 13 7.28 837 12.98

• slightly cloudy peristaltic F-1 1/3/06 16 7.32 826 12.97

• clear peristaltic F-1D 12/12/05 7.35 10 8.07 594 14.80

• slightly cloudy peristaltic F-1D 12/12/05 13 7.80 592 14.50

• slightly cloudy peristaltic F-1D 12/12/05 16 7.59 589 14.30

• clear peristaltic F-1D 1/3/06 7.10 10 7.95 652 13.57

• slightly cloudy peristaltic F-1D 1/3/06 13 7.92 652 13.59

• clear peristaltic F-1D 1/3/06 16 7.87 651 13.60

• clear peristaltic F-2D 1/9/06 7.26 10 7.01 501 12.77

• clear peristaltic F-2D 1/9/06 13 6.98 501 12.70

• clear peristaltic F-2D 1/9/06 16 6.93 500 12.54

• clear peristaltic F-3D 1/9/06 8.57 10 7.57 357 14.65

• slightly cloudy peristaltic F-3D 1/9/06 12 7.60 347 14.22

• clear peristaltic F-3D 1/9/06 14 7.61 346 14.14

• clear peristaltic F-3D 1/12/06 8.67 10 7.42 289 12.80

• clear peristaltic F-3D 1/12/06 12 7.38 275 12.77

• clear peristaltic F-3D 1/12/06 14 7.35 278 12.85

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 13 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 F-4D 1/24/06 10.87 15 6.77 567 11.09

• cloudy peristaltic F-4D 1/24/06 18 6.70 569 10.91

• slightly cloudy peristaltic F-4D 1/24/06 21 6.71 570 10.98

• slightly cloudy peristaltic F-5D 1/24/06 6.65 10 7.41 619 12.00

• clear peristaltic F-5D 1/24/06 13 7.09 637 12.27

• clear peristaltic F-5D 1/24/06 16 6.95 626 12.26

• clear peristaltic F-6D 1/24/06 9.26 10 6.41 592 13.51

• cloudy peristaltic F-6D 1/24/06 13 6.86 589 13.68

• cloudy peristaltic F-6D 1/24/06 16 6.82 587 13.49

• slightly cloudy peristaltic F-7D 1/24/06 8.48 10 6.89 761 12.39

• clear peristaltic F-7D 1/24/06 12 6.88 813 12.21

• clear peristaltic F-7D 1/24/06 14 6.82 856 12.21

• clear peristaltic F-8D 1/24/06 9.70 10 7.14 557 13.12

• slightly cloudy peristaltic F-8D 1/24/06 13 6.48 554 13.03

• clear peristaltic F-8D 1/24/06 16 6.95 556 12.99

• clear peristaltic G-1 12/6/05 5.55 10 7.71 614 13.00

• cloudy peristaltic G-1 12/6/05 15 7.51 618 13.40

• slightly cloudy peristaltic G-1 12/6/05 20 7.36 624 12.80

• slightly cloudy peristaltic G-2 12/6/05 5.31 10 7.78 487 12.60

• slightly cloudy peristaltic G-2 12/6/05 15 7.78 481 13.10

• slightly cloudy peristaltic G-2 12/6/05 20 7.63 491 12.30

• slightly cloudy peristaltic G-2D 1/26/06 3.65 10 7.89 493 11.70 *

• peristaltic G-2D 1/26/06 15 7.86 502 10.90 *

• peristaltic G-2D 1/26/06 20 7.83 511 11.10 *

• peristaltic G-3 12/6/05 7.25 10 7.56 525 14.30

• slightly cloudy peristaltic G-3 12/6/05 15 7.63 495 13.90

• clear peristaltic G-3 12/6/05 20 7.35 490 13.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 14 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 MW-101 11/15/05 11.60 5 6.96 151 13.70 38.8 clear with suspended particles peristaltic MW-101 11/15/05 6 DRY MW-103 11/15/05 7.70 5 7.17 340 12.20 100 cloudy with suspended particles peristaltic MW-103 11/15/05 15 7.23 341 12.20 64.3 slightly cloudy with suspended particles peristaltic MW-103 11/15/05 20 7.19 340 12.60 21.2 clear with suspended particles peristaltic MW-103 11/15/05 25 7.22 341 12.20 13.1 clear peristaltic MW-105 11/15/05 9.30 5 7.06 554 15.30 117 cloudy peristaltic MW-105 11/15/05 10 7.15 475 15.50 63.2 slightly cloudy peristaltic MW-105 11/15/05 15 7.17 464 15.50 36.4 clear with suspended particles peristaltic MW-105 11/15/05 20 7.17 457 15.50 20.5 clear peristaltic MW-105 1/4/06 6.05 10 7.34 354 12.60 18.1 clear peristaltic MW-105 1/4/06 13 7.27 357 12.80 11.3 clear peristaltic MW-105 1/4/06 16 7.24 360 12.80 8.4 clear peristaltic MW-105D 12/16/05 6.81 10 8.18 378 14.20

• clear peristaltic MW-105D 12/16/05 13 8.02 382 14.50

• clear peristaltic MW-105D 12/16/05 16 7.92 382 14.30

• clear peristaltic MW-105D 1/4/06 6.48 10 7.17 366 13.80 22.6 clear peristaltic MW-105D 1/4/06 13 7.14 368 14.20 17.5 clear peristaltic MW-105D 1/4/06 16 7.14 368 14.30 15.2 clear peristaltic MW-106 11/14/05 10.82 10 8.14 323 13.70 7.17 clear peristaltic MW-106 11/14/05 15 7.87 316 14.60 7.74 clear peristaltic MW-106 11/14/05 20 7.73 318 14.70 8.95 clear peristaltic MW-106 11/14/05 25 7.73 323 14.60 5.17 clear peristaltic MW-106 1/4/06 10.42 10 7.27 317 10.40 16.7 clear peristaltic MW-106 1/4/06 13 7.27 309 10.30 12.2 clear peristaltic MW-106 1/4/06 16 7.25 309 10.40 9.8 clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 15 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 MW-106D 12/16/05 9.84 10 7.94 467 12.20

• clear peristaltic MW-106D 12/16/05 13 7.81 471 12.60

• clear peristaltic MW-106D 12/16/05 16 7.76 473 12.90

• clear peristaltic MW-106D 1/4/06 9.52 10 7.18 435 11.30 20.1 clear peristaltic MW-106D 1/4/06 13 7.14 438 11.60 16.8 clear peristaltic MW-106D 1/4/06 16 7.13 442 11.70 12.5 clear peristaltic MW-107 11/16/05 10.71 5.00 7.41 415 14.00 29.8 clear with suspended particles peristaltic MW-107 11/16/05 10.00 7.46 405 14.80 12.6 clear peristaltic MW-107 11/16/05 15.00 7.48 402 14.30 8.73 clear peristaltic MW-107 11/16/05 20.00 7.50 401 14.20 5.75 clear peristaltic MW-108 11/16/05 11.18 5.00 6.98 782 14.30 2.74 clear peristaltic MW-108 11/16/05 10.00 7.02 773 13.80 2.52 clear peristaltic MW-108 11/16/05 15.00 7.03 773 13.70 3.16 clear peristaltic MW-110 11/14/05 19.28 10 7.14 950 13.60 11 clear peristaltic MW-110 11/14/05 20 7.24 878 13.60 5.03 clear peristaltic MW-110 11/14/05 25 7.31 866 13.30 3.6 clear peristaltic MW-110 11/14/05 19.26 30 7.33 860 13.80 3.18 clear peristaltic MW-110 11/16/05 19.19 5.00 7.06 1024 13.20 6.05 clear peristaltic MW-110 11/16/05 10.00 7.09 1011 12.50 3.24 clear peristaltic MW-110 11/16/05 15.00 7.09 1008 12.50 2.53 clear peristaltic MW-110 11/16/05 20.00 7.12 1002 12.60 2.42 clear peristaltic MW-110 1/4/06 19.46 5 7.08 1105 11.27

• clear peristaltic MW-110 1/4/06 10 7.07 1105 11.23

• clear peristaltic MW-110 1/4/06 15 7.06 1105 11.22

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 16 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 MW-111 11/15/05 16.74 5 7.12 300 13.90 5.89 clear peristaltic MW-111 11/15/05 10 7.59 181 13.80 2.96 clear peristaltic MW-111 11/15/05 15 7.64 160 13.80 1.87 clear peristaltic MW-111 11/15/05 20 7.66 159 13.80 1.55 clear peristaltic MW-111 11/15/05 MW-111 1/4/06 16.55 10 7.30 118 11.80 11.3 clear peristaltic MW-111 1/4/06 13 7.33 116 12.20 9.5 clear peristaltic MW-111 1/4/06 16 7.33 116 12.20 7.8 clear peristaltic MW-111 1/4/06 MW-111D 1/9/06 14.35 10 7.69 345 15.36

• slightly cloudy peristaltic MW-111D 1/9/06 13 7.85 346 14.90

• slightly cloudy peristaltic MW-111D 1/9/06 16 7.88 345 14.83

• clear peristaltic MW-111D 1/9/06 MW-112 11/15/05 12.13 5 7.11 402 15.00 65.3 slightly cloudy peristaltic MW-112 11/15/05 10 7.15 386 15.10 28.7 clear peristaltic MW-112 11/15/05 15 7.16 384 15.10 20.5 clear peristaltic MW-112 11/15/05 MW-112 1/4/06 11.77 5 7.26 335 10.80 18.7 clear peristaltic MW-112 1/4/06 8 7.23 339 10.90 16.4 clear peristaltic MW-112 1/4/06 11 7.20 340 11.20 13.8 clear peristaltic MW-112 1/4/06 MW-112D 1/9/06 9.87 15 7.19 678 14.97

• cloudy peristaltic MW-112D 1/9/06 18 7.12 683 14.66

• slightly cloudy peristaltic MW-112D 1/9/06 21 7.06 686 14.41

• slightly cloudy peristaltic MW-112D 1/9/06 MW-113 11/15/05 8.75 5 6.95 615 12.60 17.5 clear peristaltic MW-113 11/15/05 10 6.96 586 12.60 10.4 clear peristaltic MW-113 11/15/05 15 6.95 568 12.80 7.53 clear peristaltic MW-113 11/15/05 20 6.95 571 12.80 4.76 clear peristaltic MW-113 11/15/05 CRA 016841 (12)

TABLE 4.3 Page 17 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 MW-113 12/5/05 8.89 5 7.14 484 11.70 *

• peristaltic MW-113 12/5/05 10 7.13 477 11.70 *

• peristaltic MW-113 12/5/05 15 7.13 483 11.50 *

• peristaltic MW-113 12/5/05 MW-113 1/3/06 8.97 15 7.52 556 10.90 35.2 clear peristaltic MW-113 1/3/06 18 7.48 509 11.20 24.1 clear peristaltic MW-113 1/3/06 21 7.45 509 11.50 19.2 clear peristaltic MW-113 1/3/06 24 7.44 505 11.40 17.8 clear peristaltic MW-113 1/3/06 MW-113D 12/14/05 6.12 10 7.90 432 12.70

• clear peristaltic MW-113D 12/14/05 13 7.90 431 12.10

• clear peristaltic MW-113D 12/14/05 16 7.77 429 12.20

• clear peristaltic MW-113D 12/14/05 MW-113D 1/3/06 6.13 10 7.40 422 12.20 51.7 cloudy peristaltic MW-113D 1/3/06 13 7.39 418 12.40 39.3 clear peristaltic MW-113D 1/3/06 16 7.38 418 12.40 26.7 clear peristaltic P-1 12/1/05 5.08 10 7.21 432 15.70

• cloudy, gray peristaltic P-1 12/1/05 15 7.46 427 16.40

• cloudy, gray peristaltic P-1 12/1/05 20 7.54 424 16.70

• cloudy, gray peristaltic P-1 12/1/05 P-2 12/2/05 5.95 15 8.47 478 15.60

• cloudy peristaltic P-2 12/2/05 20 8.56 363 17.50

• slightly cloudy peristaltic P-2 12/2/05 25 8.55 352 18.00

• slightly cloudy peristaltic P-2 1/3/06 5.81 10 8.41 391 15.65

• slightly cloudy peristaltic P-2 1/3/06 13 8.63 393 15.67

• slightly cloudy peristaltic P-2 1/3/06 16 8.75 395 15.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 18 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-2D 12/12/05 6.26 10 8.02 369 17.80

• slightly cloudy peristaltic P-2D 12/12/05 13 7.93 364 17.90

• clear peristaltic P-2D 12/12/05 16 7.89 381 16.90

• clear peristaltic P-2D 1/3/06 6.08 10 8.23 412 17.73

• slightly cloudy peristaltic P-2D 1/3/06 13 8.15 412 17.76

• clear peristaltic P-2D 1/3/06 16 8.07 412 17.78

• clear peristaltic P-3 12/2/05 6.08 10 7.25 742 16.40

• cloudy, dark peristaltic P-3 12/2/05 15 7.24 760 17.80

• cloudy peristaltic P-3 12/2/05 20 7.17 762 17.70

• cloudy peristaltic P-4 12/1/05 6.41 10 6.55 923 14.20

• slightly cloudy, gray peristaltic P-4 12/1/05 15 6.50 931 14.80

• slightly cloudy, gray peristaltic P-4 12/1/05 20 6.50 922 15.00

• clear peristaltic P-4 12/6/05 6.50 10 5.78 665 12.00 *

• peristaltic P-4 12/6/05 15 5.95 714 13.80 *

• peristaltic P-4 12/6/05 20 5.97 716 13.60 *

• peristaltic P-4 1/3/06 6.41 10 7.22 727 11.90

• clear peristaltic P-4 1/3/06 15 7.07 723 12.30

• clear peristaltic P-4 1/3/06 20 6.94 754 12.60

• clear peristaltic P-4 1/3/06 25 6.89 761 12.70

• clear peristaltic P-4 1/3/06 30 6.88 761 12.70

• clear peristaltic P-4 1/11/06 6.31 10 7.16 760 12.40

• clear peristaltic P-4 1/11/06 13 7.04 762 12.30

• clear peristaltic P-4 1/11/06 16 7.00 763 12.20

• clear peristaltic P-4 1/18/06 6.28 10 5.83 1043 10.29

• clear peristaltic P-4 1/18/06 13 5.75 1044 10.31

• clear peristaltic P-4 1/18/06 16 5.69 1047 10.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 19 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-4 1/25/06 6.21 10 7.37 753 9.20 195 slightly cloudy peristaltic P-4 1/25/06 15 7.04 775 9.30 122 clear peristaltic P-4 1/25/06 20 7.06 769 10.00 78.3 clear peristaltic P-4 1/25/06 25 7.00 772 9.80 56.4 clear peristaltic P-4 2/1/06 5.95 10 6.99 674 12.20

• clear peristaltic P-4 2/1/06 13 6.66 682 12.40

• clear peristaltic P-4 2/1/06 16 6.46 683 12.40

• clear peristaltic P-4 2/9/06 5.98 5 5.49 1131 10.11

• clear with yellow tint peristaltic P-4 2/9/06 10 5.43 1130 10.15

• clear with yellow tint peristaltic P-4 2/9/06 15 5.38 1132 10.16

• clear with yellow tint peristaltic P-4 2/15/06 6.00 10 7.14 748 11.20

• clear, yellow tint peristaltic P-4 2/15/06 13 6.90 747 11.40

• clear, yellow tint peristaltic P-4 2/15/06 16 6.75 752 11.40

• clear, yellow tint peristaltic P-4 2/22/06 6.06 10 7.24 1043 9.50

• clear peristaltic P-4 2/22/06 13 6.88 1064 10.00

• clear peristaltic P-4 2/22/06 16 6.80 1068 1.00

• clear peristaltic P-4 2/22/06 19 6.72 1079 10.10

• clear peristaltic P-4 3/1/06 5.95 10 7.57 793 11.40

• clear, yellow tint peristaltic P-4 3/1/06 13 7.49 802 10.60

• clear, yellow tint peristaltic P-4 3/1/06 16 7.45 796 10.80

• clear, yellow tint peristaltic P-4 3/7/06 6.00 10 7.22 762 10.50

• clear, yellow tint peristaltic P-4 3/7/06 13 6.86 760 10.70

• clear, yellow tint peristaltic P-4 3/7/06 16 6.83 760 10.70

• clear, yellow tint peristaltic P-4D 12/23/05 8.68 10 7.93 671 12.80

• cloudy peristaltic P-4D 12/23/05 13 7.86 673 13.20

• slightly cloudy peristaltic P-4D 12/23/05 16 7.82 681 13.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 20 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-4D 1/3/06 8.63 12 7.70 691 13.00

• slightly cloudy peristaltic P-4D 1/3/06 17 7.69 691 13.00

• slightly cloudy peristaltic P-4D 1/3/06 22 7.69 688 13.00

• clear peristaltic P-4D 1/11/06 8.55 10 7.67 672 12.90

• slightly cloudy peristaltic P-4D 1/11/06 13 7.71 672 12.70

• slightly cloudy peristaltic P-4D 1/11/06 16 7.72 670 12.70

• clear peristaltic P-4D 1/18/06 8.50 10 6.48 947 11.40

• clear peristaltic P-4D 1/18/06 13 6.48 945 11.57

• clear peristaltic P-4D 1/18/06 16 6.48 943 11.60

• clear peristaltic P-4D 1/25/06 8.48 10 7.94 336 9.90

• cloudy peristaltic P-4D 1/25/06 15 7.86 264 10.10

• slightly cloudy peristaltic P-4D 1/25/06 20 7.84 208 10.00

• slightly cloudy peristaltic P-4D 2/1/06 8.06 10 7.28 551 13.30

• clear peristaltic P-4D 2/1/06 13 7.20 539 13.70

• clear peristaltic P-4D 2/1/06 16 7.16 536 13.80

• clear peristaltic P-4D 2/9/06 8.20 5 6.45 789 11.60

• cloudy peristaltic P-4D 2/9/06 10 6.27 789 11.81

• slightly cloudy peristaltic P-4D 2/9/06 15 6.24 788 11.68

• clear peristaltic P-4D 2/15/06 8.28 10 7.31 562 11.90

• clear peristaltic P-4D 2/15/06 13 7.26 561 12.20

• clear peristaltic P-4D 2/15/06 16 7.22 564 12.30

• clear peristaltic P-4D 2/22/06 8.16 10 6.85 821 11.30

• cloudy peristaltic P-4D 2/22/06 13 7.25 794 11.90

• cloudy peristaltic P-4D 2/22/06 16 7.29 782 11.80

• cloudy peristaltic P-4D 2/22/06 19 7.30 784 12.10

• cloudy peristaltic CRA 016841 (12)

TABLE 4.3 Page 21 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-4D 3/1/06 8.19 12 7.98 648 12.90

• clear peristaltic P-4D 3/1/06 15 7.92 643 12.90

• clear peristaltic P-4D 3/1/06 18 7.82 641 12.90

• clear peristaltic P-4D 3/7/06 8.23 15 7.18 605 12.90

• clear peristaltic P-4D 3/7/06 18 7.19 603 13.00

• clear peristaltic P-4D 3/7/06 21 7.20 602 13.00

• clear peristaltic P-5 12/1/05 6.48 10 6.79 845 14.30

• clear peristaltic P-5 12/1/05 15 6.67 800 14.90

• clear peristaltic P-5 12/1/05 22 6.65 804 15.40

• clear peristaltic P-5 1/3/06 6.45 10 7.38 675 12.60

• clear peristaltic P-5 1/3/06 15 6.96 679 13.20

• clear peristaltic P-5 1/3/06 20 6.95 686 13.20

• clear peristaltic P-5 1/3/06 25 6.94 686 13.20

• clear peristaltic P-5D 12/23/05 10.22 10 7.65 453 12.86

• clear peristaltic P-5D 12/23/05 12 7.22 457 13.11

• clear peristaltic P-5D 12/23/05 14 7.15 458 13.13

• clear peristaltic P-5D 1/3/06 8.91 15 7.71 514 13.60

• clear peristaltic P-5D 1/3/06 20 7.71 515 13.60

• clear peristaltic P-5D 1/3/06 25 7.70 520 13.60

• clear peristaltic P-6 12/1/05 7.30 10 7.15 655 13.70

• cloudy, gray peristaltic P-6 12/1/05 15 7.13 659 13.90

• slightly cloudy, gray peristaltic P-6 12/1/05 20 7.11 669 14.30

• slightly cloudy, gray peristaltic P-6 1/18/06 6.18 10 6.37 234 9.97

• clear peristaltic P-6 1/18/06 12 6.20 237 10.34

• clear peristaltic P-6 1/18/06 14 6.10 235 10.33

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 22 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-7 12/1/05 9.58 10 6.80 1257 13.70

• cloudy, gray peristaltic P-7 12/1/05 15 6.71 1272 13.90

• slightly cloudy, gray peristaltic P-7 12/1/05 20 6.74 1268 14.20

• slightly cloudy, gray peristaltic P-8 12/1/05 5.63 10 6.90 644 13.90

• slightly cloudy, gray peristaltic P-8 12/1/05 15 6.96 627 14.90

• slightly cloudy, gray peristaltic P-8 12/1/05 20 6.95 623 14.60

• slightly cloudy, gray peristaltic P-8 12/6/05 5.74 10 6.43 498 14.00 *

• peristaltic P-8 12/6/05 15 6.45 503 14.60 *

• peristaltic P-8 12/6/05 20 6.43 518 14.40 *

• peristaltic P-9 12/5/05 8.75 10 7.07 229 12.70

• slightly cloudy peristaltic P-9 12/5/05 15 6.68 229 12.10

• clear peristaltic P-9 12/5/05 20 6.64 227 12.30

• clear peristaltic P-9 12/13/05

• 10 7.04 221 13.40

• clear peristaltic P-9 12/13/05 13 6.75 220 13.30

• clear peristaltic P-9 12/13/05 16 6.51 223 12.90

• clear peristaltic P-10 12/5/05 6.54 10 8.04 466 13.90

• cloudy peristaltic P-10 12/5/05 15 8.07 451 14.10

• clear peristaltic P-10 12/5/05 20 7.96 458 13.70

• clear peristaltic P-11 12/5/05 6.55 10 7.90 645 12.60

• cloudy peristaltic P-11 12/5/05 15 7.84 640 14.10

• clear peristaltic P-11 12/5/05 20 7.74 637 13.90

• clear peristaltic P-11 12/5/05 P-12 12/5/05 6.79 10 7.90 554 12.60

• slightly cloudy peristaltic P-12 12/5/05 15 7.66 557 14.30

• clear peristaltic P-12 12/5/05 20 7.49 569 13.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 23 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-13D 12/23/05 8.34 10 8.09 812 14.10

• slightly cloudy peristaltic P-13D 12/23/05 13 7.89 809 13.90

• clear peristaltic P-13D 12/23/05 16 7.82 809 13.90

• clear peristaltic P-13D 1/3/06 8.25 10 7.70 825 14.00

• clear peristaltic P-13D 1/3/06 15 7.68 827 14.00

• clear peristaltic P-13D 1/3/06 20 7.67 827 14.00

• clear peristaltic P-13D 1/11/06 5.26 10 7.81 863 13.50

• clear peristaltic P-13D 1/11/06 13 7.72 821 13.60

• clear peristaltic P-13D 1/11/06 16 7.71 818 13.70

• clear peristaltic P-13D 1/18/06 5.20 17 6.56 1114 9.61

• clear peristaltic P-13D 1/18/06 20 6.40 1113 11.63

• clear peristaltic P-13D 1/18/06 23 6.45 1113 11.67

• clear peristaltic P-13D 1/25/06 8.16 10 7.47 790 11.70 132 slightly cloudy peristaltic P-13D 1/25/06 15 7.68 789 11.20 82.1 clear peristaltic P-13D 1/25/06 20 7.71 788 10.90 57.2 clear peristaltic P-13D 1/25/06 25 7.70 786 11.00 42.5 clear peristaltic P-13D 2/1/06 7.90 10 7.39 775 13.70

• clear peristaltic P-13D 2/1/06 13 7.20 692 14.30

• clear peristaltic P-13D 2/1/06 16 7.12 689 14.40

• clear peristaltic P-13D 2/9/06 7.98 5 6.21 1045 11.69

• clear peristaltic P-13D 2/9/06 10 6.07 1043 11.77

• clear peristaltic P-13D 2/9/06 15 6.04 1043 11.60

• clear peristaltic P-13D 2/15/06 7.99 10 7.45 664 13.00

• clear peristaltic P-13D 2/15/06 13 7.34 664 13.20

• clear peristaltic P-13D 2/15/06 16 7.26 667 13.20

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 24 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 P-13D 2/22/06 8.02 10 7.54 915 10.00

• slightly cloudy peristaltic P-13D 2/22/06 13 7.57 905 10.50

• clear peristaltic P-13D 2/22/06 16 7.46 919 10.70

• clear peristaltic P-13D 3/1/06 7.90 12 8.81 768 13.20

• clear peristaltic P-13D 3/1/06 15 8.36 769 12.50

• clear peristaltic P-13D 3/1/06 18 8.27 763 12.80

• clear peristaltic P-13D 3/7/06 7.93 10 7.90 770 13.00

• clear peristaltic P-13D 3/7/06 13 7.61 715 13.40

• clear peristaltic P-13D 3/7/06 16 7.46 708 13.10

• clear peristaltic P-13D 3/7/06 19 7.44 705 13.10

• clear peristaltic P-14 1/24/06 6.40 10 6.76 514 12.26

• clear peristaltic P-14 1/24/06 13 6.70 515 12.41

• clear peristaltic P-14 1/24/06 16 6.69 515 12.26

• clear peristaltic P-14D 1/24/06 7.89 10 7.02 509 14.48

• clear peristaltic P-14D 1/24/06 13 6.86 512 14.46

• clear peristaltic P-14D 1/24/06 16 6.79 511 14.36

• clear peristaltic S-1 12/5/05 7.50 10 7.52 377 13.10

• slightly cloudy peristaltic S-1 12/5/05 15 7.86 380 13.50

• clear peristaltic S-1 12/5/05 20 8.01 383 13.80

• clear peristaltic S-1D 1/26/06 7.87 10 8.54 306 13.80 537 cloudy peristaltic S-1D 1/26/06 15 8.45 304 13.50 521 cloudy peristaltic S-1D 1/26/06 20 8.39 307 13.20 507 cloudy peristaltic S-1D 1/26/06 25 8.36 306 13.00 503 cloudy peristaltic S-2 12/5/05 5.22 10 7.81 546 12.50

• slightly cloudy peristaltic S-2 12/5/05 15 7.62 553 12.50

• clear peristaltic S-2 12/5/05 20 7.68 553 12.50

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 25 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 S-2 1/3/06 4.68 10 7.27 630 12.15

• clear peristaltic S-2 1/3/06 13 7.25 629 12.18

• clear peristaltic S-2 1/3/06 16 7.10 628 12.20

• clear peristaltic S-2 2/1/06 3.80 10 7.10 496 12.20

• clear peristaltic S-2 2/1/06 13 7.03 497 12.20

• clear peristaltic S-2 2/1/06 16 7.01 495 12.30

• clear peristaltic S-2 2/9/06 3.98 5 10.37 689 10.37

• clear peristaltic S-2 2/9/06 10 10.36 688 10.36

• clear peristaltic S-2 2/9/06 15 10.37 688 10.37

• clear peristaltic S-2 2/15/06 4.04 10 7.09 483 11.60

• clear peristaltic S-2 2/15/06 13 7.08 483 11.60

• clear peristaltic S-2 2/15/06 16 7.07 482 11.70

• clear peristaltic S-2 2/22/06 4.08 10 7.49 649 10.20

• cloudy peristaltic S-2 2/22/06 13 7.42 642 10.20

• clear peristaltic S-2 2/22/06 16 7.43 630 10.40

• clear peristaltic S-2 3/1/06 3.91 10 7.35 532 10.60

• clear peristaltic S-2 3/1/06 13 7.34 537 10.60

• clear peristaltic S-2 3/1/06 16 7.34 535 10.70

• clear peristaltic S-2D 12/12/05 6.14 10 7.98 403 12.90

• slightly cloudy peristaltic S-2D 12/12/05 13 7.87 388 13.40

• slightly cloudy peristaltic S-2D 12/12/05 16 7.86 389 13.10

• slightly cloudy peristaltic S-2D 1/3/06 5.30 10 6.90 406 12.90

• slightly cloudy peristaltic S-2D 1/3/06 13 7.08 406 12.94

• clear peristaltic S-2D 1/3/06 16 6.98 407 12.96

• clear peristaltic S-2D 2/1/06 4.37 10 7.10 326 13.70

• clear peristaltic S-2D 2/1/06 13 7.10 325 13.80

• clear peristaltic S-2D 2/1/06 16 7.11 326 13.70

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 26 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 S-2D 2/9/06 4.56 5 6.11 427 11.88

• clear peristaltic S-2D 2/9/06 10 6.13 428 11.87

• clear peristaltic S-2D 2/9/06 15 6.13 428 11.98

• clear peristaltic S-2D 2/15/06 4.62 10 7.24 317 13.00

• clear peristaltic S-2D 2/15/06 13 7.20 318 13.20

• clear peristaltic S-2D 2/15/06 16 7.19 318 13.20

• clear peristaltic S-2D 2/22/06 4.65 10 7.62 397 11.70

• cloudy peristaltic S-2D 2/22/06 13 7.58 393 11.70

• cloudy peristaltic S-2D 2/22/06 16 7.57 398 11.80

• cloudy peristaltic S-2D 3/1/06 4.50 10 8.01 383 12.90

• clear peristaltic S-2D 3/1/06 13 8.10 362 12.00

• clear peristaltic S-2D 3/1/06 16 7.87 365 12.00

• clear peristaltic S-3 12/5/05 5.29 10 7.90 450 12.90

• clear peristaltic S-3 12/5/05 15 7.80 447 13.30

• clear peristaltic S-3 12/5/05 20 7.65 447 13.30

• clear peristaltic S-4 12/5/05 5.69 10 7.98 597 11.80

• cloudy peristaltic S-4 12/5/05 15 7.86 599 12.40

• cloudy peristaltic S-4 12/5/05 20 7.76 598 12.20

• clear peristaltic S-4D 1/26/06 7.75 10 8.10 419 12.80 63.8 slightly cloudy peristaltic S-4D 1/26/06 15 8.05 402 12.50 48.7 clear peristaltic S-4D 1/26/06 20 8.00 403 12.40 32.4 clear peristaltic S-5 12/5/05 4.25 10 8.20 392 11.10

• slightly cloudy peristaltic S-5 12/5/05 15 8.14 377 12.10

• slightly cloudy peristaltic S-5 12/5/05 20 8.07 389 12.20

• slightly cloudy peristaltic S-6 12/5/05 6.72 10 7.90 449 11.70

• slightly cloudy peristaltic S-6 12/5/05 15 7.79 454 12.40

• clear peristaltic S-6 12/5/05 20 7.75 452 12.10

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 27 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 S-7 1/24/06 4.98 10 6.64 693 9.28

• clear peristaltic S-7 1/24/06 13 6.62 698 9.26

• clear peristaltic S-7 1/24/06 16 6.61 698 9.21

• clear peristaltic S-7D 1/24/06 6.80 10 7.71 469 10.87

• clear peristaltic S-7D 1/24/06 13 7.19 471 11.05

• clear peristaltic S-7D 1/24/06 16 7.12 473 10.70

• clear peristaltic VB-1-1 11/16/05 13.30 10 7.77 1061 17.72

• clear peristaltic VB-1-1 11/16/05 12 7.68 1057 17.62

• clear peristaltic VB-1-1 11/16/05 14 7.63 1054 17.74

• clear peristaltic VB-1-1 1/4/06 13.00 5 8.06 835 13.30 *

• peristaltic VB-1-1 1/4/06 10 8.05 831 13.20 *

• peristaltic VB-1-1 1/4/06 15 8.02 827 13.40 845

• peristaltic VB-1-1D 12/16/05 12.34 13 7.47 545 13.77

• clear peristaltic VB-1-1D 12/16/05 16 7.55 554 14.20

• clear peristaltic VB-1-1D 12/16/05 19 7.56 559 14.24

• clear peristaltic VB-1-1D 1/4/06 12.30 10 7.02 644 13.62

• slightly cloudy peristaltic VB-1-1D 1/4/06 13 7.01 644 13.85

• slightly cloudy peristaltic VB-1-1D 1/4/06 16 7.00 645 13.87

• clear peristaltic VB-1-2D 1/13/06 9.40 10 7.16 636 12.72

• slightly cloudy peristaltic VB-1-2D 1/13/06 13 7.18 643 12.80

• clear peristaltic VB-1-2D 1/13/06 16 7.14 651 12.83

• clear peristaltic VB-1-3 11/16/05 11.97 10 7.33 313 13.24

• clear peristaltic VB-1-3 11/16/05 12 7.24 311 13.40

• clear peristaltic VB-1-3 11/16/05 14 7.27 312 13.43

• clear peristaltic VB-1-3D 1/13/06 9.65 10 7.20 661 12.65

• clear peristaltic VB-1-3D 1/13/06 12 7.21 654 12.60

• clear peristaltic VB-1-3D 1/13/06 15 7.21 660 12.59

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 28 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-1-4 11/16/05 10.62 10 7.44 458 13.40

• clear peristaltic VB-1-4 11/16/05 12 7.42 456 13.42

• clear peristaltic VB-1-4 11/16/05 14 7.42 454 13.22

• clear peristaltic VB-1-4D 1/13/06 8.90 25 7.07 924 10.40

• slightly cloudy peristaltic VB-1-4D 1/13/06 30 7.01 929 10.71

• clear peristaltic VB-1-4D 1/13/06 35 7.10 931 10.92

• clear peristaltic VB-1-5 11/16/05 12.52 10 6.96 770 13.52

• clear peristaltic VB-1-5 11/16/05 12 6.92 765 13.15

• clear peristaltic VB-1-5 11/16/05 14 6.92 769 13.14

• clear peristaltic VB-1-5D 1/13/06 10.29 10 8.02 562 13.20

• slightly cloudy peristaltic VB-1-5D 1/13/06 13 7.95 558 13.20

• slightly cloudy peristaltic VB-1-5D 1/13/06 16 7.92 562 13.20

• clear peristaltic VB-1-6 11/22/05 14.38 10 7.97 191 13.88

• slightly cloudy peristaltic VB-1-6 11/22/05 13 8.05 175 13.69

• clear peristaltic VB-1-6 11/22/05 16 8.07 172 13.54

• clear peristaltic VB-1-6D 1/13/06 14.30 10 8.49 271 13.80

• clear peristaltic VB-1-6D 1/13/06 13 8.49 268 13.10

• clear peristaltic VB-1-6D 1/13/06 16 8.40 267 13.10

• clear peristaltic VB-1-7 11/22/05 12.44 10 8.16 267 14.01

• slightly cloudy peristaltic VB-1-7 11/22/05 13 8.04 264 13.99

• slightly cloudy peristaltic VB-1-7 11/22/05 16 7.97 264 13.71

• clear peristaltic VB-1-7D 1/9/06 11.00 10 7.32 658 14.50

• slightly cloudy peristaltic VB-1-7D 1/9/06 13 7.19 702 14.77

• slightly cloudy peristaltic VB-1-7D 1/9/06 16 7.14 719 13.98

• clear peristaltic VB-1-8 11/22/05 12.15 10 7.05 731 12.72

• cloudy peristaltic VB-1-8 11/22/05 13 7.19 739 12.86

• cloudy peristaltic VB-1-8 11/22/05 16 7.09 744 12.84

• slightly cloudy peristaltic CRA 016841 (12)

TABLE 4.3 Page 29 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-1-8D 1/9/06 10.52 10 7.13 788 14.36

• slightly cloudy peristaltic VB-1-8D 1/9/06 13 7.07 803 14.76

• clear peristaltic VB-1-8D 1/9/06 16 7.01 801 14.05

• clear peristaltic VB-1-9 11/22/05 10.76 10 7.13 582 12.06

• cloudy peristaltic VB-1-9 11/22/05 13 7.18 572 12.37

• clear peristaltic VB-1-9 11/22/05 16 7.12 566 12.46

• clear peristaltic VB-1-9D 1/13/06 10.91 10 7.42 423 11.20

• clear peristaltic VB-1-9D 1/13/06 13 7.42 440 11.35

• clear peristaltic VB-1-9D 1/13/06 16 7.39 442 11.30

• clear peristaltic VB-2-1 11/15/05 14.87 10 7.94 146 13.90

• slightly cloudy peristaltic VB-2-1 11/15/05 12 8.49 142 14.13

• clear peristaltic VB-2-1 11/15/05 14 8.51 140 14.11

• clear peristaltic VB-2-2 11/15/05 8.80 10 7.32 593 14.07

• clear peristaltic VB-2-2 11/15/05 12 7.28 593 13.83

• clear peristaltic VB-2-2 11/15/05 14 7.27 593 13.79

• clear peristaltic VB-2-2 12/5/05 8.89 10 7.24 472 11.60 *

• peristaltic VB-2-2 12/5/05 15 7.31 480 11.70 *

• peristaltic VB-2-2 12/5/05 20 7.32 488 11.90 *

• peristaltic VB-2-2 1/4/06 8.60 15 7.47 468 10.60 17.2 clear peristaltic VB-2-2 1/4/06 18 7.38 476 10.70 12.8 clear peristaltic VB-2-2 1/4/06 21 7.32 473 10.60 9.5 clear peristaltic VB-2-2 1/4/06 24 7.28 477 10.70 8.6 clear peristaltic VB-2-2D 12/23/05 8.00 10 7.41 429 11.33

• clear peristaltic VB-2-2D 12/23/05 12 7.37 430 11.33

• clear peristaltic VB-2-2D 12/23/05 14 7.40 431 11.33

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 30 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-2-2D 1/4/06 7.83 5 7.21 355 11.50 42.8 cloudy peristaltic VB-2-2D 1/4/06 8 7.20 357 11.60 36.4 cloudy peristaltic VB-2-2D 1/4/06 11 7.19 353 11.80 29.1 cloudy peristaltic VB-2-3 11/15/05 9.03 10 6.80 574 13.22

• clear peristaltic VB-2-3 11/15/05 12 6.82 572 13.23

• clear peristaltic VB-2-3 11/15/05 14 6.83 569 13.23

• clear peristaltic VB-2-4 11/15/05 10.00 10 7.61 455 13.42

• slightly cloudy peristaltic VB-2-4 11/15/05 12 7.57 458 13.45

• slightly cloudy peristaltic VB-2-4 11/15/05 14 7.50 456 13.16

• clear peristaltic VB-2-5 11/15/05 9.20 10 6.65 585 12.99

• clear peristaltic VB-2-5 11/15/05 12 6.66 585 13.27

• clear peristaltic VB-2-5 11/15/05 14 6.65 584 13.28

• clear peristaltic VB-2-5 1/3/06 9.30 10 6.44 657 9.09

• clear peristaltic VB-2-5 1/3/06 12 6.42 656 9.10

• clear peristaltic VB-2-5 1/3/06 14 6.42 657 9.06

• clear peristaltic VB-2-5D 12/14/05 6.02 27 7.29 443 11.00

• clear peristaltic VB-2-5D 12/14/05 30 7.27 444 10.75

• clear peristaltic VB-2-5D 12/14/05 33 7.27 444 10.49

• clear peristaltic VB-2-5D 1/3/06 6.61 10 6.70 495 11.80

• clear peristaltic VB-2-5D 1/3/06 12 6.72 495 11.81

• clear peristaltic VB-2-5D 1/3/06 14 6.76 497 11.81

• clear peristaltic VB-2-6 11/15/05 10.80 10 6.42 472 13.67

• clear peristaltic VB-2-6 11/15/05 12 6.17 470 13.66

• clear peristaltic VB-2-6 11/15/05 14 6.14 470 13.65

• clear peristaltic VB-2-6 12/5/05 10.93 10 6.50 430 12.20 *

• peristaltic VB-2-6 12/5/05 15 6.48 430 11.90 *

• peristaltic VB-2-6 12/5/05 20 6.51 420 12.10 *

• peristaltic CRA 016841 (12)

TABLE 4.3 Page 31 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-2-6 1/3/06 7.94 5 7.47 433 11.10 48.4 cloudy peristaltic VB-2-6 1/3/06 8 7.10 279 11.10 39.8 clear peristaltic VB-2-6 1/3/06 11 6.91 416 11.10 26.2 clear peristaltic VB-2-6 1/3/06 14 7.18 426 11.20 20.9 clear peristaltic VB-2-6 1/3/06 17 7.14 420 11.10 18.5 clear peristaltic VB-2-6 1/3/06 20 7.11 408 11.20 16.7 clear peristaltic VB-2-6D 12/14/05 6.12 30 7.62 263 11.43

• slightly cloudy peristaltic VB-2-6D 12/14/05 33 7.61 265 11.65

• slightly cloudy peristaltic VB-2-6D 12/14/05 36 7.63 264 11.65

• clear peristaltic VB-2-6D 1/3/06 6.11 5 6.92 252 12.30 33.8 clear peristaltic VB-2-6D 1/3/06 8 7.02 242 12.40 27.4 clear peristaltic VB-2-6D 1/3/06 11 7.11 244 12.70 23.6 clear peristaltic VB-2-6D 1/3/06 14 7.12 238 12.80 20.1 clear peristaltic VB-2-7 12/14/05 11.19 2 8.55 170 12.65

• clear peristaltic VB-2-7 12/14/05 5 8.20 175 12.70

• clear peristaltic VB-2-7 12/14/05 8 8.20 175 12.63

• clear peristaltic VB-2-7 1/4/06 10.99 15 7.36 144 12.40 13.6 clear peristaltic VB-2-7 1/4/06 18 7.41 139 12.70 10.8 clear peristaltic VB-2-7 1/4/06 21 7.41 142 12.80 8.2 clear peristaltic VB-2-7D 12/14/05 11.39 33 8.09 212 12.18

• clear peristaltic VB-2-7D 12/14/05 36 8.01 211 12.21

• clear peristaltic VB-2-7D 12/14/05 39 7.95 214 12.34

• clear peristaltic VB-2-7D 1/4/06 11.26 5 7.43 148 13.00 29.3 clear peristaltic VB-2-7D 1/4/06 8 7.41 149 13.30 22.7 clear peristaltic VB-2-7D 1/4/06 11 7.40 149 13.20 16.9 clear peristaltic VB-2-8 12/14/05 8.27 12 7.95 262 13.41

• clear peristaltic VB-2-8 12/14/05 15 7.82 262 12.69

• clear peristaltic VB-2-8 12/14/05 18 7.85 262 12.42

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 32 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-2-9 1/12/06 8.49 10 6.70 501 13.01

• slightly cloudy peristaltic VB-2-9 1/12/06 13 6.39 509 12.93

• slightly cloudy peristaltic VB-2-9 1/12/06 16 6.22 509 12.31

• clear peristaltic VB-2-9D 1/12/06 9.69 10 7.17 313 14.10

• cloudy peristaltic VB-2-9D 1/12/06 13 7.18 313 14.07

• cloudy peristaltic VB-2-9D 1/12/06 16 7.16 310 14.07

• cloudy peristaltic VB-3-1 11/15/05 9.83 10 7.29 608 14.10

• clear peristaltic VB-3-1 11/15/05 12 7.24 607 14.02

• clear peristaltic VB-3-1 11/15/05 14.00 7.23 608 14.01

• clear peristaltic VB-3-2 11/15/05 10.22 10 7.04 1002 14.69

• clear peristaltic VB-3-2 11/15/05 12 7.02 997 14.66

• clear peristaltic VB-3-2 11/15/05 14 6.99 994 14.68

• clear peristaltic VB-3-3 11/16/05 9.05 10 6.44 951 12.43

• clear peristaltic VB-3-3 11/16/05 12 6.39 949 12.54

• clear peristaltic VB-3-3 11/16/05 14 6.30 936 12.45

• clear peristaltic VB-3-4 11/16/05 10.58 10 5.94 907 12.13

• clear peristaltic VB-3-4 11/16/05 12 5.84 900 12.13

• clear peristaltic VB-3-4 11/16/05 14 5.80 898 12.16

• clear peristaltic VB-3-4 11/16/05 VB-3-4 11/16/05 VB-3-4 12/5/05 10.43 10 6.34 680 9.50 *

• peristaltic VB-3-4 12/5/05 15 6.36 670 9.70 *

• peristaltic VB-3-4 12/5/05 20 6.29 684 9.80 *

• peristaltic VB-3-4 1/3/06 10.33 10 5.96 875 8.51

• clear peristaltic VB-3-4 1/3/06 13 5.82 880 8.47

• clear peristaltic VB-3-4 1/3/06 16 5.73 886 8.49

• clear peristaltic CRA 016841 (12)

TABLE 4.3 Page 33 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-3-4D 12/14/05 9.79 40 7.62 333 12.03

• clear peristaltic VB-3-4D 12/14/05 43 7.60 334 11.97

• clear peristaltic VB-3-4D 12/14/05 47 7.60 334 11.97

• clear peristaltic VB-3-4D 1/3/06 9.57 10 7.05 357 11.82

• clear peristaltic VB-3-4D 1/3/06 13 7.06 358 11.87

• clear peristaltic VB-3-4D 1/3/06 16 7.05 358 11.79

• clear peristaltic VB-3-5 11/22/05 9.44 10 7.28 272 13.43

• cloudy peristaltic VB-3-5 11/22/05 13 7.27 146 13.72

• cloudy peristaltic VB-3-5 11/22/05 16 7.33 261 13.73

• slightly cloudy peristaltic VB-3-6 11/22/05 8.60 10 7.24 757 12.38

• cloudy peristaltic VB-3-6 11/22/05 13 7.12 777 12.75

• slightly cloudy peristaltic VB-3-6 11/22/05 16 6.93 779 12.79

• clear peristaltic VB-3-7 12/2/05 8.19 10 7.66 203 11.30

• cloudy peristaltic VB-3-7 12/2/05 15 7.09 195 11.40

• cloudy peristaltic VB-3-7 12/2/05 20 6.94 194 11.50

• cloudy peristaltic VB-3-7 12/14/05 5.72 15 7.74 232 11.72

• clear peristaltic VB-3-7 12/14/05 18 7.71 231 11.66

• slightly cloudy peristaltic VB-3-7 12/14/05 21 7.68 231 11.62

• slightly cloudy peristaltic VB-3-7 1/3/06 7.91 10 6.76 243 9.27

• clear peristaltic VB-3-7 1/3/06 13 6.25 242 9.10

• clear peristaltic VB-3-7 1/3/06 16 6.12 241 9.09

• clear peristaltic VB-3-7D 1/3/06 5.45 10 7.34 252 11.56

• clear peristaltic VB-3-7D 1/3/06 13 7.27 251 11.58

• clear peristaltic VB-3-7D 1/3/06 16 7.23 250 11.60

• clear peristaltic VB-3-8 12/2/05 8.20 10 8.09 313 11.80

• cloudy peristaltic VB-3-8 12/2/05 15 8.15 318 11.10

• cloudy peristaltic VB-3-8 12/2/05 20 8.15 304 12.30

• cloudy peristaltic CRA 016841 (12)

TABLE 4.3 Page 34 of 34

SUMMARY

OF MONITORING WELL PURGING PARAMETERS EXELON GENERATION BRAIDWOOD STATION Well Water Minutes pH Conductivity Temperature Turbidity Observations Pump Type Identifier Date Level Purged (Std. Units) (µS/cm) 1 (°C) (ntu) 2 VB-3-9D 12/13/05 6.37 35 7.64 700 10.70

• cloudy peristaltic VB-3-9D 12/13/05 38 7.50 710 10.30

• cloudy peristaltic VB-3-9D 12/13/05 41 7.39 726 10.36

• cloudy peristaltic VB-3-9D 1/4/06 5.64 10 7.27 550 11.90 36.2 cloudy peristaltic VB-3-9D 1/4/06 13 7.22 549 12.20 28.4 cloudy peristaltic VB-3-9D 1/4/06 16 7.17 550 12.40 21.5 cloudy peristaltic VB-3-10 12/16/05 8.22 15 7.42 258 10.03

• cloudy peristaltic VB-3-10 12/16/05 20 7.39 154 10.10

• cloudy peristaltic VB-3-10 12/16/05 24 7.25 172 9.37

• cloudy peristaltic VB-3-10 1/3/06 7.88 15 7.17 683 10.90 24.4 clear peristaltic VB-3-10 1/3/06 18 7.18 684 11.00 20.7 clear peristaltic VB-3-10 1/3/06 21 7.16 686 11.00 17.2 clear peristaltic VB-3-10D 12/16/05 7.28 20 7.35 579 10.51

• clear peristaltic VB-3-10D 12/16/05 23 7.37 585 10.83

• clear peristaltic VB-3-10D 12/16/05 25 7.32 574 *

• clear peristaltic VB-3-10D 1/3/06 7.07 10 7.19 540 12.40 57.1 cloudy peristaltic VB-3-10D 1/3/06 13 7.18 543 12.50 42.3 cloudy peristaltic VB-3-10D 1/3/06 16 7.18 542 12.30 28.9 clear peristaltic 1

ft BTOC - feet below top of casing 2

mS/cm - millisiemens per centimeter 3

NTU - nephelometric turbidity units 4

• - Not measured CRA 016841 (12)

TABLE 4.4

SUMMARY

OF PRIVATE WATER WELLS DOWNGRADIENT OF THE SITE EXELON GENERATION BRAIDWOOD STATION Location Name / Elev Rate Record Number Total Depth Address Driller Drill Date Record Type Use Well Type Aquifer Type Stat LVL Pump LVL Status (Ft) Elev Ref Formation Top Bottom (gpm)

REC-222 14 281 Carol Lane, Braidwood owner 01/24/1992 Construction Report Domestic Driven Unconsolidated 9 14 WATER 0 - gravel 10 14 0 REC-237 14 270 Carol Lane owner 4/6/1992 Construction Report Domestic Driven Unconsolidated - - WATER 0 - 4 sand point 10 14 0 REC-191 19 300 Francis, Braidwood owner 11/27/1991 Construction Report Domestic Driven Unconsolidated - - WATER 0 - sand 0 19 0 PW-3 20 W. Smiley - - - - - - - - - - - Shallow - - -

REC-62 27 50' N line, 2650' W line Section 17, T. 32N., R. 9E. Bolliger, John & Sons - - - - - - - WATER 0 - - 0 0 -

PW-8 28 S. Center St. - - - - - - - - - - - Shallow bedrock - - -

PW-2 31 25131 W. Smiley Rd., Braidwood Strange, Robert E. 1/6/2005 Construction Report Domestic Drilled Unconsolidated 7 9 WATER 0 - sand/gravel 21 31 15 PW-1 32 25141 W. Smiley Rd, Braidwood Strange, Robert E. 1/6/2005 Construction Report Domestic Drilled Unconsolidated 7 9 WATER 0 - sand & gravel 22 32 15 PW-13 33 34714 Comet Dr. - - - - - - - - - - - - - - -

REC-314 38 160 Bobby Lane, COMET ESTES. Strange, Robert E. 7/6/2000 Construction Report Domestic Drilled Unconsolidated 19 29 WATER 0 - sand/gravel 33 38 10 REC-40 40 Route 113 and Park Road, Braidwood. Knierin Paul 01/25/1972 Construction Report Domestic - - - - WATER 0 - limestone 10 40 20 REC-151 40 - Anderson Well Drlg. - - - - - - - WATER 0 - - 0 0 -

PW-15 40 S. Center St. - - - - - - - - - - - Shallow sand - - -

PW-7 40 380 Comet Dr. - - - - - - - - - - - Shallow sand - - -

REC-221 48 306 Comet Dr., Braidwood Wills, Elmer D. 5/6/1991 Construction Report Domestic - Bedrock 8 - WATER 0 - sand rock 32 48 0 REC-239 50 34420S Charles Lane, Braidwood Brown, Darwin 10/21/1994 Construction Report Domestic Drilled Bedrock 9 39 WATER 0 - shale 10 50 0 REC-65 56 330'S line, 330'W line section 17, T.32N., R. 9E. Miller, J. P. Art. Well 7/00/1955 Construction Report Test Well - Bedrock - - WATER 0 - - 0 0 -

REC-180 60 Lot 27-28 Comet Estates Subd. Fykes, Charles N. 11/26/1986 Construction Report Domestic - - - - WATER 0 - sandstone 38 60 10 PW-14 60 S. Center St. - - - - - - - - - - - - - - -

PW-9 60 S. Center St. - - - - - - - - - - - - - - -

REC-67 65 - Layne Western Co., Inc. - - - - - - - WATER 0 - - 0 0 -

REC-158 65 Cemetery Road, Braidwood Fykes Charles & Pump 7/8/1978 Construction Report Domestic - - - - WATER 0 - sandstone 35 65 8 REC-201 65 - Fykes, Charles N. 07/27/1984 Construction Report Domestic - - - - WATER 593 GL sandstone 38 65 10 REC-61 75 50' N line, 1300' W line Section 17, T. 32N., R. 9E. Bolliger, John & Sons 04/00/1950 Construction Report Test Well - Bedrock - - WATER 0 - - 0 0 -

REC-73 75 Route #1 Braceville Lockport Well & Pump 2/9/1971 Construction Report Domestic - - - - WATER 0 - sandstone 43 75 10 REC-63 79 30' W line, 1800' N line Section 17, T. 32N., R. 9E. Bolliger, John & Sons - - - - - - - WATER 0 - - 0 0 -

REC-64 80 330'S line, 330'E line of NW NW section 17, T.32N., R. 9E. Miller, J. P. Art. Well 07/001955 Construction Report Test Well - Bedrock - - WATER 0 - - -

REC-99 80 311 W. Odell St. Lockport Well & Pump 12/2/1973 - - - - - - WATER 0 - limestone 50 80 10 REC-104 86 - Griffy, Cecil D. - - - - - - - WATER 0 - shale 61 86 4 REC-107 90 - Lockport Well & Pump - - - - - - - WATER 0 - sandstone 46 90 10 REC-159 100 Cemetary Road, Braidwood Fykes Charles & Pump 04/20/1978 Construction Report Domestic - - - - WATER 0 - sandstone 40 65 10 REC-66 106 - Miller, J. P. Art. Well - - - - - - - WATER 0 - - 0 0 -

REC-241 110 LOT 57 Fordonski, Keith 11/11/1994 Construction Report Domestic Drilled Bedrock 49 59 WATER 0 - shale 45 110 0 REC-277 125 360 Cemetary Rd, Braidwood Bisping, Calvin 8/10/1996 Construction Report Domestic Drilled Bedrock 20 100 WATER 0 - limestone - shale 60 125 0 REC-268 350 LOT 22 FAIR OAKS Fordonski, Keith - - - - - - - WATER 0 - shale & limestone 60 350 0 REC-275 470 LOT 21 FAIR OAKS SUBD. Fordonski, Keith 10/21/1996 Construction Report Domestic Drilled Bedrock 49 449 WATER 0 - limestone 260 470 0 PW-11 675 34711 S. Center St., Braidwood Edward Hall - Web Well & Pump 11/20/2001 Construction Report Domestic Drilled Bedrock 295 339 WATER 0 - sand 655 675 12 PW-10 680 38038 S. Center St., Braidwood Matherly, Hubert 01/28/1999 Construction Report Domestic Drilled Bedrock 339 379 WATER 0 - St. Peter 615 680 0 REC-2 1647 - Varner C W - - - - - - - WATER 577 GL - 0 0 -

PW-12 - 376 Comet Dr. - - - - - - - - - - - Shallow bedrock - - -

PW-4 - S. Center St. - - - - - - - - - - - - - - -

PW-5 - 388 Comet Dr. - - - - - - - - - - - - - - -

PW-6 - - - - - - - - - - - - - Shallow sand - - -

REC-37 - - Griffy, Cecil D. 5/11/1973 Construction Report Domestic - - - - WATER 0 - limestone, shale 71 80 20 CRA 016841 (12)

TABLE 6.1

SUMMARY

OF GENERAL WATER QUALITY IN BLOWDOWN LINE AND BACKGROUND GROUNDWATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Blowdown Line Unimpacted Groundwater Sample Location: At River Inside Plant MW-106 MW-110 Sample ID: GW-111405-DC-004 GW-111405-DC-001 GW-111405-DC-003 GW-111405-DC-002 Sample Date: Illinois Standards 11/14/2005 11/14/2005 11/14/2005 11/14/2005 Units Class I Wet Alkalinity mg/L - 320 300 170 570 Chloride mg/L 200c 96 100 ND(5) ND(5)

Nitrate mg/L 10.0c 0.14 0.12 0.28 0.21 Phosphate (as PO4) mg/L - 0.92 0.86 0.06 ND(0.01)

Phosphorous mg/L - 0.3 0.28 0.02 ND(0.01)

Sulfide mg/L - ND(0.05) ND(0.05) ND(0.05) ND(0.05)

Metals Aluminum mg/L - 0.21 0.018 0.015 0.1 Antimony mg/L 0.006 c ND(0.006) ND(0.006) ND(0.006) ND(0.006)

Arsenic mg/L 0.05c 0.006 ND(0.002) ND(0.002) 0.007 Barium mg/L 2.0c 0.034 0.035 0.016 0.098 Beryllium mg/L 0.004 c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Boron mg/L 2.0c 0.36 0.35 0.03 0.26 Cadmium mg/L 0.005 c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Calcium mg/L - 155 156 52.7 193 Chromium mg/L 0.1c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Cobalt mg/L 1.0c ND(0.001) ND(0.001) ND(0.001) 0.005 Copper mg/L 0.65c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Iron mg/L 5.0c 0.17 0.17 0.01 6.31 Lead mg/L 0.0075 c ND(0.002) ND(0.002) ND(0.002) ND(0.002)

Magnesium mg/L - 78.5 77.7 18.8 30.9 Manganese mg/L 0.15c 0.018 0.019 0.056 ND(0.001)

Molybdenum mg/L - 0.01 0.01 ND(0.01) ND(0.01)

Nickel mg/L 0.1c 0.007 ND(0.001) ND(0.001) 0.003 Potassium mg/L - 9.5 9.5 1.9 25.3 Selenium mg/L 0.05c ND(0.002) ND(0.002) ND(0.002) ND(0.002)

Silver mg/L 0.05c ND(0.001) ND(0.001) ND(0.001) ND(0.001)

Sodium mg/L - 48.4 48.1 2.70 4.9 Thallium mg/L 0.002 c ND(0.002) ND(0.002) ND(0.002) ND(0.002)

Vanadium mg/L 0.049 ND(0.01) ND(0.01) ND(0.01) ND(0.01)

Zinc mg/L 5.0c ND(0.005) ND(0.005) 0.029 0.017 c

Value listed is also the Groundwater Quality Standard for this chemical pursuant to 35 Ill. Adm. Code 620.410 for Class I Groundwater or 35 Ill. Adm. Code 620.420 for Class II Groundwater.

Exceeds Illinois Standards Class I CRA 016841 (12)

TABLE 6.2 Page 1 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

A-1 1/11/2006 33 A-1D 1/11/2006 60 B-01 2/20/2006 64 B-01D 2/20/2006 46 BL-01 11/17/2005 70 BL-02 11/17/2005 156 BL-03 11/18/2005 0 BL-04 11/18/2005 40 BL-05 11/18/2005 102 BL-06 11/18/2005 114 BL-07 11/18/2005 39 BL-08 11/18/2005 90 BL-09 12/23/2005 4701 BL-09 1/11/2006 5270 BL-09 1/18/2006 5049 BL-09 1/25/2006 4809 BL-09 2/1/2006 4689 BL-09 2/9/2006 4932 BL-09 2/15/2006 4393 BL-09 2/22/2006 4086 BL-09 3/1/2006 3404 BL-09 (recount) 3/1/2006 3486 BL-09D 12/23/2005 23097 BL-09D 1/11/2006 22016 BL-09D 1/18/2006 21230 BL-09D 1/25/2006 20383 BL-09D 2/1/2006 20171 BL-09D 2/9/2006 20428 BL-09D 2/15/2006 19778 BL-09D 2/22/2006 18018 BL-09D 3/1/2006 16980 BL-09D (recount) 3/1/2006 16403 BL-10 11/17/2005 295 BL-10 1/4/2006 -104 BL-10D 12/15/2005 8259 BL-10D (recount) 12/15/2005 7885 BL-10D 1/4/2006 7535 BL-11 11/17/2005 61 BL-11 1/3/2006 13 BL-11D 12/15/2005 -213 BL-11D 1/3/2006 -27 BL-12 11/17/2005 126 BL-12 1/3/2006 -39 BL-12D 12/15/2005 -31 BL-12D 1/3/2006 -35 BL-13 11/17/2005 76 CRA 016841 (12)

TABLE 6.2 Page 2 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

BL-13 1/3/2006 -16 BL-13D 12/15/2005 -150 BL-13D 1/3/2006 9 BL-14 11/17/2005 70 BL-14 1/3/2006 -37 BL-14D 12/15/2005 -187 BL-14D 1/3/2006 -91 BL-15 11/17/2005 1178 BL-15 1/3/2006 146 BL-15D 12/16/2005 -38 BL-15D 1/3/2006 -49 BL-16 11/17/2005 4058 BL-16 1/3/2006 3364 BL-16D 12/16/2005 -85 BL-16D 1/3/2006 -91 BL-17 12/1/2005 25 BL-17 12/5/2005 105 BL-17 12/6/2005 183 BL-17 1/3/2006 -44 BL-17D 12/12/2005 28 BL-17D 1/3/2006 -126 BL-18 12/1/2005 108 BL-18D 2/7/2006 121 BL-19 12/1/2005 37 BL-19D 2/7/2006 95 BL-20D 12/23/2005 -76 BL-20D 1/4/2006 -117 C-1 12/12/2005 85 C-1 1/3/2006 -80 C-1D 12/12/2005 158 C-1D 1/3/2006 -140 C-2 1/24/2006 -48 C-2 2/1/2006 105 C-2 2/9/2006 162 C-2 2/15/2006 38 C-2 2/22/2006 82 C-2D 1/24/2006 147 C-2D 2/1/2006 221 C-2D 2/9/2006 320 C-2D 2/15/2006 351 C-2D 2/22/2006 589 D-1 12/6/2005 92 D-1 1/4/2006 -13 D-1D 12/23/2005 -147 D-1D 1/4/2006 -141 D-2 12/5/2005 125 CRA 016841 (12)

TABLE 6.2 Page 3 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

D-2 12/6/2005 59 D-2 1/4/2006 -165 D-2D 12/23/2005 -91 D-2D 1/4/2006 -36 D-3 12/2/2005 137 D-3 1/4/2006 -168 D-3D 12/23/2005 4674 D-3D 1/4/2006 5110 D-4 12/6/2005 91 D-5 12/2/2005 73 Ditch at Culvert 12/22/2005 1007 Ditch at Culvert 2/15/2006 468 Ditch at Culvert 2/22/2006 306 Ditch at Culvert 3/1/2006 670 Ditch by Alpha Gate 1/12/2006 -30 Ditch by Alpha Gate 1/19/2006 107 Ditch by Alpha Gate 1/26/2006 77 Ditch by Alpha Gate 2/2/2006 23 Ditch by Alpha Gate 2/9/2006 201 Ditch by Alpha Gate 2/16/2006 123 Ditch by GW-1 2/15/2006 36 Ditch by GW-1 2/22/2006 100 Ditch by GW-1 3/1/2006 -10 DS-10 5/20/2005 49 DS-11 5/5/2005 28 DS-11 5/27/2005 ND()

DS-1a 5/10/2005 44 DS-1b 5/10/2005 10 DS-1b 5/27/2005 40 DS-1b 7/14/2005 59 DS-1b 9/22/2005 -2.34 DS-2 5/5/2005 438 DS-2 5/27/2005 682 DS-2 7/14/2005 1690 DS-2 9/22/2005 1740 DS-3 5/27/2005 786 DS-3 6/14/2005 35 DS-3 7/14/2005 226 DS-3 9/22/2005 289 DS-4 6/14/2005 99 DS-4 7/14/2005 -22.6 DS-4 9/22/2005 72.3 DS-5 7/14/2005 -46.2 DS-5 9/22/2005 -41.1 DS-6 5/20/2005 65 DS-7 5/27/2005 78 CRA 016841 (12)

TABLE 6.2 Page 4 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

DS-8 5/10/2005 51 DS-8 5/27/2005 166 DS-9 5/20/2005 65 F-1 12/12/2005 104 F-1 1/3/2006 -44 F-1D 12/12/2005 139 F-1D 1/3/2006 -56 F-2D 1/9/2006 684 F-2D 1/12/2006 546 F-3D 1/9/2006 1689 F-3D 1/12/2006 1689 F-4D 1/24/2006 -22 F-5D 1/24/2006 1512 F-6D 1/24/2006 689 F-7D 1/24/2006 575 F-8D 1/24/2006 872 G-1 12/6/2005 133 G-2 12/6/2005 87 G-2D 1/26/2006 67 G-3 12/6/2005 81 GW-1 2/9/2006 20 GW-2 2/9/2006 57 MW-101 3/24/2005 41 MW-101 7/28/2005 -397 MW-101 10/19/2005 -52.8 MW-101 11/15/2005 157 MW-102 3/24/2005 58 MW-103 3/24/2005 132 MW-103 8/15/2005 3010 MW-103 10/20/2005 2660 MW-103 11/15/2005 2497 MW-104 3/24/2005 397 MW-104 7/28/2005 142 MW-105 7/28/2005 563 MW-105 10/17/2005 384 MW-105 11/15/2005 729 MW-105 1/4/2006 169 MW-105D 12/16/2005 -69 MW-105D 1/4/2006 -120 MW-106 7/28/2005 8.77 MW-106 1/4/2006 -35 MW-106D 12/16/2005 -115 MW-106D 1/4/2006 -25 MW-107 7/28/2005 158 MW-107 9/30/2005 124 MW-107 10/17/2005 129 CRA 016841 (12)

TABLE 6.2 Page 5 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

MW-107 11/15/2005 269 MW-108 7/28/2005 18.2 MW-108 9/30/2005 43.8 MW-108 10/17/2005 -29.4 MW-108 11/15/2005 91 MW-109 7/28/2005 238 MW-109 9/30/2005 305 MW-110 10/20/2005 137 MW-110 11/15/2005 93 MW-110 1/4/2006 -104 MW-111 10/19/2005 -44.0 MW-111 11/15/2005 224 MW-111 1/4/2006 -78 MW-111D 1/9/2006 -66 MW-112 10/19/2005 -33.0 MW-112 11/15/2005 167 MW-112 1/4/2006 -127 MW-112D 1/9/2006 -111 MW-113 10/19/2005 4480 MW-113 11/15/2005 4830 MW-113 12/5/2005 4009 MW-113 12/6/2005 3598 MW-113 1/3/2006 4008 MW-113D 12/14/2005 4835 MW-113D 1/3/2006 4772 P-1 12/1/2005 2484 P-2 12/2/2005 4344 P-2 1/3/2006 2045 P-2D 12/12/2005 2599 P-2D 1/3/2006 2384 P-3 12/2/2005 3258 P-4 12/1/2005 33041 P-4 12/6/2005 25311 P-4 1/3/2006 19317 P-4 1/11/2006 15937 P-4 1/18/2006 12165 P-4 1/25/2006 9588 P-4 2/1/2006 6621 P-4 2/9/2006 4412 P-4 2/15/2006 3045 P-4 3/1/2006 3479 P-4D 12/23/2005 59592 P-4D 1/3/2006 48493 P-4D 1/11/2006 47095 P-4D 1/18/2006 50308 P-4D 1/25/2006 38965 CRA 016841 (12)

TABLE 6.2 Page 6 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

P-4D 2/1/2006 32551 P-4D 2/9/2006 34828 P-4D 2/15/2006 39339 P-4D 2/22/2006 44547 P-4D 3/1/2006 45640 P-4D (recount) 3/1/2006 40895 P-4S 2/22/2006 2841 P-5 12/1/2005 6621 P-5 1/3/2006 6166 P-5D 12/23/2005 2402 P-5D 1/3/2006 2165 P-6 12/1/2005 450 P-6 1/18/2006 110 P-7 12/1/2005 1210 P-8 12/1/2005 2998 P-8 12/6/2005 2212 P-9 12/5/2005 1346 P-9 12/6/2005 -90 P-9 12/13/2005 111 P-9 (recount) 12/13/2005 27 P-10 12/5/2005 1934 P-10 12/6/2005 1723 P-11 12/5/2005 1681 P-11 12/6/2005 1476 P-12 12/5/2005 1535 P-12 12/6/2005 1622 P-13D 12/23/2005 226468 P-13D (recount) 12/28/2005 225231 P-13D 1/3/2006 228283 P-13D 1/11/2006 229838 P-13D 1/18/2006 223754 P-13D 1/25/2006 217122 P-13D 2/1/2006 226034 P-13D 2/9/2006 233668 P-13D 2/15/2006 229926 P-13D 2/22/2006 230133 P-13D 3/1/2006 230793 P-13D (recount) 3/1/2006 214892 P-14 1/24/2006 2537 P-14D 1/24/2006 2388 PS-1 12/22/2005 -18 PS-1 1/4/2006 -89 PS-2 12/22/2005 -89 PS-2 1/4/2006 15 PS-3 1/4/2006 -137 PS-4 1/10/2006 30 CRA 016841 (12)

TABLE 6.2 Page 7 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

PS-6 1/12/2006 287 RW-1 12/1/2005 2396 RW-1 12/4/2005 7855 RW-2 12/1/2005 33736 RW-2 12/4/2005 88778 RW-2 (10 ft) 12/13/2005 54111 RW-2 (10.6 ft) 12/6/2005 58621 RW-2 (20 ft) 12/13/2005 171166 RW-2 (20.6 ft) 12/6/2005 170024 RW-2 (25 ft) 12/6/2005 223888 RW-2 (25 ft) 12/13/2005 246442 RW-3 12/2/2005 197 RW-4 12/2/2005 380 S-1 12/5/2005 -21 S-1 12/6/2005 83 S-1D 1/26/2006 1287 S-2 12/5/2005 95 S-2 12/6/2005 88 S-2 1/3/2006 62 S-2 2/1/2006 183 S-2 2/9/2006 237 S-2 2/15/2006 190 S-2 2/22/2006 172 S-2 3/1/2006 85 S-2D 12/12/2005 225 S-2D 1/3/2006 -2 S-2D 2/1/2006 193 S-2D 2/9/2006 177 S-2D 2/15/2006 185 S-2D 2/22/2006 168 S-2D 3/1/2006 74 S-3 12/5/2005 145 S-3 12/6/2005 57 S-4 12/5/2005 1280 S-4 12/6/2005 1086 S-4D 1/26/2006 2111 S-5 12/5/2005 2023 S-5 12/6/2005 1874 S-6 12/5/2005 679 S-6 12/6/2005 411 S-7 1/24/2006 1373 S-7D 1/24/2006 1546 SG-1 7/28/2005 61.3 SG-2 7/28/2005 1970 SG-3 7/28/2005 -21.4 SW-1 11/30/2005 2464 CRA 016841 (12)

TABLE 6.2 Page 8 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

SW-2 11/30/2005 2347 SW-2 1/11/2006 2938 SW-2 1/18/2006 2504 SW-2 1/25/2006 2441 SW-2 2/1/2006 2626 SW-2 2/15/2006 2434 SW-2 2/22/2006 808 SW-2 3/1/2006 2243 SW-2 (recount) 3/1/2006 2142 SW-3 12/2/2005 96 SW-4 12/2/2005 83 SW-5 1/30/2006 76 SW-6 2/9/2006 41 VB-1 5/27/2005 51295 VB-1-1 11/15/2005 1194 VB-1-1 1/4/2006 425 VB-1-1D 12/16/2005 -49 VB-1-1D 1/4/2006 -132 VB-1-2 11/17/2005 337 VB-1-2D 1/13/2006 238 VB-1-3 11/15/2005 206 VB-1-3D 1/13/2006 19431 VB-1-4 11/15/2005 384 VB-1-4D 1/13/2006 7424 VB-1-5 11/15/2005 130 VB-1-5D 1/13/2006 22928 VB-1-6 11/22/2005 95 VB-1-6D 1/13/2006 41 VB-1-7 11/22/2005 140 VB-1-7D 1/9/2006 -116 VB-1-8 11/22/2005 57 VB-1-8D 1/9/2006 10877 VB-1-9 11/22/2005 107 VB-1-9D 1/13/2006 3370 VB-2-1 11/15/2005 207 VB-2-2 11/15/2005 6193 VB-2-2 12/5/2005 5832 VB-2-2 12/6/2005 5569 VB-2-2 1/4/2006 5232 VB-2-2D 12/23/2005 3445 VB-2-2D 1/4/2006 4037 VB-2-3 11/15/2005 3940 VB-2-4 11/15/2005 3664 VB-2-5 11/15/2005 4270 VB-2-5 1/3/2006 3834 VB-2-5D 12/14/2005 64 CRA 016841 (12)

TABLE 6.2 Page 9 of 9

SUMMARY

OF TRITIUM CONCENTRATIONS IN 1

MONITORING WELLS AND SURFACE WATER SAMPLES EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

VB-2-5D 1/3/2006 102 VB-2-6 11/15/2005 2132 VB-2-6 12/5/2005 2348 VB-2-6 12/6/2005 1979 VB-2-6 1/3/2006 1412 VB-2-6D 12/14/2005 56 VB-2-6D 1/3/2006 44 VB-2-7 12/14/2005 -47 VB-2-7 1/4/2006 -60 VB-2-7D 12/14/2005 -52 VB-2-7D 1/4/2006 -53 VB-2-8 12/14/2005 -103 VB-2-9 1/12/2006 78 VB-2-9D 1/12/2006 -65 VB-3 5/11/2005 1521 VB-3-1 11/15/2005 5959 VB-3-10 12/16/2005 8473 VB-3-10 1/3/2006 12076 VB-3-10D 12/16/2005 70773 VB-3-10D 1/3/2006 108736 VB-3-2 11/15/2005 32830 VB-3-2 (repeat) 11/15/2005 26686 VB-3-3 11/16/2005 43894 VB-3-4 11/16/2005 58489 VB-3-4 12/5/2005 43708 VB-3-4 12/6/2005 40654 VB-3-4 1/3/2006 29286 VB-3-4D 12/14/2005 747 VB-3-4D 1/3/2006 790 VB-3-5 11/22/2005 95 VB-3-6 11/22/2005 53572 VB-3-7 12/2/2005 169 VB-3-7 1/3/2006 -126 VB-3-7D 12/14/2005 -79 VB-3-7D 1/3/2006 -205 VB-3-8 12/2/2005 171 VB-3-9D 12/13/2005 21715 VB-3-9D 1/4/2006 19605 1

Results through March 1, 2006 CRA 016841 (12)

TABLE 6.3 Page 1 of 2

SUMMARY

OF WEEKLY RESULTS FOR TRITIUM IN KEY MONITORING WELLS 1

AND THE PERIMETER DITCH EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

BL-09 12/23/2005 4701 BL-09 1/11/2006 5270 BL-09 1/18/2006 5049 BL-09 1/25/2006 4809 BL-09 2/1/2006 4689 BL-09 2/9/2006 4932 BL-09 2/15/2006 4393 BL-09 2/22/2006 4086 BL-09 3/1/2006 3404 BL-09 (recount) 3/1/2006 3486 BL-09D 12/23/2005 23097 BL-09D 1/11/2006 22016 BL-09D 1/18/2006 21230 BL-09D 1/25/2006 20383 BL-09D 2/1/2006 20171 BL-09D 2/9/2006 20428 BL-09D 2/15/2006 19778 BL-09D 2/22/2006 18018 BL-09D 3/1/2006 16980 BL-09D (recount) 3/1/2006 16403 C-2 1/24/2006 -48 C-2 2/1/2006 105 C-2 2/9/2006 162 C-2 2/15/2006 38 C-2 2/22/2006 82 C-2D 1/24/2006 147 C-2D 2/1/2006 221 C-2D 2/9/2006 320 C-2D 2/15/2006 351 C-2D 2/22/2006 589 Ditch by Alpha Gate 1/12/2006 -30 Ditch by Alpha Gate 1/19/2006 107 Ditch by Alpha Gate 1/26/2006 77 Ditch by Alpha Gate 2/2/2006 23 Ditch by Alpha Gate 2/9/2006 201 Ditch by Alpha Gate 2/16/2006 123 P-4 12/1/2005 33041 P-4 12/6/2005 25311 P-4 1/3/2006 19317 P-4 1/11/2006 15937 P-4 1/18/2006 12165 P-4 1/25/2006 9588 P-4 2/1/2006 6621 P-4 2/9/2006 4412 P-4 2/15/2006 3045 P-4 3/1/2006 3479 P-4D 12/23/2005 59592 P-4D 1/3/2006 48493 CRA 016841 (12)

TABLE 6.3 Page 2 of 2

SUMMARY

OF WEEKLY RESULTS FOR TRITIUM IN KEY MONITORING WELLS 1

AND THE PERIMETER DITCH EXELON GENERATION BRAIDWOOD STATION Monitoring Location Sample Date Tritium Result (pCi/L)

P-4D 1/11/2006 47095 P-4D 1/18/2006 50308 P-4D 1/25/2006 38965 P-4D 2/1/2006 32551 P-4D 2/9/2006 34828 P-4D 2/15/2006 39339 P-4D 2/22/2006 44547 P-4D 3/1/2006 45640 P-4D (recount) 3/1/2006 40895 P-13D 12/23/2005 226468 P-13D (recount) 12/28/2005 225231 P-13D 1/3/2006 228283 P-13D 1/11/2006 229838 P-13D 1/18/2006 223754 P-13D 1/25/2006 217122 P-13D 2/1/2006 226034 P-13D 2/9/2006 233668 P-13D 2/15/2006 229926 P-13D 2/22/2006 230133 P-13D 3/1/2006 230793 P-13D (recount) 3/1/2006 214892 S-2 12/5/2005 95 S-2 12/6/2005 88 S-2 1/3/2006 62 S-2 2/1/2006 183 S-2 2/9/2006 237 S-2 2/15/2006 190 S-2 2/22/2006 172 S-2 3/1/2006 85 S-2D 12/12/2005 225 S-2D 1/3/2006 -2 S-2D 2/1/2006 193 S-2D 2/9/2006 177 S-2D 2/15/2006 185 S-2D 2/22/2006 168 S-2D 3/1/2006 74 SW-2 11/30/2005 2347 SW-2 1/11/2006 2938 SW-2 1/18/2006 2504 SW-2 1/25/2006 2441 SW-2 2/1/2006 2626 SW-2 2/15/2006 2434 SW-2 2/22/2006 808 SW-2 3/1/2006 2243 SW-2 (recount) 3/1/2006 2142 1

Results through March 1, 2006 CRA 016841 (12)

TABLE 6.4

SUMMARY

OF TRITIUM CONCENTRATIONS IN PRIVATE WELLS 1 EXELON GENERATION BRAIDWOOD STATION Monitoring Location Date Tritium Result (pCi/L)

PW-1 11/30/2005 -26 PW-2 11/30/2005 48 PW-3 11/30/2005 25 PW-3 2/2/2006 -63 PW-4 12/2/2005 43 PW-5 12/7/2005 9 PW-5 1/19/2006 -12 PW-5 1/30/2006 28 PW-6 2/2/2006 -4 PW-6P2 12/8/2005 142 2

PW-6P 2/7/2006 128 PW-7 12/7/2005 -58 PW-8 12/3/2005 1151 PW-8 12/6/2005 1524 PW-8 12/8/2005 1367 PW-9 12/5/2005 142 PW-10 12/7/2005 72 PW-11 12/5/2005 99 PW-11 2/2/2006 12 PW-12 12/7/2005 44 PW-13 12/7/2005 -62 PW-13 1/30/2006 38 PW-14 12/14/2005 -118 PW-14 1/30/2006 56 PW-15 12/14/2005 -51 1

Results through March 1, 2006 2

Surface water (pond) sample CRA 016841 (12)

TABLE 6.5

SUMMARY

OF INDICATOR PARAMETER SAMPLES IN THE BLOWDOWN LINE, BACKGROUND GROUNDWATER, AND MONITORING WELLS NEAR THE BLOWDOWN LINE EXELON GENERATION BRAIDWOOD STATION Monitoring Location: Sample Date: Sodium (mg/L) Chloride (mg/L)

At River (blowdown line) 11/14/2005 48.4 96 Inside Plant (blowdown line) 11/14/2005 48.1 100 MW-106 (unimpacted) 11/14/2005 2.70 ND(5)

MW-110 (unimpacted) 11/14/2005 4.9 ND(5)

BL-01 11/18/2005 2.5 ND(5)

BL-02 11/18/2005 3.3 6 BL-03 11/18/2005 2.8 ND(5)

BL-04 11/18/2005 4.3 ND(5)

BL-05 11/18/2005 5.7 8 BL-06 11/18/2005 2.8 ND(5)

BL-07 11/18/2005 2.8 16 BL-08 11/18/2005 1.6 ND(5)

BL-10 11/18/2005 10.8 ND(5)

BL-10D 12/15/2005 22.6 26 BL-11 11/18/2005 2.3 ND(5)

BL-11D 12/15/2005 4.7 6.0 BL-12 11/18/2005 2.6 ND(5)

BL-12D 12/15/2005 3.5 5.0 BL-13 11/18/2005 2.1 ND(5)

BL-13D 12/15/2005 2.8 ND(5)

BL-14 11/18/2005 2.6 ND(5)

BL-14D 12/15/2005 3.0 5.0 BL-15 11/18/2005 8.9 6 BL-15D 12/16/2005 3.0 ND(5)

BL-16 11/18/2005 2.6 54 BL-16D 12/16/2005 2.4 ND(5)

BL-17D 12/13/2005 3.5 ND(5)

MW-105D 12/16/2005 2.6 5.0 CRA 016841 (12)

APPENDIX A CORRESPONDENCE BETWEEN EXELON AND THE IEPA BUREAU OF WATER 016841 (12)

axc000 Generation Company? L.L.C wwwexeioncorn.com Exelcs;n Nh ir]

Braidwood. Station 35100 South Rt 53, Suite 84 Braseviiie, C 6o4o7qClg February 2, 2006 BWO6001 1 Ms. Beverly Booker Illinois Environmental Protection Agency Bureau of Water, CAS #19 P.O. Box 19276 Springfield, IL 62794-9276

Subject:

Braidwood Station Response to Violation Notice W-2005-00537

Reference:

Letter from Illinois EPA, Violation Notice: Exelon Generation Braidwood Station, dated December 16, 2005

Dear Ms. Booker:

In the referenced letter, the Illinois Environmental Protection Agency (Illinois EPA) issued a Violation Notice to Exelon Generation Company, LLC (Exelon) regarding groundwater quality at Braidwood Station and adjoining property. The Violation Notice is based on sampling results obtained between December 1 and December 12, 2005, that indicate the level of tritium exceeds the standards set forth in Section 12 of the Illinois Environmental Protection Act and the Illinois Pollution Control Boards regulations.

The enclosure to this letter contains Exelons response to the Violation Notice. The response describes our actions to protect and inform the public, cease the release of tritium to groundwater, prevent future release of tritium to the groundwater, and our plans to address the elevated levels of tritium in the existing groundwater.

In accordance with 415 ILCS 5/31, Notice; complaint; hearing; subdivision (a)(2)(C), Exelon requests a meeting with representatives of the Illinois EPA to discuss this matter. We will contact the Illinois EPA to arrange this meeting.

This written response is being submitted within 45 days of Exelons receipt of the Violation Notice via certified mail (i.e., December 20, 2005). By submitting this response, Exelon is not admitting that it has violated the Illinois Environmental Protection Act or the regulations of the Illinois Pollution Control Board. If you have any questions about this response, please contact Kenneth Ainger at 630 657-2800.

Respectfully, Keith J. PoIson Site Vice President Braidwood Station VIA CERTIFIED MAIL RETURN RECEIPT REQUESTED

ENCLOSURE RESPONSE TO VIOLATION NOTICE W-2005-00537 I. Violation Notice Allegations On December 16, 2005, the Illinois EPA issued the following in a violation notice to Exelon Generation Company, LLC:

Groundwater Quality No person shall cause, threaten, or allow the release of any contaminant to resource groundwater such that treatment or additional treatment is necessary to continue an existing use or to assure a potential use of such groundwater, or such that the existing or potential use of such groundwater is precluded. Exelon Generation Braidwood Station must cease and decease of any further violations of the Act.

Violation Violation Date Descriøtion 12/12/05 Sampling results indicate violations of Section 12 of the Act, the General Prohibition Against Use Impairment of Resource Groundwater, and the causing of the groundwater quality standard of tritium (20,000 pCi/L) to be exceeded during the time period and at the location(s) designated below:

RW-2 10.5 ft. depth 58,621 pCI/L RW-2 20.5 ft. depth 170,024 pCi/L RW-2 25 ft. depth 223,888 pCi/L Rule/Reg. Section 12(a), and (d) of the Act, 415 ILCS 5112, 35 III. Adm. Code 620.115, 35 III. Adm. Code 620.301(a)(1) and (2), and 35 III. Adm. Code 620.41 0(e)(3).

12/07/05 Sampling results indicate violations of Section 12 of the Act, the General Prohibition Against Use Impairment of Resource Groundwater during the time period and at the location(s) designated below:

Private well located at horse barn North of pond 1,151 pCi/L Rule/Reg. Section 12(a), and (d) of the Act, 415 ILCS 5/12, 35 III. Adm. Code 620115, and 35 ii. Adrn. Code 620.301(a)(1) and (2).

12/06/05 Sampling results indicate violations of Section 12 of the Act, the General Prohibition Against Use Impairment of Resource Groundwater, and the causing of the groundwater quality standard of tritium (20,000 pCl/L) to be exceeded during the time period and at the location(s) designated below:

VB-3-4 58,489 pCi/L VB-3-3 43,894 pCi/L VB-3-2 32,830 pCi/L VB-3-6 53,572 pCi/L P-4 33,736 pCi/L RW-2 33,736 pCi/L

Rule/Reg. Section 12(a), and (d) of the Act, 415 ILCS 5/12,35 III. Adm. Code 620.115,35111, Adm. Code 620.301(a)(1)and (2), and 35111. Adm. Code 620.41 0(e)(3).

Violation Violation Date DescriDtion 12/01/05 Sampling results indicate violations of Section 12 of the Act, the General Prohibition Against Use Impairment of Resource Groundwater during the time period and at the location(s) designated below:

Pond located just north of Smiley Rd. and west of the 2,347 pCl/L blow-down line. 2,464 pCi/L Rule/Reg. Section 12(a), (d), and (f) of the Act, 415 ILCS 5/12.

II. Exelon Response The following response describes our actions to protect and inform the public, cease the release of tritium to groundwater, prevent future release of tritium to the groundwater, and our plans to address the elevated levels of tritium in the existing groundwater. In order to further assist the Illinois EPA in an understanding of site conditions, we are including in Attachment 1 a summary of key investigative data collected to date at the site, These data summaries are considered preliminary, as we are collecting additional data and continuing our evaluations, and include:

1. A base map of monitoring locations and key site features.

2. Groundwater level contour maps of the shallow and deep zones of the upper aquifer.

3. Estimated tritium concentrations presented in contour maps of the shallow and deep zones,

4. A hydrogeologic cross-section.

5. A table summarizing permanent and temporary well monitoring specifications.

6. A table summarizing sample results for tritium analyses from wells in the site area; and

7. A table summarizing tritium results from samples collected at private wells.

Protection and Notification of the Public Exelons first priority in response to this issue is the protection of the public. When we determined in late November 2005 that tritium in groundwater had likely migrated off the Braidwood Station property, we notified potentially affected residents. Door-to-door initial notifications were made to inform them of the status of our investigation, present them a fact sheet from the U. S. EPA regarding tritium, offer to sample their private wells for the presence of tritium, and respond to their questions and concerns. The results of the private well sample analyses, conducted by an independent laboratory, were provided to the residents. On December 12, 2005, Exelon conducted a meeting with the potentially affected local residents to update them on the status of our ongoing investigation, explain future actions and address their questions and concerns. In addition, we have met individually with a number of residents to address specific 2

concerns. A second round of door-to-door updates was conducted with the potentially affected residents on December 29, 2005, during which we provided those residents a copy of our December 29, 2005 news release and invited them to another update meeting which was held on January 26, 2006.

In addition to sampling private wells, Exelon obtained permission from potentially affected residents to drill temporary wells on their property and to sample water from ponds on their property to determine the migration of the tritium in groundwater.

Exelons plume characterization team continued sampling, analyzing and notifying adjoining land owners until the leading edge of the tritium was identified. Exelon has sampled over 31 private wells, drilled and sampled over 150 monitoring wells on and off the property, and sampled nearby surface water ponds offsite to laterally and vertically identify the distribution of tritium in the groundwater.

In order to identify potential users of groundwater in the down-gradient direction of flow (which is to the north) from the blowdown pipeline, Exelon initiated a comprehensive well inventory and well records search. This search is being conducted through the Illinois State Water Survey and includes groundwater users that can be identified within a one mile radius of the blowdown pipeline. The location of the wells, their use, depth and construction are being compiled for future evaluations. This well inventory, along with previously identified well users (private residences where wells have already been sampled), will form the basis of Exelons notification list. This list will identify additional private, as well as public, water supply users that would be notified if it is determined there is a potential for impact to their water supply wells.

Cessation of Release of Tritium to Groundwater Liquid radioactive effluent releases into the Braidwood Station circulating water blowdown line were suspended on November 23, 2005. This action was taken until additional information could be collected and testing conducted to ensure the integrity of the pipeline at all locations. Braidwood Station has not processed any liquid radioactive effluents through the circulating water blowdown pipeline since November 23, 2005.

As a result of suspending liquid radioactive effluent releases into the circulating water blowdown pipeline, temporary 20,000 gallon water storage tanks are being used to store liquid radioactive effluents onsite until new radioactive waste processing equipment is made operational.

An acoustical leak detection test was completed on January 6, 2006 to verify the integrity of the circulating water blowdown pipeline. A tethered acoustical sensor head inserted into the pipe was carried by the circulating water blowdown flow providing leak detection as it traversed along the pipeline length. The sensitivity of the sensor was determined by Exelon Engineering to detect a one gallon per minute leak under normal operating blowdown line pressure. One anomaly was identified at the end of the pipeline near the Kankakee River. This area was excavated and a visual inspection of the exposed pipe determined there was no leak.

Although there have been no liquid radioactive effluent releases through the circulating water blowdown pipeline since November 23, 2005, because the vacuum breaker valves installed along the length of the blowdown pipeline have been a source of leaks and 3

spills, a daily visual inspection of the blowdown pipeline is being conducted to verify no gross leakage.

In addition, Exelon has completed the following activities.

• Installation and sampling of over 30 shallow (approximately 15 ft. deep) and over 20 deep (approximately 25 ft. deep) monitoring points adjacent to the blowdown pipeline.

• Laboratory analyses of over 60 samples for tritium as a direct indicator of leakage from the blowdown pipeline and 45 samples for chloride and sodium which have been established as an indicator of the Braidwood Station cooling lake water flowing in the blowdown pipeline.

• Measurement of water levels along the blowdown pipeline and comparison with the regional, shallow groundwater table to determine if significant leaks are creating a mounding effect on the water table.

• Comparison of the three dimensional distribution of tritium in the groundwater to the plumes located south of Smiley Road to determine if it correlates with an on-going, or active release from the blowdown pipeline.

The above activities have relied upon groundwater data collected to date near and down-gradient of the blowdown pipeline. None of the data have indicated to Exelon and to its hydrogeologic experts that tritium measured in the groundwater on and off property has come from an active leak in the circulating water blowdown pipeline or vacuum breakers.

Prevention of Future Release of Tritium to Groundwater Exelon is taking several actions, as described below, to prevent future releases of tritium into the groundwater. These include a potential design change involving discharge of liquid effluent into an additional circulating water blowdown pipeline, a project to significantly reduce the overall liquid discharge of tritium from Braidwood Station, and, in the event of a future spill, procedure changes to create a more effective response to minimize the impact to the environment.

Liquid effluents will not be introduced into the current circulating water blowdown pipeline unless leakage from this pipeline and vacuum breaker valves can be prevented with a high level of confidence. Exelon is currently exploring options for an alternate pipeline for discharge of liquid radioactive effluents that would maintain the current discharge point, but eliminate concerns with the existing circulating water blowdown pipeline and vacuum breaker valves.

Additionally, a project is underway at Braidwood Station to minimize liquid radioactive effluent releases into the circulating water blowdown pipeline in the future with the installation of new water processing equipment in the radioactive waste system. These improvements include state-of-the-art technologies in reverse osmosis and an additional unit to recycle existing liquid radioactive waste inventory into water that meets our quality requirements for the reactor coolant system. Also, Braidwood Station intends to install a means of converting liquid effluents to gaseous effluents.

4

Exelon is also looking into methods of reducing the production of tritium through various changes in reactor core configuration and primary water chemistry. These include potential changes in the reactor fuel rod design, burnable poisons in the reactor core, and fuel cycle length. Exelon is also partnering with its vendors to explore possible new technologies in tritium separation.

Finally, in the event of a future spill, the following actions are being taken to improve Exelons response and minimize the impact to the environment.

1. A corporate environmental manager was assigned the action to institutionalize Exelons tritium environmental spill response knowledge. The manager will utilize input from the various functional areas to develop an integrated set of procedures to mitigate and remediate spills with the potential to contain radioactive isotopes. Appropriate personnel will be trained on these procedures.

A review of the effectiveness of the procedure development and training will be conducted at a suitable interval following completion.

2. The knowledge of Braidwood Station personnel regarding environmental regulations and reporting requirements will be enhanced with additional training.

Training programs for personnel in the Operations, Chemistry/Environmental, and Radiation Protection Departments will be analyzed to determine additional knowledge requirements to address lOw level radioactivity spill reporting and personnel will be trained and tested on the changes. General training for all employees will be reviewed to identify any needed changes.

3. Exelons applicable procedures/programs will be reviewed to ensure the Illinois regulations governing radioactive contamination of groundwater are correctly reflected and implemented in those documents.

Plans to Address Elevated Levels of Tritium in Existing Groundwater Exelon proposes to address the elevated levels of tritium in existing groundwater through the Illinois EPAs Site Remediation Program (SRP). Participation in the SRP will include the following.

1. Conduct of a focused site investigation to characterize the extent of contamination. The investigation will focus on tritium. Since November 2005, Exelon has conducted extensive sampling as described above, and is currently evaluating the results to determine if additional sampling is necessary. A well survey, as described above, consistent with SRP rules and Illinois EPA policy, will also be included. Prior to submitting the final Site Investigation Report, Exelon will contact the Illinois EPA SRP staff to obtain input on any additional needs. The Site Investigation Report will be submitted as soon as possible, but no later than March 24, 2006.

2. Development of remedial objectives. As part of this step, Exelon will not only evaluate compliance with Part 620.41 0(e)(3), but risk to the public as well.

Work on developing a Remedial Objectives Report (ROR) will commence as soon as possible, and will be submitted no later than 30 days after Illinois EPA approval of the Site Investigation Report.

5

3. Preparation of a Remedial Action Plan. Based on the results of the Site Investigation and the Remedial Objectives Report, a Remedial Action Plan (RAP) will be prepared and submitted. Options are currently being evaluated which include pumping areas of high concentration and returning these waters to the circulating water system. The RAP will include a schedule for all activities from startup to completion, and also provide for quarterly reports.

This plan will be submitted within 30 days of approval of the Remedial Objectives Report.

4. Submission of a Remedial Action Completion Report (RACR). Once the RAP is approved, the final remedial design will commence within 30 days and the final RACR will be submitted within 30 days of completion.

The site has not yet been precisely identified, but generally is shown as the area on figures 4 and 5. Areas separate from this site, to the east along the routing of the blowdown pipeline, are currently being investigated.

As part of the overall strategy to address this issue, a community relations plan is being implemented. The plan builds on Braidwood Stations existing community outreach program that has been used, as described above in this response, to conduct multiple communications to keep the public informed. Exelon intends to continue this effort.

The community relations plan includes development of a website with access to a fact sheet on the Braidwood tritium issue, a telephone hotline for interested members of the public to acquire information on the issue, and an upcoming community information night. The actions in our community relations plan may be adjusted overtime, as the circumstances of this issue evolve. Our current community relations action plan will be submitted by March 1, 2006.

6

Attachment 1 Summary of Key Investigative Data Figure 1 Groundwater Monitoring Locations Figure 2 Average Groundwater Contours Shallow January 2006 Figure 3 Average Groundwater Contours DeepJanuary 2006 Figure 4 Estimated Tritium Results Shallow Groundwater Zone Figure 5 Estimated Tritium Results Deep Groundwater Zone Figure 6 Site Specific Hydrogeologic Profile Table 1 Monitoring Well Construction Specifications Table 2 Summary of Tritium Results in Monitoring Wells Table 3 Summary of Tritium Results at Private Wells

DRAFT Page 1 of 6 TABLE I MONITORING WELL CONSTRUCTION SPECiFICATIONS EXELON GENERATION BRAID WOOD STATiON Well Boring Ground Well Well Screen Top of Riser Screen Top Screen Bottom Stick Number Total Depth Surface Diameter Material interval Elevation Elevation Elevation tip 2

(ft BGS) (NGVD) (inches) ~ft805) (NGVD) (NOV13) (NGVD) (ft 405)

MW-101 10.0 599.49 2 pvc3 5 tolD 602.77 59449 58949 3.28 MW-102 11 .0 602.42 2 PVC 6 to 11 605.70 596.42 591.42 3.28 MW-103 8.0 595.72 2 PVC 3to8 598.84 592.72 587.72 3.12 MW-104 8.0 596.60 2 pvc 3 to 8 598.80 593.60 588.60 220 Mw-los 16.0 597.29 2 ~vc 11 to 16 600.74 586.29 581.29 345 MW-1OSD 24.0 597.22 1 pvc J9 to 24 598.20 578.22 573.22 0.98 MW-106 16.0 599h0 2 pvc II to 16 602.73 588.60 581o0 3.13 Mw-1o61) 27.0 59970 1 pvc 22 to 27 601.81 577.70 572.70 2.11 MW-107 16.0 59985 2 pvc 11 to 16 603.24 588.85 583.85 3.39 Mw-108 16.0 59976 2 pvc ii to 16 603.10 588.76 583.76 3.34 MW-109 16.0 59881 2 pvc ii to 16 601.23 587.81 582.81 2.42 MW-I 10 20.0 60401 3 pvc 9,5 to 19.5 607.27 594.01 584.01 3.26 MW-lU 16.0 60329 4 pvc 5.5 to 15.5 607.20 597.29 587.29 3.91 MW-lIlt) 26.5 60317 1 pvc 21.5 to 26.5 605.05 581.67 576.67 1.88 Mw-112 16.0 598.57 5 pvc 5.5 to 15.6 602.62 592.57 582.57 4.05 Mw-II2D 26.5 59861 1 pvc 21.5 to 26.5 600.85 577.11 572.11 2.24 MW-113 16.0 59610 6 pvc 5.51o15.7 599.77 590.10 580.10 3.67 MW-113D 24.0 59614 1 ~vc 19 to 24 596.90 577i4 57114 0.76 VB-2-1 15.0 601.27 1 Pvc 10 to 15 605.71 591.27 586.27 444 vB-2-2 15.0 596.82 1 pvc 10 to 15 600.16 586.82 581.82 3.34 vB-2-21) 29.5 596.49 i pvc 24.5to29.5 598.95 571.99 566.99 246

\B-2-3 15.0 595.95 1 pvc io to 15 600.16 585.95 580.95 4,21 vB-2-4 15.0 596.08 i pvc lOto 15 600.82 586.08 581.08 4.74 VB-2-5 15,0 595.76 1 pvc 10 to 15 599.82 585.76 580.76 4.06 vB-Z-SD 24.0 595.76 1 pvc t9to24 596.78 576.76 571.76 1.02 VB-2-6 15.0 596.01 1 pvc 10 to 15 601.44 586.01 581.01 543 VB-2-6D 24.0 596.01 i pvc 19 to 24 596.77 577.01 572,01 0.76 vB-2-7 15.0 600.51 1 ~vc 10 to 15 602.04 590.51 585.51 1.53 CRA ft,84 1 Presentation 3 - TI

DRAFT Page2of6 TABLE I MONITORING WELL CONSTRUCTION SPECIFICATIONS EXELON GENERATION BRAID WOOD STATION Well Boring Ground Well Well Screen Top ofRiser Screen Top Screen Bottom Stick Nu,nber Total Depth Surface Diameter Material Interval Elevation Elevation Elevation Up 1

(ft BGS) (NGVD) (inches) (ft BGS) (NGVD) (NGVD) (NO Vt)) (ft 405)

VB-2-71) 25.0 600.51 1 PVC 20 to 25 602.28 580.51 575,51 1.77 vB-2-8 15.0 598.18 1 ~vc 10 to 15 599.05 588.18 583.18 0.87 vB-2-9 14.0 i pvc 9to 14 *

• v13-2-9D 28.0 1 Pvc 23 to 28 *

• VB-3-1 15.0 596.38 1 pvc lOto 15 600.99 586.38 581.38 4.61 vs-3-2 15.0 596.49 1 pvc 10 to 15 601.51 586.49 581.49 5.02 VB-3-3 15.0 596.27 1 ~vc 10 to 15 600.03 586.27 581.27 3.76 vB-3-4 15.0 596.18 1 pvc 10 to 15 601.37 586.18 581.18 5.19 vB-3-4D 25.0 596.18 1 ~vc 20to25 600.82 576.18 571.18 4.64 15.0 - i pvc lOto 15 * *

• vB-3-6 15.0 1 ~vc 10 to 15 * *

• vB-3-7 14.5 596.24 1 Pvc 9.5 to 14.5 599.49 586.74 581.74 3.25 vB-3-71) 24.0 596.24 1 ~vc 19 to 24 597.04 577.24 572.24 0.80 VB-3-8 14.5 596.44 1 ~vc 9.5 to 14.5 599.51 586.94 581.94 3.07 vB-3-91) 24.5 595.68 1 pvc 19.5 to 24.5 596.62 577.18 57218 0.94 vB-3-io 13.0 596.43 1 ~vc 8 to 13 599.28 58843 583.43 2.85 vB-3-loD 23.5 596.49 pvc 18.5 to 23.5 598.44 577.99 572.99 1.95 yB-i-I 15.0 602.14 ~vc 10 to 15 605.62 592.14 587.14 3.48 yB-I-ID 32.0

• I pvc 27 to 32

• 9 vB-1-2 15.0 599.94 1 ~vc 10 to 15 604.65 589.94 584.94 4,71 vB-1-2D 28.0 i ~vc 23 to 28 * * *

• vB-1-3 15.0 599.64 1 ~vc 10 to 15 603.61 589.64 584.64 3.97 yB-i-3D 27.5

• j pvc 22.5 to 27.5 * * *

• vB-i-4 15.0 599.32 1 ~vc lOto 15 601.50 589.32 584.32 2.18 vB-1-4D 28.0

• 1 pvc 23 to 28 * * *

• vs-i-s 15.0 600-17 j pvc jo to 15 603.85 590.17 585.17 3.68

~B-1-5D 28.0

• I pvc 23 to 28 * * *

• vB-i-6 15.0

• 1 pvc 10 to 15 60534 * *

• CRA 10841 Presentation 3.- TI

DRAFT Page3of6 TABLE I MONITORING WELL CONSTRUCTION SPECIFICATIONS EXELON GENERATION BRA!DWOOD STATION Well Boring Ground Well Well Screen Top ofRiser Screen Top Screen Bottom Stick Number Total Depth Suiface Diameter Material Interval Elevation Elevation Elevation Up 2

(ft B(S) (NOV13) (inches) (ft BGS) (NOW)) (NOV13) (NGVD) (ft 405) vB-1-6D 27.0 1 pyc 22 to 27 * * *

• y13-1-7 15.0 i pvc: 10 to 15 603.62 * *

• VB-I-7D 26.5 600.48 1 pvc 21.5 to 26.5 602.80 578.98 573.98 2.32 VS-I-S 15.0 ~- pvc 10 t~15 603.36 * *

• VS-I-SD 26.5 600.15 1 pvc 21.5 to 26.5 602.49 578.65 573.65 2.34 vB-l-9 150

• i pvc io to 15 601.86 * *

• vB-1-9r) 27.0

• 1 pvc 22 to 27 * * *

• RW-l 25.0 596.68 I pvc 5 to 25 599.36 591.68 572 2.68 RW-2 24.0 596.59 1 pvc 4 to 24 599.30 591.59 571.59 2.71 RW-3 24.0 596.24 i pvc 4 to 24 599.19 592.24 572.27 2.95 RW-4 24.0 596.31 1 pvc 4 to 24 598.77 592.31 572.3 2.46 BL-1 17.0 600.38 i pvc 12 to 17 605.58 588.38 583.38 5.20 BL-2 14.5 600.16 1 ~vc 9.5 to 14.5 604.84 590.66 585.66 4.68 BL-3 23.0 600.60 1 pvc IS to 23 604.50 582.60 577.60 3.90 I3L-4 14,5 599.76 1 rvc lOto 15 601.91 589.76 584.76 2.15 BL-5 21.0 599.76 i pvc I6to21 602.60 583.76 578.76 2.84 BL-6 165 597.74 i pvc 11.5 to 16.5 601.83 586.24 581.24 4.09 BL-7 14.0 ~ pvc 9 to 14 601.08 588.57 583.57 3.51 BL-8 18.0 598.53 i pvc 13 totS 602.29 585.53 580.53 3.76 B1.-9~ 12.5 ~ i pvc 7,5 to 12.5 602.75 59225 587.25 3.00 BL-9 21.0 599.60 i pvc 16 to 21 602.49 583.60 578.60 2.89 BL-9D 29.0 59965 pvc 24 to 29 600.36 575.65 570.65 0.71 BE-lU 17.0 60249 i pvc 12 to 17 605.37 590.28 585.28 2.88 BL-IOD 32.0 60243 i pvc 27 to 32 605.16 575.43 570.43 2.73 BL-l 1 16.5 59747 i pvc 11.5 to 16.5 600.65 585.97 580.97 3.18 BL-1 11) 28.0 ~ pvc 23 to 28 599.09 574.34 569.34 1.75 BL-12 17.0 59803 1 pvc 12 to 17 601.60 586.03 581.03 3.57 BLr12D 28,0 59810 1 pvc 23 to 28 599.87 575.10 570.10 1.77 CRa\ 10841 Presei ta lion 3 TI

DRAFT Page4ofó TABLE 1 MONITORING WELL CONSTRUCTION SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Well Boring Ground Well Well Screen Top ofRiser Screen Top Screen Bottom Stick Number Total Depth Suiface Diameter Material Interval Elevation Elevation Elevation Up 2

(ft BOS) (NOW)) (inches) (ft BGS) (NOVD) (NOV13) (NGVD) (ft 405)

B[.-13 15.0 598.07 1 pvc 10 to 15 601.37 588.07 583.07 3.30 BL-I3D 24.5 598.05 1 ~vc 19.5 to 24.5 600.82 565.55 564.55 2.77 BL-l4 18.0 597.34 1 ~vc 13 to 18 601.26 584.34 579.34 3.92 BL-141) 26.5 59746 1 pvc 21.5 to26.5 59990 575.96 570.96 2.44 BE-IS 17.5 597.29 1 ~vc 12.5 to 17.5 600.98 584.79 579.79 3.69 BE-iSO 24.0 597.54 1 pvc 19 to 24 598.50 575.54 573.64 0.96 BL-I6 17.0 597.12 i pvc I2to 17 60030 585.12 580.12 318 BL-16D 24.0 597.28 1 ~vc 19 to 24 595.17 578.28 573.28 0.89 BL-17 14.5 597.01 1 ~vc 9.5 to 14.5 597.62 587.51 582.51 0.61 BL-I7D 24.0 597W 1 pvc 19 to 24 598.11 575.01 573.01 1.10 BE-iS 14.5 596.82 1 ~vc 9.5 to 14.5 597.59 587.32 582.32 0.77 BL-19 9.0 594.94 1 ~vc 4 to9 595.55 590.94 585.94 0.61 BL-20D 28.0 596.89 1 ~vc 23 to 28 60045 573.89 568.89 3.56 P-I 14.5 594.90 1 pvc 9,5 TO 14.5 595.59 585.40 580,40 0.69 P-2 14.5 595.65 1 ~vc 9.5 TO 14.5 596.27 586.15 58115 0.62 P-2D 23.5 595.88 1 vvc 18.5 to 23.5 596.55 577.38 572.38 0.67 l-3 14.5 595.69 1 ~vc 9.5 TO 14.5 596.26 586.19 581.19 0.57 P-I 14.9 * ~vc 9.5 TO 14.5 597.14 * *

• P-4D 27.0 596.46 i ~vc 22 to 27 599.22 574.46 569.46 2.76 pS 15.0 i pvc: 10 to 15 597.06 * *

• p-Sf) 27.0 596.34 pvc 22 to 27 599.37 574.34 569.34 3.03 P-6 14.5 1 pvc 9,5 to 14.5 597.85 * *

• P-7 145 599.77 1 ~vc 9.5 to 145 600.24 590.27 585.27 0.47 P-8 14.5 ~ i pvc 9.5 to 14.5 596.24 585.99 580.99 0.75 P-9 14.5 598.55 1 pvc 95 to 14.5 599.19 559.05 584.05 0.64 P-lU 14.5 596.08 pvc 9,5 to 14.5 596.58 586.58 581.58 0.50 P-Il 14.5 59519 i ~vc 9.5 to 14.5 596.23 585.69 580.69 1.04 p-12 14.5 595.56 1 pvc 9,5 to 14.5 596.13 586.06 581.06 0.57 CR A 10841 Pre*eotatioo 3 TI

DRAFT PageSof6 TABLE I MONITORING WELL CONSTRUCTION SPECIFICATIONS EXELON GENERATION BRAID WOOD STATION Well Boring Ground Well Well Screen Top ofRiser Screen Top Screen Bottom Stick Number Total 1)epth Surface Diameter Material Interval Elevation Elevation Elevation Up 2

(ft BOB) (NOW)) (inches) (ft BOS) (NOW)) (NOV13) (NOV17) (ftA OS)

P-13D 27.0 59611 -i pvc 22 to 27 598.76 574.11 569.11 2.65 P-14 155 i pvc ios to 15.5 * * *

• P-14D 28.0 a i pvc 23 to 28 * * *

• D-i 15.0 599.64 i pvc 10 to 15 603.69 589.64 584.64 4.05 D-lt) 27.0 599.82 i pvc 22 to 27 603.77 577.82 572.82 3.95 D-2 15.0 598.78 1 pvc 10 to 15 601.92 588.78 583.78 3.14 D-2[) 27.0 598.65 i pvc 22 to 27 60147 576.65 571.65 2.82 0-3 15.0 599.00 i pvc to to 15 602.48 589.00 584.00 3.48 D-3E) 27.0 598.91 1 pvc 22 to 27 602.22 576.91 971.91 3.31 0-4 15.0 598.48 1 pvc 10 to 15 602.55 588.48 583.48 4.07 0-5 15.0 59858 1 pvc 10 to 15 602.27 588.58 583.58 3.69 S-i 14.5 594.99 i pvc 95 to 14.5 595.60 58549 580.49 0.6!

S-ID 28.0 1 pvc 23 to28 * * *

• 5-2 14.5 592.72 1 pvc 9,5 to 14.5 593.32 583.22 578.22 0.60 5-21) 23.5 592.72 1 ~vc 18.5 to 23.5 593.98 574.22 569.22 1.26 5-3 14.5 592.65 1 pvc 9,5 to 14.5 593.37 583.15 578.15 0.72 5-4 14.5 594.23 i pvc 9~5to 14.5 594.63 584.73 579.73 0.40 S-4D 24.5 i pvc 19.5 to 24.5 * * *

• 5-5 14.5 592.76 1 Pvc 9.5 to 14.5 59344 583.26 578.26 0.68 5-6 14.5 594.99 i pvc 9,5 to 14.5 595.57 585.49 58049 0.58 5-7 13.6

• i pvc 86to1336 * * *

• 5-71) 27.5

• i pvc 22.5 to 27.5 * * *

• c-I 14.5 59070 i pvc 9~5to 14.5 595.35 551.20 576.20 4.65 (3-2 14.5 59024 i pvc 9,5 to 14.5 590.82 580.74 575.74 0.38 G-2D 24.0 i pvc 19to24 * * *

• 0-3 14.5 592 34 pvc 9,5 to 14.5 592.93 582.84 577.84 0.59 F-i 14.0 59527 i pvc 9 to 14 59625 586.27 581.27 0.98 F-iD 24.0 59527 I pvc I9 to 24 596.19 576.27 571.27 0.92 CRA 30841 Presentalion 3TI

DRAFT Page 6 of 6 TABLE I MONITORING WELL CONSTRUCTION SPECIFICATIONS EXELON GENERATION BRAIDWOOD STATION Well Boring Ground Well Well Screen Top ofRiser Screen Top Screen Bottom Stick Number Total Depth Surface Diameter Material Interval Elevation Elevation Elevation Up 2

(ft B(S) (NOW)) (inches) (ftBGS) (NOV13) (NOV17) (NOV17) (ftAGS)

F-2D 25.0 594.05 I pvc 20 to 25 597.26 574.05 569.05 3.21 F-3D 25.0 594.59 1 ~vc 20 to 25 597.36 544.59 539.59 2.77 F-41) 295

• i pvc 24 Sto 295 * * *

• F-Sf) 270

• i pvc 22to27 * * *

• F-6D 275

• i pvc 225to275 * * *

• 7 F-7D 280

• I pvc 3to28 * *

• a-F-SD 26.0

• i pvc 21 to 26 * * *

• c-i 14.0 595.00 1 pvc 9 to 14 595.78 586.00 581.00 0.78 c-ID 24.0 595.00 1 pvc 19 to 24 595.87 576.00 571.00 (1.87 15.5 1 pvc io.s to 15.5 * * *

• c-21) 27.5 -! pvc 22.5 to 27.5 A-I 15.0 I pvc io to is A-iD 25.0 i pvc 20to25 Notes ft SOS feet below ground surface NGvD - National Geodetic vertical Datum pvc - polyvinyl chloride above ground surface Abandoned ground surface not yet shot, survey data incomplete IRA 10841 Pnsentation 3- TI

DRAFT Page 1 of 4 TABLE 2

SUMMARY

OF TRITIUM RESULTS IN MONITORING WELLS EXELON GENERATION BRAID WOOD STATION Location Sample Name Sample Date 3H-Tritium (pCiIL)

A-I GWOI I 106-MB-A-i 1/11/2006 33 A-ID GWOII1O6-MB-A-ID 1/11/2006 60 BL-Ol GW-l I 1705-JK-BL-01 II / 17/ 2005 70 BL-02 c;w-i i 1705-JK-BL-02 11 / 17/2005 156 BL-03 GW-111805-JK-BL-15 11/18/2005 0 BL-04 GW-1 11805-JK-BL-14 11/18/2005 40 BL-05 GW-111805-JK-BL-13 11/18/2005 102 BL-06 GW-I1 1805-JK-BL-12 11/18/2005 114 BL-07 GW-111805-JK-BL-11 11/18/2005 39 BL-08 GW-111805-JK-BL-10 11/18/2005 90 BL-09 c;w-o125o6-JL-BL-9 1/25/2006 4809 BL-09D GW-012506-JL-BL-9D 1/25/2006 20383 BL-10 GW-010406-JL-BL-10 1/4/2006 -104 BL-IOD GW-010406-JL-BL-IOD 1/4/2006 7535 BL-11 GW-01O30&-JL~BL-11 1/3/2006 13 BL-IID GW-010306-JL-BL-IID 1/3/2006 -27 BL-12 GW~010306JirBL12 1/3/2006 39 BL-12D GW-010306-JL-BL-12D 1/3/2006 -35 BL-1 3 c;w-oIo3o6-J L-BL-13 1/3/2006 -16 BL-1 3D Gw-010306-JL-BL- 13D 1/3/2006 9 BL-14 GW-010306-JL-BL-14 1/3/2006 -37 BL-14D GW-010306-JL-BL-14D 1/3/2006 -91 BLI5 GW010306JLBIr15 1/3/2006 146 BL-15D GW-010306-JL-BL-15D 1/3/2006 -49 BL-16 GW-010306-JL-BL-16 1/3/2006 3364 BL-16D GWMIO3O&JLBLrI6D 1/3/2006 91 13L-17 GW-010306-)L-BL-17 1/3/2006 -44 BL-17D GW-010306-JL-BL-17D 1/3/2006 -126 BL-18 GW-120105-DS-BL-18 12/1/2005 108 BL-19 GW-120105-DS-BL-19 12/1 /2005 37 LIL-20D GW-0I0406-J1rBL-20D 1/4/2006 -117 Cl GW-010306-JL-C-i 1/3/2006 -80 C-iD GW-0I0306-JL-C-ID 1/3/2006 -140 C-2 GW-012406-MB-C-2 1/24/2006 -48 C-2D GW-012406-MB-C-2D 1/24/2006 147 D-I GW-010406-JL-D-1 1/4/2006 -13 D-ID GW-010406-JL-D-ID 1/4/2006 -141 D-2 cw-010406-JL-D-2 1/4/2006 -165 D-2D GW-010406-JL-D-2D 1/1/2006 -36 D-3 GW-010406-JL-D-3 1/4/2006 -168 D-3D GW-010406-JL-D-3D 1/4/2006 5110 D-4 GW-120605-JRB-D-4 12/6/2005 91 1)-s GW-120205-MK-D-5 12/2/2005 73 Ditch at Culvert Ditch at Culvert12/22/05 12/22/2005 1007 Ditch by Alpha Gate Ditch by Alpha Gate01/12/06 1/12/2006 -30 F-I GW-010306-JL-F-1 1/3/2006 -44 F-ID GW-010306-JL-F-i 1) 1/3/2006 -56 CRA IVreseFlta

DRAFT Page 2 of 4 TABLE 2

SUMMARY

OF TRITIUM RESULTS IN MONITORING WELLS EXELON GENERATION BRAIDWOOD STATION Location Sample Name Sample Date 311-Tritium (pCi/L)

F-2D GW-0l 1206-MB-F-2D 1/12/2006 546 F-3D GW-01 1206-MB-F-3D I / 12/2006 1689 F-4D GW-012406-MB-F-4D 1/24/2006 -22 F-SD GW-012406-MB-F-5D 1/24/2006 1512 F-6D GW-012406-MB-F-6D 1/24/2006 689 F-7D GW-012406-MB-F-7D 1/24/2006 575 F-8D GW-0124o6-MB-F-8D 1/24/2006 872 G-i GW-120605-JL-G-1 12/6/2005 133 G-2 GW-120605-JL-G-2 12/6/2005 87 G-3 GW-120605-jL-G-3 12/6/2005 81 MW-101 GW-i11505-JK-17-Dup 11/15/2005 162 MW-l01 GW-11i505-JK-17 11/15/2005 157 MW-102 MW-102 3/24/2005 58 MW-103 GW-1i{505-JK-i3-Dup 11/15/2005 1970 MW-103 GW-111505-JK-13 11/15/2005 2497 MW-104 MW-104 7/28/2005 142 MW-lOS GW-010406-JL-MW-105 1/4/2006 169 MW-105D GW-010406-JL-MW-105D 1/4/2006 -120 MW-106 GW-010406-IL-MW-106 1/4/2006 -35 MW-106D GW-010406-JL-MW-iO6D 1/4/2006 -25 MW-107 GW-111605-JK-19 11/13/2005 269 MW-lOS GW-111605-JK-20 11/15/2005 91 MW-109 GW-093005-DC-03 9/30/2005 305 MW-lb GW-010406-JK-MWIIO 1/4/2006 -104 MW-Ill GW-010406-JL-MW-i11 1/4/2006 -78 MW-I 111) GW010906-MB-MW111D 1/9/2006 -66 MW-112 GW-010406-JL-MW-112 1/4/2006 -127 MW-I 12D GWOIO9O6-MB-MWI12D 1/9/2006 -111 MW-I 13 GW-010306-JL-MW-113 1/3/2006 4008 MW-113D GW-0b0306-JL-MW-113D 1/3/2006 4772 P-I GW-120105-DS-P-i 12/1/2005 2484 P-ID GW-I20605jL~PI0 12/6/2003 1723 P-Il GW-120605-JL-P-1I 12/6/2005 1476 P-12 GW-120605-JL-P-12 1276/2005 1622 P-13D GW-012506-JL-P-13D 1/25/2006 217122 P44 GW-0l 2406-MB-P-i 4 1/24/2006 2537 P-i4D GW-012406-MB-P-14D 1/24/2006 2388 P-2 GW-010306-JL-P-2 1/3/2006 2045 P-2D GW-010306-JL-P-21) 1/3/2006 2384 P-3 Gw-12o2o5-MK-P-3 12/2/2005 3238 GW-012506-JLrP-4 1/25/2006 9588 p.41) GW-012506-JL-P-4D 1/25/2006 38965 P-S c;w-obo3o6-JL-P-s 1/3/2006 6166 P-3D GW-010306-JL-P-SD 1/3/2006 2165 P-6 GW-01 1806-MB-P-6 1/18/2006 11(1 P-7 GW-120105-DS-P-7 12/1/2005 1210 P-8 GW-120605-JL-P-8 12/6/2005 2212 CRA U,S4~Presetac~o3

DRAFT Page 3 of 4 TABLE 2

SUMMARY

OF TRITIUM RESULTS IN MONITORING WELLS EXELON GENERATION BRAIDWOOD STATION Location Sample Name Sample Date 3H-Tritium (pCi/LI P-9 GW-121305-JL-P-9-recount 12/13/2003 27 P-9 CW-121305-JL-P-9 12/13/2005 III PW-6P Pond-~I2/08/05 12/8/2005 142 RW-1 RW-l-12/04/05 12/4/2005 7855 RW-2 GW-1213O5-JL-RW2@20 12/13/2005 171166 RW-2 CW-121305-JL-RW2@25 12/13/2005 246442 RW-2 GW-12b305-JL-RW2@I0 12/13/2005 54111 RW-3 GW-b 20205-JL-RW-3 12/2/2003 197 RW-4 GW-120205-JL-RW-4 12/2/2005 380 S-I GW-120605-JL-S-1 12/6/2005 83 5-2 GW-0i0306-JL-S-2 1/3/2006 62 S-2D CW-010306-JL-S-2D 1/3/2006 -2 5-3 GW-I 20605-JL-S-3 12/6/2005 57 5-4 GW-120605-JL-S-4 12/6/2005 1086 5-5 CW-120605-JL-5-5 12/6/2005 1874 5-6 GW- 120605-JL-S-6 12/6/2005 411 5-7 CW-012406-MB-S-7 1/24/2006 1373 5-71) GW-012406-MB-S-7D 1/24/2006 1546 SC-I SC-I 7/28/2005 61.3 SC-2 SC-2 7/28/2005 1970 SG-3 SG-3 7/28/2005 -21.4 SW-I Lake#111/30/05 11/30/2005 2464 SW-2 CW-012506-JL-SW-2 1/25/2006 2441 SW-3 GW-120205-NW-FTL-Lake 12/2/2005 96 SW-4 GW-1202O5-SE-FTL- Lake 12/2/2005 83 YB-I YB-I -05/27/2005 5/27/2005 51295 YB-I-i GW-010406-JL-VBI-l 1/4/2006 425 VB-l-ID GW-010406-JL-VBI -ID 1/4/2006 -132 VB-1-2 GW-I II 705-JK-VBI-2 11/17/2005 337 VB-I-2D GW-011306-MB-YBI-2D 1/13/2006 238 VB-l-3 GW-I 1 1605-DC-YBI-3 lb / 15/2005 206 VB-l-3D c;w-0n3o6-MB-v31-3D 1/13/2006 1943i YB-I-4 GW-111605-DC-VBI-4 11/15/2005 384 YB-1-4D CW-011306-MB-VB1-4D 1/13/2006 7424 YB-I-S GW-111605-DC-YB1-5 11/15/2003 130 YB-i-SD c;W-oII3o6-JL-vBl-SD 1/13/2006 22928 VB-I-6 c;W-iI22os-JL-YBI-6 11/22/2005 93 YB-I-6D GW-0i1306-JL-YB1-6D 1/13/2006 41 YB-I-7 CW-i 12205-JL-VBI-7 11/22/2005 140 YB-4-7D GWOIO9O6-MB-YBI-7D 1/9/2006 -116 YB-I-S CW-I 12205-JL-YBI-8 11/22/2005 57 YB-i -SD GW010906-MB-YBI-8D 1/9/2006 10877 YB-i-9 GW-1 12205-JL-YBI-9 11/22/2005 107 YB-l-9D GW-011306-MB-YBI-9D 1/13/2006 3370 YB-2-i CW-111505-DC-YB2-1-Dup 11/15/2005 2.38 Y13-2-2 CW-0i0406-JL-VB2-2 1/4/2006 5232 YB-2-2D CW-010406-JL-YB2-2D 1/4/2006 4037 CRA I6S4~ Pre~erit12~n 2-12

DRAFT Page 4 of 4 TABLE 2

SUMMARY

OF TRITIUM RESULTS IN MONITORING WELLS EXELON GENERATION BRAID WOOD STATION Location Sample Name Sample Date 3H-Tritiun (pCi/L)

YB-2-3 GW-I 1 1505-DC-YB2-3-Dup 11/15/2005 3460 YB-2-3 GW-I I1505-DC-YB2-3 11 / 15/2005 3940 YB-2-4 CW-1 I 1505-DC-YB2-4-Dup 11/15/2005 3350 YB-2-4 CW-111505-DC-YB2-4 11/15/2005 3664 YB-2-5 CW-010306-JL-YB2-5 1/3/2006 3834 YB-2-SD GW-010306-JL-YB2-SD 1/3/2006 102 YB-2-6 CW-010306-JL-YB-2-6 1/3/2006 1412 YB-2-6D CW-010306-JL-YB-2-6D 1/3/2006 44 YB-2-7 c;W-oio4oó-L-YB2-7 1/4/2006 -60 YB-2-7D GW-010406-JL-YB2-7D 1/4/2006 -53 YB-2-8 CW-121405-JS-YB-2-8 12/14/2005 -103 YB-2-9 GW-011206-MB-YB2-9 1/12/2006 78 YB-2-9D CW-0I 1206-MB-YB2-9D 1/12/2006 -65 YB-3 YB-3--05/11/2005 5/11/2005 1521 YB-3-I CW-1II505-DC-YB3-1 11/15/2005 5959 YB-3-I GW-I I 1505-DC-YB3-I-Dup 11/15/2005 5460 YB-3-10 CW-010306-JL-YB3-I0 1/3/2006 12076 YB-3-I OD GW-010306-JL-YB3-1OD 1/3/2006 108736 YB-3-2 CW-I I 1505-DC-YB3-2 Ii / 15/2005 32830 YB-3-3 GW-11I605-DC-YB3-3 11/16/2005 43894 YB-3-4 CW-010306-JL-YB3-4 1/3/2006 29286 YB-3-4D CW-010306-JL-YB3-4D 1/3/2006 790 YB-3-5 GW-I 12205-JL-YB3-5 11/22/2005 95 YB-3-6 GW-I 12205-JL-YB3-6 11/22/2005 33372 YB-3-7 CW-010306-JL-YB3-7 1/3/2006 -126 YB-3-7D GW-010306-JL-YB3-7D 1/3/2006 -205 YB-3-8 GW- 1 20205-MK-YB-3-8 12/2/2005 171 YB-3-9D CW-010406-JL-YB3-9D 1/4/2006 19605 CRA l(~S-~!

f>re~cn~a

DRAFT Page 1 of 1 TABLE 3

SUMMARY

OF TRITIUM RESULTS AT PRIVATE WELLS EXELON GENERATION BRAIDWOOD STATiON Location Sample Date 311-Tritium (pCi/U PW-1 11/30/2005 -26 PW-2 11/30/2005 48 PW-3 11/30/2005 25 PW-4 12/2/2005 43 PW-5 1/19/2006 -12 PW-7 12/7/2005 -58 PW-8 12/8/2005 1367 PW-9 12/5/2005 142 PW-l0 12/7/2005 72 PW-11 12/5/2005 99 PW-12 12/7/2005 44 PW-13 12/7/2005 -62 PW-14 12/14/2005 -118 PW-15 12/14/2005 -51 CRA (14] resen th In $ -

APPENDIX B FIELD PROCEDURES 016841 (12)

1.0 SITE-SPECIFIC SAMPLING PLAN This appendix provides a discussion of the methods used to perform field activities at the Braidwood Station during the investigation of tritium in groundwater.

1.1 PERMANENT MONITORING WELL INSTALLATION Installation procedures for the permanent monitoring wells are outlined below:

i) Monitoring wells were installed using 41/4-inch inside diameter hollow stem augers.

ii) Upon reaching the target depth, a 10-foot length of No. 10 slot, 2-inch diameter polyvinyl chloride (PVC) well screen and sufficient PVC riser pipe to extend above the ground was installed in the borehole; iii) A filter sand pack consisting of silica sand was inserted to a general height of 1 to 2 feet above the well screen; and iv) The short length of borehole annulus remaining above the sand pack was sealed using 3/8-inch diameter bentonite chips.

The permanent wells were fitted with a protective casing and locking cap.

1.2 PERMANENT MONITORING WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the permanent wells were developed. Well development was conducted in accordance with the procedures outlined below:

i) Water was purged from the well using a peristaltic pump and dedicated tubing.

ii) Groundwater was collected at regular intervals and the pH, temperature, and conductivity were measured using field instruments. These instruments were calibrated daily according to the manufacturer's specifications. Additionally, observations such as color, odor, and turbidity of the purged water were recorded.

iii) Development continued until the turbidity of the monitoring wells was significantly reduced and three consistent readings of pH, temperature, and 016841 (12) B-1 CONESTOGA-ROVERS & ASSOCIATES

conductivity were recorded, or a minimum of ten well volumes were purged.

1.3 TEMPORARY MONITORING WELL INSTALLATION Shallow and deep temporary monitoring wells were installed using direct push (Geoprobe) methods. Shallow wells range in depth from 11 to 21 feet bgs. Deep wells range in depth from 21 to 41 feet bgs. Deep wells were installed to the top of the underlying clay layer, the location of which was determined at each location in one of two ways. The top of the clay layer was identified by using a Geoprobe macrocore and visually looking at the soil sample retrieved in the macrocore or identified by a noticeable change in resistance encountered by the Geoprobe and noted by the Geoprobe operator.

Installation procedures for the temporary monitoring wells are outlined below:

i) Upon reaching the target depth, a 5-foot length of No. 10 slot, 1-inch diameter PVC well screen and sufficient PVC riser pipe to extend above the ground surface was installed in the borehole; ii) A filter sand pack consisting of silica sand was inserted to a general height of 1 to 2 feet above the well screen; iii) Under certain drilling conditions, approximately 2 gallons of water was added to the borehole to keep sand from coming into the boreholes; 1and iv) the short length of borehole annulus remaining above the sand pack was sealed using 3/8-inch diameter bentonite chips.

The temporary wells were fitted with watertight caps.

1.4 TEMPORARY MONITORING WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the temporary wells were developed. Well development was conducted in accordance with the procedures outlined below:

1 Heaving sands were often encountered during drilling and installation of the temporary wells.

In order to compensate for the upflow of sand into the Geoprobe core, clean water was added to create a downward head during the installation of the PVC casing.

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i) Water was purged from the well using a peristaltic pump and dedicated tubing. Two gallons of water was added during well installation; therefore, two times that amount of water needed to be purged to ensure groundwater samples would be representative of the underlying groundwater.

ii) Groundwater was collected at regular intervals and the pH, temperature, and conductivity were measured using field instruments. These instruments were calibrated daily according to the manufacturer's specifications. Additionally, observations such as color, odor, and turbidity of the purged water were recorded.

iii) Development continued until the turbidity and silt content of the monitoring wells were significantly reduced and three consistent readings of pH, temperature, and conductivity were recorded, or a minimum of ten well volumes were purged.

1.5 INSTALLATION OF RECOVERY WELLS The recovery wells were advanced to reach the top of the underlying clay layer, between 24 to 28 feet bgs.

Installation procedures for the recovery wells are outlined below:

i) Recovery wells were installed using 61/4-inch inside diameter hollow stem augers.

ii) Upon reaching the target depth, a 20 foot length of No. 10 slot, 4 inch diameter PVC well screen and sufficient PVC riser pipe to extend to the ground was installed in the borehole; iii) A filter sand pack consisting of silica sand was inserted to a general height of 1 to 2 feet above the well screen; and iv) The short length of borehole annulus remaining above the sand pack was sealed using 3/8-inch diameter bentonite chips.

The recovery wells were fitted with watertight caps and locking caps. All soil cuttings were containerized into 55-gallon drums, sealed, labeled, and retained on Site.

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1.6 RECOVERY WELL DEVELOPMENT In order to establish good hydraulic communication with the aquifer and reduce the volume of sediment in the wells, the recovery wells were developed. Well development was conducted in accordance with the procedures outlined below:

i) Water was purged from the well using a disposable bailer; and ii) Two well volumes where removed from the well.

1.7 GROUNDWATER AND SURFACE WATER LEVEL MEASUREMENTS The depth to water in each well was measured to the nearest 0.01 foot using an electronic water level meter that was cleaned prior to use at each well. To minimize sample turbidity, the water level meter probe was lowered slowly when measuring the total depth of the well. Measurements were recorded after each well installation and at each sampling event. Surface water level measurements were recorded by reading the staff gauges.

1.8 GROUNDWATER SAMPLING AND ANALYSES Groundwater samples were collected from permanent, temporary, and recovery wells. Groundwater samples collected for tritium analyses were delivered to an Exelon representative, who submitted them to Environmental, Inc. of Northbrook, Illinois, to the Illinois Emergency Management Agency (IEMA), and to the NRC for analyses. Groundwater samples collected for total metals, general chemistry, groundwater quality, sodium, and chloride analyses were hand delivered to First Environmental Laboratories, Inc. (First Environmental) of Naperville, Illinois.

1.8.1 CRA GROUNDWATER SAMPLING PROTOCOLS Groundwater samples were collected in accordance with the CRA Slow Purging/Minimal Disturbance Protocols specified below.

i) A new pair of disposable latex gloves was used for each sample.

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ii) The depth to water in each well was measured to the nearest 0.01 foot using an electronic water level meter. In order to minimize sample turbidity, the probe of the water level meter was lowered slowly to measure the total depth of the well.

iii) Prior to sampling, each well was purged using a peristaltic pump. New tubing was used at each well. The well was purged at a low rate to minimize draw down and sediment agitation.

iv) Permanent and temporary monitoring wells were purged by time intervals.

v) Field measurements of temperature, pH, conductivity, and turbidity of the purged water were obtained and recorded in three time intervals.

vi) After purging for 13 to 20 minutes, water samples were collected using the peristaltic pump. Containers were rinsed three times and filled after the third time of rinsing.

vii) Recovery wells were sampled by using a disposable bailer. Two well volumes were removed prior to sample collection.

The title page of each logbook contained the following information:

• person to whom the logbook is assigned;

• logbook number;

• project name;

• project start date; and

• end date.

Entries into the logbook contained a variety of information. At the beginning of each day's logbook entry, the date, start time, weather conditions, and the names of all sampling team members present were entered. The names of individuals visiting the Site or field sampling team and the purpose of their visit were also recorded in the field logbook.

All field measurements obtained and samples collected were recorded. All logbook entries were made in ink, signed, and dated with no erasures. If an incorrect logbook entry was made, the incorrect information was crossed out with a single strike mark that was initialed and dated by the person making the erroneous entry. The correct information was entered into the logbook adjacent to the original entry.

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Whenever a sample was collected or a measurement is made, a detailed description of the location was recorded in the logbook. Photographs taken at a location, if any, were noted in the logbook. All equipment used to obtain field measurements was recorded in the field logbook. In addition, the calibration data for all field measurement equipment was recorded in the field logbook or on the appropriate Field Data Record Form.

The equipment used to collect samples, time of sample collection, sample description, volume and number of containers, and preservatives added (if applicable) were recorded in the field logbook. Each sample was uniquely identified using the sample numbering system developed for this Site.

The following packaging and shipping procedures were used to ensure that the chain-of-custody of samples collected for chemical analysis remains intact:

1. The field sampler is personally responsible for the care and custody of the samples until they are transferred to another person or the laboratory. As few people as possible will handle the samples.

2. All sample containers will be identified by using sample labels that include the unique sample identification number and the date and time of collection. Sample labels will be completed for each sample using waterproof ink.

3. A properly completed chain-of-custody form will accompany samples. The sample identification numbers and required analyses will be listed on the chain-of-custody form. When transferring the possession of samples, the individuals relinquishing and receiving the samples will sign and record the date and time on the form. The chain-of-custody form documents sample custody transfers from the sampler to another person, to the laboratory, or to/from a secure storage area.

4. Samples will be properly packaged for shipment and dispatched to the laboratory for analysis with a separate signed chain-of-custody form enclosed in each shipping cooler. Shipping coolers will be secured with custody tape for shipment to the laboratory. The custody tape will be covered with clear plastic tape to prevent accidental damage to the custody tape.

5. If samples are collocated (split) with a government agency or other entity, it is the responsibility of that entity to prepare its own chain-of-custody form for the samples. Information regarding the identity of the entity and the samples that are being collocated will be recorded in the field logbook.

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6. The chain-of-custody form identifying its contents will accompany all sample shipments. The chain-of-custody form is a four-part carbonless-copy form. The form is completed by the sampling team, which, after signing and relinquishing custody to the shipper, retains the bottom (goldenrod) copy. The shipper, if different than the sampling team members, retains the pink copy after relinquishing custody to the laboratory. The yellow copy is retained by the laboratory and the fully executed white copy is returned as part of the data deliverables package.

7. If the samples are sent by common carrier, a bill of lading (e.g., FedEx airbill) will be used and copies will be retained as permanent documentation. Commercial carriers are not required to sign the chain-of-custody form as long as the form is sealed inside the sample cooler and the custody tape remains intact.

The above procedures were further expanded to address the requirements of Exelon, Environmental, Inc., and Site conditions. These are presented below.

1.8.2 EXELON GROUNDWATER SAMPLING PROTOCOLS In addition to the above CRA standard protocols, the procedures were supplemented with Exelons protocols as specified below.

1) Sampler shall start with clean empty bottles.

2) Purge the well to stabilize the pH, conductivity, and temperature.

3) Label the sample bottles with the location and date.

4) Obtain a peer check on the label, location, well #, etc., for the first bottle filled at each well.

5) Rinse the bottles 3 times.

6) Fill at least three (3) bottles for each sample.

7) Log each sample and number of containers on the 4-part Chain of Custody form.

8) The sampler relinquishes all sample containers to an Exelon employee and signs/dates the 4-part Chain of Custody form as RELINQUISHED BY.

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9) The Exelon employee receives all sample containers and signs/dates the 4-part Chain of Custody form as RECEIVED BY.

10) The sampler retains the Shipper Copy (Pink) and the Sampler Copy (Goldenrod) of the 4-part Chain of Custody form.

11) The Exelon employee retains the Fully Executed Copy (White) and the Receiving Laboratory Copy (Yellow) of the 4-Part Chain of Custody form.

12) The Exelon employee relinquishes at least 1 container of each sample to the Environmental Inc. representative and signs/dates the 4-part Chain of Custody form as RELINQUISHED BY. The Exelon employee shall note in the remarks column the number of containers of each sample relinquished.

13) The Environmental Inc. representative receives the sample containers and signs/dates the 4-part Chain of Custody form as RECEIVED BY.

14) The Environmental Inc. representative retains the Receiving Laboratory Copy (Yellow) of the 4-part Chain of Custody form.

15) The Exelon employee retains the Fully Executed Copy (White) of the 4-Part Chain of Custody form.

16) The Environmental Inc. representative delivers the sample(s) to Environmental Inc. Midwest Lab.

17) The Exelon employee relinquishes all sample containers to the Exelon Tritium Team clerk and signs/dates the 4-part Chain of Custody form as RELINQUISHED BY.

18) The Exelon Tritium Team clerk receives the sample containers and signs/dates the 4-part Chain of Custody form as RECEIVED BY.

19) The Exelon Tritium Team clerk retains the Fully Executed Copy (White) of the 4-Part Chain of Custody form.

20) The Exelon Tritium Team clerk shall place one container of each sample in a locked file cabinet drawer labeled SAMPLES FOR NRC.

21) The Exelon Tritium Team clerk shall place one container of each sample in a locked file cabinet drawer labeled SAMPLES FOR IEMA.

22) When requested by the NRC, the Exelon Tritium Team clerk shall relinquish containers from the drawer labeled SAMPLES FOR NRC 016841 (12) B-8 CONESTOGA-ROVERS & ASSOCIATES

and sign a suitable Chain of Custody form provided by the NRC identifying the samples relinquished.

23) The NRC representative shall receive the containers from the drawer labeled SAMPLES FOR NRC and sign the applicable Chain of Custody form.

24) The Exelon Tritium Team clerk shall retain a copy of the signed Chain of Custody form provided by the NRC.

25) When requested by the IEMA, the Exelon Tritium Team clerk shall relinquish containers from the drawer labeled SAMPLES FOR IEMA and sign a suitable Chain of Custody form provided by the IEMA identifying the samples relinquished.

26) The IEMA representative shall receive the containers from the drawer labeled SAMPLES FOR IEMA and sign the applicable Chain of Custody form.

27) The Exelon Tritium Team clerk shall retain a copy of the signed Chain of Custody form provided by the IEMA.

28) The Exelon Tritium Team clerk shall maintain a log (hardcopy and/or electronic) of all samples placed in the locked cabinets. As a minimum, for each sample the log shall identify:

a) Sample ID b) Sample Date c) Date sample was placed in NRC cabinet d) Date sample was place in IEMA cabinet e) Date sample was relinquished to the NRC representative and the NRC representative's name f) Date sample was relinquished to the IEMA representative and IEMA representatives name 1.9 SURFACE WATER SAMPLING Surface water samples were collected as grab samples. Sample bottles were placed into the pond, rinsed three times, and filled half way. The samples were 016841 (12) B-9 CONESTOGA-ROVERS & ASSOCIATES

delivered to an Exelon representative, who shipped them to Environmental, Inc.

and the IEMA for chemical analysis of tritium.

1.10 PRIVATE WATER WELL SAMPLING PROGRAMS Exelon initiated sampling of nearby private wells in November 2005. This routine private well sampling program is for 15 locations (residences) found north of Smiley Road and downgradient of the impacted groundwater areas.

The following describes the procedures listed to sample the 15 wells presented on Figure 2.2.

A letter from CRA explaining the voluntary private well residential sampling program was hand delivered to the nearby Braidwood residents by Exelon.

Residents were requested to sign an access agreement to allow CRA onto their property to sample their well. Once access was granted, sampling was conducted. Water samples were collected from an outside, unsoftened faucet, if available. If an outside faucet was not available the sample was collected from inside the residents home. Before collecting a water sample the faucet was run for 15 minutes. After 15 minutes, three 500-milliliter bottles were each rinsed three times each and then filled to the top. The bottles were delivered daily to an Exelon representative, who shipped one bottle to Environmental, Inc., one bottle to the IEMA, and one bottle to the NRC for independent testing. Once results were obtained, a copy of the final laboratory reports was provided to the resident along with an explanation of the test results.

1.11 SINGLE WELL AQUIFER TESTING Single well hydraulic response tests were performed using rising head methods, wherein the water level in a monitoring well is depressed and water level recovery is monitored over time. A pressure transducer and data logger monitored water levels. Data obtained from the single well response tests was evaluated using the methods developed by Bouwer & Rice (1976).

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APPENDIX C MONITORING WELL STRATIGRAPHIC AND INSTRUMENTATION LOGS 016841 (12)