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to Hydrogeologic Investigation Report, Fleetwide Assessment for Byron Generating Station.
	ML062750384
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Site:	Byron
Issue date:	09/30/2006
From:	; Conestoga-Rovers & Associates
To:	; Exelon Generation Co, Office of Nuclear Reactor Regulation
References
	045136 (13), FOIA/PA-2010-0209
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Revision 1 Certain figures in this Report contain sensitive, security-related information protected from public disclosure by Federal and State law. This Report is suitable for public disclosure only after these figures are removed.

HYDROGEOLOGIC INVESTIGATION REPORT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Prepared For:

Exelon Generation Company, LLC DISCLAIMER: Prepared by:

SOME FORMATTING CHANGES MAY HAVE OCCURRED WHEN THE ORIGINAL DOCUMENT WAS PRINTED TO PDF; HOWEVER, Conestoga-Rovers THE ORIGINAL CONTENT REMAINS UNCHANGED. & Associates 651 Colby Drive Waterloo, Ontario Canada N2V 1C2 Office: (519) 884-0510 Fax: (519) 884-0525 SEPTEMBER 2006 web: http:\\www.CRAworld.com REF. NO. 045136 (13)

Worldwide Engineering, Environmental, Construction, and IT Services

Revision 1 TABLE OF CONTENTS Page EXECUTIVE

SUMMARY

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

1.0 INTRODUCTION

...................................................................................................................1 2.0 STATION DESCRIPTION .....................................................................................................2 2.1 STATION LOCATION .......................................................................................2 2.2 OVERVIEW OF COOLING WATER OPERATIONS.....................................2 2.3 SURROUNDING LAND USE ...........................................................................3 2.4 STATION SETTING............................................................................................4 2.4.1 TOPOGRAPHY AND SURFACE WATER FEATURES.................................4 2.4.2 GEOLOGY ............................................................................................................5 2.4.3 HYDROGEOLOGY .............................................................................................7 2.4.3.1 EXISTING WELL NETWORK ...........................................................................8 2.4.3.2 GROUNDWATER FLOW ..................................................................................9 2.5 AREA GROUNDWATER USE ..........................................................................9 3.0 AREAS FOR FURTHER EVALUATION...........................................................................11 3.1 SYSTEMS EVALUATIONS..............................................................................11 3.2 HISTORICAL RELEASES ................................................................................14 3.3 STATION INVESTIGATIONS.........................................................................14 3.3.1 PRE-OPERATIONAL RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM .......................................14 3.3.2 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM .........................................................................................................15 3.3.3 HISTORIC INVESTIGATIONS .......................................................................15 3.3.3.1 POWER PLANT DOCUMENTS - UFSAR REPORT ....................................15 3.3.3.2 BLOWDOWN LINE INVESTIGATION.........................................................15 3.4 IDENTIFIED AREAS FOR FURTHER EVALUATION ...............................16 4.0 FIELD METHODS.................................................................................................................19 4.1 BLOWDOWN LINE INVESTIGATION ACTIVITIES .................................19 4.1.1 GROUNDWATER MONITORING WELL INSTALLATION.....................19 4.1.2 GROUNDWATER MONITORING WELL DEVELOPMENT ....................21 4.1.3 SURVEY ..............................................................................................................22 4.1.4 GROUNDWATER ELEVATION MEASUREMENTS..................................22 4.1.5 GROUNDWATER SAMPLE COLLECTION ................................................22 4.2 FLEETWIDE INVESTIGATION ACTIVITIES...............................................23 4.2.1 GROUNDWATER ELEVATION MEASUREMENTS..................................23 4.2.2 GROUNDWATER SAMPLE COLLECTION ................................................24 4.2.3 DATA QUALITY OBJECTIVES.......................................................................26 4.2.4 SAMPLE IDENTIFICATION ...........................................................................26 4.2.5 CHAIN-OF-CUSTODY RECORD...................................................................27 045136 (13) Byron Generating Station CONESTOGA-ROVERS & ASSOCIATES

Revision 1 TABLE OF CONTENTS Page 4.2.6 QUALITY CONTROL SAMPLES ...................................................................27 4.2.7 ANALYSES.........................................................................................................28 5.0 RESULTS

SUMMARY

..........................................................................................................29 5.1 STATION GEOLOGY .......................................................................................29 5.2 STATION HYDROGEOLOGY ........................................................................29 5.2.1 GROUNDWATER FLOW DIRECTIONS ......................................................30 5.2.2 MAN-MADE INFLUENCES ON GROUNDWATER FLOW .....................31 5.2.3 VERTICAL HYDRAULIC GRADIENTS........................................................31 5.2.4 LATERAL GROUNDWATER FLOW AND VELOCITY.............................32 5.3 GROUNDWATER QUALITY..........................................................................33 5.3.1

SUMMARY

OF BETA-EMITTING RADIONUCLIDES ANALYTICAL RESULTS.................................................................................34 5.3.1.1 STATION SAMPLING POINTS......................................................................34 5.3.1.2 GROUNDWATER MONITORING WELL SAMPLES.................................34 5.3.1.3 RESIDENTIAL WATER SUPPLY WELLS .....................................................35 5.3.2

SUMMARY

OF GAMMA-EMITTING RADIONUCLIDES ANALYTICAL RESULTS.................................................................................36 5.3.3

SUMMARY

OF FIELD MEASUREMENTS ...................................................36 5.4 SURFACE WATER QUALITY.........................................................................37 6.0 RADIONUCLIDES OF CONCERN AND SOURCE AREAS .........................................38 6.1 GAMMA-EMITTING RADIONUCLIDES.....................................................38 6.2 BETA-EMITTING RADIONUCLIDES ...........................................................38 6.3 TRITIUM.............................................................................................................38 6.3.1 GENERAL CHARACTERISTICS ....................................................................38 6.3.2 DISTRIBUTION IN STATION GROUNDWATER.......................................39 6.3.3 CONCEPTUAL MODEL OF TRITIUM RELEASE AND MIGRATION ...41 7.0 EXPOSURE PATHWAY ASSESSMENT............................................................................43 7.1 HEALTH EFFECTS OF TRITIUM...................................................................43

7.2 BACKGROUND

CONCENTRATIONS OF TRITIUM ................................44 7.2.1 GROUNDWATER.............................................................................................44 7.2.2 PRECIPITATION DATA ..................................................................................44 7.2.3 SURFACE WATER DATA ...............................................................................45 7.2.4 DRINKING WATER DATA ............................................................................46 7.2.5 EXPECTED TRITIUM BACKGROUND FOR THE STATION ...................46 7.3 IDENTIFICATION OF POTENTIAL EXPOSURE PATHWAYS AND POTENTIAL RECEPTORS...............................................................................47 7.3.1 POTENTIAL GROUNDWATER MIGRATION TO DRINKING WATER USERS AT THE STATION PROPERTY .........................................47 7.3.2 POTENTIAL GROUNDWATER MIGRATION TO DRINKING WATER USERS OFF THE STATION PROPERTY .......................................48 045136 (13) Byron Generating Station CONESTOGA-ROVERS & ASSOCIATES

Revision 1 TABLE OF CONTENTS Page 7.3.3 POTENTIAL GROUNDWATER MIGRATION TO SURFACE WATER USERS ..............................................................................48 7.4

SUMMARY

OF POTENTIAL TRITIUM EXPOSURE PATHWAYS.......................................................................................................48 7.5 OTHER RADIONUCLIDES.............................................................................49

8.0 CONCLUSION

S....................................................................................................................50 9.0 RECOMMENDATIONS.......................................................................................................54 9.1 DATA GAPS ......................................................................................................54 9.2 GROUNDWATER MONITORING ................................................................54

10.0 REFERENCES

........................................................................................................................55 045136 (13) Byron Generating Station CONESTOGA-ROVERS & ASSOCIATES

Revision 1 LIST OF FIGURES (Following Text)

FIGURE 1.1 STATION LOCATION MAP FIGURE 1.2 STATION BOUNDARIES AND FEATURES FIGURE 2.1 LOCAL GEOLOGIC CROSS-SECTIONS A-A' AND B-B' FIGURE 2.2 LOCAL GEOLOGIC CROSS-SECTION C-C' FIGURE 2.3 MONITORING WELL LOCATIONS FIGURE 2.4 GROUNDWATER CONTOUR MAP - MARCH 2006 FIGURE 3.1 AREA FOR FURTHER EVALUATION - FORMER FIBERGLASS BLOWDOWN LINE FIGURE 3.2 AREA FOR FURTHER EVALUATION - BLOWDOWN LINE FIGURE 3.3 AREA FOR FURTHER EVALUATION -PROTECTED AREA FIGURE 5.1 HYDROGEOLOGIC CROSS-SECTION LOCATIONS FIGURE 5.2 HYDROGEOLOGIC CROSS-SECTION X1-X1' FIGURE 5.3 HYDROGEOLOGIC CROSS-SECTION X2-X2' FIGURE 5.4 HYDROGEOLOGIC CROSS-SECTIONS X3-X3' AND X3-X3

FIGURE 5.5 POTENTIOMETRIC SURFACE CONTOURS - APRIL 2006 - UPPER GALENA-PLATTEVILLE AQUIFER FIGURE 5.6 POTENTIOMETRIC SURFACE CONTOURS - APRIL 2006 - BOTTOM OF GALENA-PLATTEVILLE AQUIFER FIGURE 5.7 POTENTIOMETRIC SURFACE CONTOURS - APRIL 2006 - ST. PETER SANDSTONE AQUIFER FIGURE 5.8 TRITIUM CONCENTRATIONS - STATION SAMPLING LOCATIONS FIGURE 5.9 TRITIUM CONCENTRATIONS - UPPER GALENA-PLATTEVILLE AQUIFER 045136 (13) Byron Generating Station CONESTOGA-ROVERS & ASSOCIATES

Revision 1 LIST OF FIGURES (Following Text)

FIGURE 5.10 TRITIUM CONCENTRATIONS - BOTTOM OF GALENA-PLATTEVILLE AQUIFER FIGURE 5.11 TRITIUM CONCENTRATIONS - ST. PETER SANDSTONE AQUIFER FIGURE 5.12 TRITIUM CONCENTRATIONS - RESIDENTIAL WELL LOCATIONS FIGURE 5.13 RADIONUCLIDE CONCENTRATIONS 045136 (13) Byron Generating Station CONESTOGA-ROVERS & ASSOCIATES

Revision 1 LIST OF TABLES (Following Text)

TABLE 2.1

SUMMARY

OF EXISTING WELL INFORMATION TABLE 4.1

SUMMARY

OF MONITORING WELL DEVELOPMENT- BLOWDOWN LINE INVESTIGATION TABLE 4.2

SUMMARY

OF GROUNDWATER ELEVATIONS - MARCH/APRIL 2006 TABLE 4.3

SUMMARY

OF MONITORING WELL PURGING PARAMETERS -

MARCH/APRIL 2006 TABLE 4.4 SAMPLE

SUMMARY

- BLOWDOWN LINE INVESTIGATION TABLE 4.5

SUMMARY

OF GROUNDWATER ELEVATIONS - APRIL 24, 2006 TABLE 4.6 SAMPLE

SUMMARY

- FLEETWIDE INVESTIGATION TABLE 4.7

SUMMARY

OF MONITORING WELL PURGING PARAMETERS -

FLEETWIDE SAMPLING EVENT TABLE 5.1 CALCULATED VERTICAL HYDRAULIC GRADIENTS TABLE 5.2

SUMMARY

OF TRITIUM CONCENTRATIONS IN WATER - STATION SAMPLING LOCATIONS TABLE 5.3

SUMMARY

OF TRITIUM CONCENTRATIONS IN GROUNDWATER -

FEBRUARY-APRIL 2006 TABLE 5.4

SUMMARY

OF TRITIUM CONCENTRATIONS IN WATER - RESIDENTIAL WATER SUPPLY WELLS TABLE 5.5

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER 045136 (13) Byron Generating Station CONESTOGA-ROVERS & ASSOCIATES

Revision 1 LIST OF APPENDICES APPENDIX A WATER SUPPLY WELL INFORMATION APPENDIX B MONITORING WELL STRATIGRAPHIC AND INSTRUMENTATION LOGS APPENDIX C QUALITY ASSURANCE PROGRAM C.1 ENVIRONMENTAL, INC.

C.2 TELEDYNE BROWN ENGINEERING, INC.

APPENDIX D LABORATORY ANALYTICAL REPORTS D.1 ENVIRONMENTAL, INC.

D.2 TELEDYNE BROWN ENGINEERING, INC.

APPENDIX E DATA VALIDATION MEMORANDUM 045136 (13) Byron Generating Station CONESTOGA-ROVERS & ASSOCIATES

Revision 1 EXECUTIVE

SUMMARY

This Hydrogeologic Investigation Report (HIR) documents the results of Conestoga-Rovers & Associates' (CRA's) May 2006 Hydrogeologic Investigation Work Plan (Work Plan) pertaining to the Byron Generating Station in Byron, Illinois. CRA prepared this HIR for Exelon as part of its Fleetwide Program to determine whether groundwater at and in the vicinity of its nuclear power generating facilities has been adversely impacted by any releases of radionuclides. This report also documents the results of CRA's and the Byron Station's investigation beginning in January 2006 in relation to the current and former blowdown lines.

CRA collected and analyzed information on historical releases, the structures, components, and areas of the Station that have the potential to release tritium or other radioactive liquids to the environment and past hydrogeologic investigations at the Station. CRA used this information, combined with its understanding of groundwater flow and sample locations at the Station to identify the AFEs for the Station.

CRA collected 39 groundwater samples during the blowdown line investigation and 41 groundwater samples during the fleetwide investigation. CRA also collected two full rounds of water levels from the newly installed and existing wells. The Work Plan was completed in March and April 2006. All groundwater samples were analyzed for tritium, strontium-89/90 and gamma-emitting radionuclides.

The results of the hydrogeologic investigation are:

Gamma-emitting radionuclides associated with licensed plant operations were not detected at concentrations greater than their respective Lower Limits of Detection (LLDs) in any of the groundwater samples obtained and analyzed during the course of this investigation;

Strontium-89/90 was not detected at a concentration greater than the LLD of 2 picoCuries per liter (pCi/L) in any of the groundwater samples obtained and analyzed during the course of this investigation;

Tritium was not detected at concentrations that are greater than the United States Environmental Protection Agency (USEPA) drinking water standard of 20,000 pCi/L;

Low levels of tritium were detected at concentrations greater than the LLD of 200 pCi/L in four out of 39 samples collected, which is considered background, but well below the applicable drinking water standard. These tritium concentrations ranged from 234 +/- 128 pCi/L to 3,260 +/- 367 pCi/L. These four samples were all 045136 (13) Byron Generating Station i CONESTOGA-ROVERS & ASSOCIATES

Revision 1 collected from monitoring wells near three vacuum breaker vaults: VB-2, VB-3, and VB-4. The source of the tritium concentrations in the groundwater was periodic leaks during re-seating of the blowdown line vacuum breaker valves;

Based on the results of this investigation, tritium is not migrating off the Station property at detectable concentrations;

Based on the results of this investigation, there is no current risk from exposure to radionuclides associated with licensed plant operations through any of the identified potential exposure pathways; and

Based on the results of this investigation, there are no known active releases into the groundwater at the Station.

Based upon the information collected to date, CRA recommends that Exelon conduct periodic monitoring of selected sample locations.

045136 (13) Byron Generating Station ii CONESTOGA-ROVERS & ASSOCIATES

Revision 1

1.0 INTRODUCTION

Conestoga-Rovers & Associates (CRA) has prepared this Hydrogeologic Investigation Report (HIR) for Exelon Generation Company, LLC (Exelon) as part of its Fleetwide Program to determine whether groundwater at and in the vicinity of its nuclear power generating facilities has been adversely impacted by any releases of radionuclides. This report documents the results of CRA's May 2006 Hydrogeologic Investigation Work Plan (Work Plan). This investigation pertains to Exelon's Byron Generating Station in Byron, Illinois (Station) (refer to Figure 1.1). This report also documents the results of CRA's and the Station's investigation conducted beginning in January 2006 in relation to the current and former blowdown lines.

The Station is defined as all property, structures, systems, and components owned and operated by Exelon located at 4450 North German Church Road in Byron, Illinois, Rockvale and Marion Townships, Ogle County. The approximate property boundaries are shown on Figure 1.2.

Pursuant to the Work Plan, CRA assessed groundwater quality at the Station in locations designated as Areas for Further Evaluation (AFEs). The process by which CRA identified AFEs is discussed in Section 3.0 of this report.

The objectives of the Work Plan were to:

characterize the geologic and hydrogeologic conditions at the Station, including subsurface soil types, the presence or absence of confining layers, and the direction and rate of groundwater flow;

characterize the groundwater/surface water interaction at the Station, including a determination of the surface water flow regime;

evaluate groundwater quality at the Station, including the vertical and horizontal extent, quantity, concentrations, and potential sources of tritium and other radionuclides in the groundwater, if any;

define the probable sources of any radionuclides released at the Station;

evaluate potential human, ecological, or environmental receptors of any radionuclides that might have been released to the environment; and

evaluate whether interim response activities are warranted.

045136 (13) Byron Generating Station 1 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 2.0 STATION DESCRIPTION The following section presents a general summary of the Station location and definition, overview of Station operations, surrounding land use, and an overview of both regional and Station-specific topography, surface water features, geology, hydrogeology, and groundwater flow conditions. This section also presents an overview of groundwater use in the area.

2.1 STATION LOCATION The Station is located at 4450 North German Church Road in Byron, Illinois, Rockvale and Marion Townships, Ogle County. The Station consists of approximately 1,900 acres, of which approximately 1,200 acres are used for the generating facility. The other approximately 700 acres of property encompass a 'buffer zone' around the facility and property to the west of the facility.

The Byron Station is located approximately 2 miles east of the Rock River. The blowdown line extends from the Station to the Rock River, and discharges into the Rock River. Figure 1.2 presents a Station Property Map showing the Station structures and the approximate property boundary.

2.2 OVERVIEW OF COOLING WATER OPERATIONS Operations at the Station began in 1985. The two nuclear reactors at the Station (Unit 1 and Unit 2) are both pressurized water reactors. The Station produces approximately 2,400 megawatts of electricity.

Non-contact cooling water from the Rock River that is used in the electricity generation process is cooled through the Station's two cooling towers. The water is then recirculated through the flume and discharged through the blowdown line back to the Rock River in accordance with an Illinois Environmental Protection Agency (Illinois EPA) National Pollution Discharge Elimination System (NPDES) permit (IL0048313) and Nuclear Regulatory Commission (NRC) Operating Licenses, NPF-37 (Unit 1) and NPF-66 (Unit 2).

Water from the Station's Radioactive Waste Treatment system is transferred to the liquid Radioactive Waste Storage Tank where it is sampled and analyzed. Once the analysis is reviewed and the water is determined to be in compliance with the NPDES permit and 045136 (13) Byron Generating Station 2 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 the NRC Operating License discharge limitations, it is batch released through the blowdown line.

The blowdown line and make-up line were constructed adjacent to each other and follow a northwest and then westerly path from the Station for approximately 2 miles to the Rock River. At the Rock River, the make-up line is located approximately 300 feet upstream of the blowdown line. Along the length of the two lines, there are six vacuum breaker (VB) locations (VB-1 through VB-6) for each line. The breakers are located within concrete vaults. There are two vaults at each breaker location, one for each line.

There are seven ponds in the northeast section of the Station. Six of these ponds are concrete-lined process catch basins and are aligned in an east-west trending series.

These are referred to as the Treated Runoff ponds. The four western ponds collect water from the Station; the water from these four ponds is pumped to the waste treatment building for processing. The two eastern ponds collect rainwater from the storm water drain system; the water from these ponds is pumped to the Construction Run-off Pond (CROP) located north of the Treated Runoff ponds. The CROP is lined at the bottom with 1 foot of clay. Water from the CROP is eventually pumped back into the Station's cooling towers.

2.3 SURROUNDING LAND USE The land surrounding the Station in all directions is primarily farmland. Approximately 0.3 mile north of the Station property along the Rock River is a small residential subdivision named Rock Terrace. In addition, there are two small residential areas along the Rock River approximately 0.1 mile and 0.8 mile south of the Station property.

The Byron Salvage Superfund Site (Byron Salvage Site) is immediately to the north of the west portion of the Station along Razorville Road. The Byron Salvage Site is administered by United States Environmental Protection Agency (USEPA) Region 5. It was placed on the National Priorities List (NPL) in 1982 and has the USEPA identification number ILD010236230. The Byron Salvage Site consists of two separate properties: the Byron Salvage Yard property and the Dirk's Farm property (see Figure 1.2). The Dirk's Farm property is currently owned by Exelon, and is a former farm located west of the Byron Salvage Yard property across Razorville Road.

Waste disposal at the Byron Salvage Site is known to have occurred on each of the two properties. From the mid 1960s to 1972, approximately 10 acres of the Byron Salvage Site were used as an automotive salvage yard and dump where miscellaneous waste 045136 (13) Byron Generating Station 3 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 and debris were disposed. Such wastes and debris included drums of electroplating wastes and other materials including oil sludges, cutting wheels, solvents, scrap metal, and industrial wastes. Plating waste containing cyanide was sprayed onto roads as dust control at the Byron Salvage Site.

At the direction of Illinois EPA, from 1974 through 1976 Exelon's predecessor, Commonwealth Edison Company (ComEd) removed the waste material from the Dirks Farm property. After 1976, ComEd continued monitoring the groundwater at the Dirks Farm property. Investigative and remedial actions were conducted at the Byron Salvage Yard portion of the Site beginning in 1983. Drums were present at the Byron Salvage Yard on the surface and buried underground. Hazardous wastes were found to contain lead, arsenic, cyanides, halogenated organics, zinc, nickel, and low concentrations of polychlorinated biphenyls (PCBs). Between 1986 and 1998, soil removal and cleanup activities were conducted on the Byron Salvage Site. The Byron Salvage Site remediation is in the long-term groundwater monitoring phase for volatile organic compounds (VOCs) and cyanides. ComEd resolved its alleged liability for the Byron Salvage Site in a settlement with USEPA.

2.4 STATION SETTING The following sections present a summary of the topography, surface water features, geology, hydrogeology, and groundwater flow conditions in the region surrounding the Station. The information was primarily gathered from Sections 2.1 and 2.5 of the Byron Station Updated Final Safety Analysis Report (UFSAR), Revision 10 dated December 2004, and from the well logs contained in the Byron Salvage Yard Remedial Design Work Plan (CRA, June 2001). The main references that the UFSAR relied upon are listed in Section 10.0 of this HIR. CRA checked and verified all UFSAR references that apply to this HIR.

2.4.1 TOPOGRAPHY AND SURFACE WATER FEATURES The Station's location is on the Oregon, Illinois 7.5-minute United States Geological Service (USGS) quadrangle topographic maps, dated 1976 (Stillman Valley) and 1983 (Oregon) (see Figure 1.1). The property boundaries fall within the following sections of the map: T24N R10E Sections 12, 13, 14, 15, 22, 23, and 24, and T24N R11E Sections 7, 18, and 19. The Byron, Illinois area is part of the Rock River Hill Country physiographic subsection. The Rock River Hill Country is characterized by gently rolling, dissected uplands covered by thin deposits of glacial drift overlain by a thin cap of loess. The 045136 (13) Byron Generating Station 4 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 southwest-trending Rock River valley passes through the eastern portion of the subsection. Bedrock is exposed locally along the Rock River and along small tributary streams and valleys of the Rock River. The topography that is indicated on the Oregon, Illinois 7.5-minute quadrangle is consistent with this physiography.

The Station was constructed on a local topographic high. In each direction from the Station, the topography undulates, with rolling hills and valleys. Along the Rock River, erosional valleys cut by tributary streams are present. The ground surface elevation at the Station is approximately 200 feet higher than the ground surface near the Rock River.

The Rock River, the largest body of water in the area, is located approximately 2 miles to the west of the Station. The river flows southward with an average flow of 4,000 cubic feet per second (cfs) and is primarily used for recreation, including boating, fishing, and water skiing. Streams in the Byron area discharge into the Rock River; the confluence of the Rock River with the Mississippi River is approximately 115 river miles south of the Station (Willman, et al., 1967).

The Woodland Creek is located to the north of the Station and flows to the northwest toward the Rock River. Additionally, an unnamed creek is located to the west of the Station and flows west toward the Rock River. Both of these creeks are ephemeral, flowing only during times of heavy rainfall.

2.4.2 GEOLOGY The northern portion of the mid-western United States is in the Central Lowlands Physiographic Province (Willman et al., 1975). This physiographic province has been divided into several physiographic sections. Parts of northern Illinois are located in the Wisconsin Driftless Section, the Till Plains Section, and the Great Lake Section.

Byron Station is located within the Till Plains Section. The Till Plains Section is characterized, in general, by the presence of glacial deposits overlying the bedrock surface. Local outcrops of bedrock are present. The Till Plains Section in Illinois is further subdivided into the following physiographic subsections: the Rock River Hill Country, the Green River Lowland, the Bloomington Ridged Plain, the Galesburg Plain, the Kankakee Plain, and the Springfield Plain. The Byron Station is in the Rock River Hill Country physiographic subsection (Willman et al., 1975).

The soil units in the region, adjacent to the Station, are relatively thin or locally absent.

They include alluvial deposits associated with the rivers and streams in the area, glacial 045136 (13) Byron Generating Station 5 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 deposits of till and outwash generally located in the upland areas, thin loess deposits that overlie the till, and locally, some thin residual soils developed from the weathering of the bedrock.

The Station is underlain by a veneer of overburden deposits that vary in thickness from less than 1 foot to approximately 12 feet and consist mainly of silty loam and loess, with alluvial deposits near the Rock River. The predominant soil types at the Station are the Martinsville Silt Loam, the Whalen Loam, and the Lamont Sandy Loam (Ogle County, 2006). These three soil types consist of loamy soil with varying amounts of silt and sand, with slopes ranging from 2 to 18 percent (United States Department of Agriculture, 2006).

The distribution of the rock units that form the bedrock surface within the region include a sedimentary sequence of Cambrian to Cretaceous-rocks and an igneous and metamorphic complex of Precambrian-aged rocks. The sedimentary sequence in northern Illinois near the Station includes Ordovician-aged and Cambrian-aged strata.

These strata consist of 2,000 to 3,000 feet of dolomites, sandstones, and shales. The Precambrian basement in northern Illinois consists of granites and granodiorites (Bradbury and Atherton, 1965).

The Byron Station lies within the Central Stable Region tectonic province of the North American continent. This tectonic region is characterized by a sequence of southward-thickening sedimentary strata overlying the Precambrian basement and was subjected to a series of vertical crustal movements forming broad basins and arches during Paleozoic and early Mesozoic time. Local folding and faulting has modified the arches and basins (Buschbach, 1964) (Willman et al., 1975).

The bedrock under the Station is comprised of flat-lying Ordovician-aged dolomitic and sandstone layers progressing downward as follows:

Galena Group Dolomites;

Platteville Group Dolomites; and

Ancell Group, consisting of:

Glenwood Formation (shale with sandy dolomite, semi-confining layer),

St. Peter Sandstone Formation, and older Cambrian formations.

The generating facility was constructed on an area of a 'bedrock high', and the foundation was installed into the bedrock. Figures 2.1 and 2.2 present generalized 045136 (13) Byron Generating Station 6 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 cross-sections of the area geology prepared from geologic information gathered from boreholes advanced prior to construction of the Station. The locations of the cross-sections are shown on Figure 1.2.

CRA has prepared hydrogeologic cross-sections depicting the geology and groundwater elevations under the Station. These figures are discussed in Section 5.0 of this Report.

2.4.3 HYDROGEOLOGY Ordovician-age Galena-Platteville dolomites and the older Ordovician-age Glenwood Formation and St. Peter Sandstone underlie the area. The most important aquifer in the region is the Cambrian-Ordovician Aquifer, made up of all bedrock between the top of the Galena-Platteville dolomites and the top of the Eau Claire Formation. These strata are, in descending order, the Ordovician-age Galena Formation, Platteville Formation, Ancell Formation (Glenwood, St. Peter, and older Cambrian formations), Prairie du Chien Formation, and Ironton and Galesville Sandstones. At the Bryon Station, the Galena-Platteville dolomites are separated from the rest of the Cambrian-Ordovician Aquifer by the Harmony Hill Shale Member of the Glenwood Formation. Available data indicate that, on a regional basis, the entire sequence of strata above the Eau Claire Formation behaves hydraulically as one aquifer. In places, pressure heads between the water bearing units differ, and the hydraulic connection is imperfect.

The Galena and Platteville Groups dolomites are extensively fractured near the top, with solutionally enlarged openings in places but become dense at depth. Water from the Galena-Platteville dolomites in the area is generally hard. Relatively low yields, water hardness, and susceptibility of the aquifer to contamination because of thin drift, fractures, and solution channels do not favor development of the Galena-Platteville dolomites.

Below the Galena-Platteville dolomites are the thin shales, sandstones, and limestones of the Glenwood Formation. This unit grades downward into the thick sandstones of the St. Peter Sandstone. The Ordovician-age St. Peter Sandstone is permeable and has a relatively uniform lithology throughout the area. The St. Peter Sandstone is recharged from overlying glacial deposits in the central and western parts of northern Illinois, and also by vertical leakage through the Maquoketa Shale Group in northeastern Illinois and by through-flow from the outcrop area in southern Wisconsin (Buschbach, 1964).

045136 (13) Byron Generating Station 7 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 2.4.3.1 EXISTING WELL NETWORK Groundwater (the water table) under the Station is first encountered within the Galena-Platteville limestones and dolomites. The depth to the groundwater varies with the topography, ranging from approximately 17 feet below ground surface (feet bgs) to 115 feet bgs. Near the Rock River, the water table is in the unconsolidated deposits.

There are 77 wells at the Station. Figure 2.3 presents the locations of the wells. Of the 77 wells, the Station owns 33 wells and the remaining 44 wells are owned by the Byron Salvage Site PRP Group. A summary of the existing well information is provided in Table 2.1. These wells were used during the investigations to provide information on the geology and groundwater levels at the Station.

The monitoring wells are set at different depths to screen all three hydrogeologic units located under the Station. CRA monitors the levels and water quality of the Byron Salvage Site wells at the Station as part of the long-term monitoring program for the Byron Salvage Site.

There are two deep wells in the Protected Area (PA). The wells are designated Deep Well 1 and Deep Well 2 and are used for the Station's water supply (see Figure 2.3).

Both wells were installed during the construction of the Station and draw water from depths greater than 500 feet below grade at an average flow rate of 800 gallons per minute (gpm) per well. Water is pumped from each well at different times, and the piping from the wells combines into a common manifold to supply the Station's water supply.

There are two former farmhouse water supply wells on the Station. The wells are designated GW-9 and Well 7. During an investigation of the blowdown line, which began in early 2006 (refer to Section 3.3.2.2), 16 overburden monitoring wells and 13 bedrock wells were installed along the blowdown line and also within the PA.

Further details regarding the most recent monitoring wells are provided in Section 3.4 of this report.

CRA expects most of the private wells in the vicinity of the Station are completed in the St. Peter Sandstone, however, well completion information was not available for all private wells identified by CRA, in order to confirm this observation.

045136 (13) Byron Generating Station 8 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 2.4.3.2 GROUNDWATER FLOW Groundwater flow in the Galena-Platteville dolomites occurs along joints and bedding planes. Solutioning along these pathways continues at an imperceptible rate due to the low solubility of the dolomite, the hardness of the groundwater, and the relatively low hydraulic gradient within the aquifer.

The general regional groundwater flow direction in the Galena-Platteville dolomites and the underlying Glenwood Formation and St. Peter Sandstone is to the west toward the Rock River. Local groundwater flow conditions are typically influenced by surface topography and aquifer thickness.

Groundwater flow patterns vary under the Station property. In July 1974, the Station assessed groundwater flow using a system of wells and piezometers installed prior to Station construction. Since the facility sits upon a bedrock high, groundwater flow directly beneath the facility was radially outward in all directions. Figure 2.4 presents the groundwater flow for the Station.

On the western portion of the Station near the blowdown line, groundwater flow was historically assessed as part of the Byron Salvage Site remedial investigation. CRA measured water levels at the Byron Salvage Site monitoring wells on March 23, 2006.

Groundwater contours for the entire Station (both the blowdown line area and the generating facility), are shown on Figure 2.4 which presents a combined generalized contour map of the 1974 data (for the generating facility) and the March 2006 data (for the blowdown line area). There is a northwest/southeast trending groundwater divide near Razorville Road, west of the generating facility, and perpendicular to the blowdown line. The direction of groundwater flow at points along the blowdown line varies depending upon the location. However, the general groundwater flow direction is to the west toward the Rock River.

2.5 AREA GROUNDWATER USE RETEC completed a water well search and survey for the Station property ("Residential Well Survey", RETEC Group, Inc, September 23, 2005). CRA expanded the water well search between March and May 2006 to identify the public and private water wells located within approximately 1 mile of Station property. CRA contacted the following sources for information:

045136 (13) Byron Generating Station 9 CONESTOGA-ROVERS & ASSOCIATES

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Illinois State Water Survey (ISWS);

Illinois State Geological Survey (ISGS);

Illinois EPA database; and

Ogle County GIS system.

The ISGS (in association with the Illinois EPA) and the ISWS maintain databases of water well information. The ISWS and ISGS provided lists of water wells for the Station and for the area surrounding the Station. A figure of the approximate locations of the water wells surrounding the Station (Figure A.1), along with copies of the information gathered from the ISWS and ISGS are provided in Appendix A. All of the water wells listed are for residential use; none are listed for commercial, industrial, or public water supply uses.

The St. Peter Sandstone is the primary aquifer for residential potable water in the area.

The most important aquifer in the region is the Cambrian-Ordovician Aquifer, made up of all bedrock between the top of the Galena-Platteville dolomites and the top of the Eau Claire Formation.

Potable water for the residences south, east, and some north of the Station is provided by private water wells at each property. As part of the Byron Salvage Site groundwater remediation, an alternate water supply and distribution system was provided to many of the residences located north of the Station.

045136 (13) Byron Generating Station 10 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 3.0 AREAS FOR FURTHER EVALUATION CRA considered all Station operations in assessing groundwater quality at the Station.

During this process, CRA identified areas at the Station that warranted further evaluation or "AFEs". This section discusses the process by which AFEs were selected.

CRA's identification of AFEs involved the following components:

Station inspection on March 21 and 22, 2006;

interviews with Station personnel;

evaluation of Station systems;

investigation of confirmed and unconfirmed releases of radionuclides; and

review of previous Station investigations.

CRA analyzed the information collected from these components combined with information obtained from CRA's study of hydrogeologic conditions at the Station to identify those areas where groundwater potentially could be impacted from operations at the Station.

CRA then designed an investigation to determine whether any confirmed or potential releases or any other release of radionuclides adversely affected groundwater. This entailed evaluating whether existing Station groundwater monitoring systems were sufficient to assess the groundwater quality at the AFEs. If the systems were not sufficient to adequately investigate groundwater quality associated with any AFE, additional monitoring wells were installed by CRA.

The following sections describe the above considerations and the identification of AFEs.

The results of CRA's investigation are discussed in Section 5.0.

3.1 SYSTEMS EVALUATIONS Exelon launched an initiative to systematically assess the structures, systems and components that store, use, or convey potentially radioactively contaminated liquids.

Maps depicting each of these systems were developed and provided to CRA for review.

The locations of these systems are presented on Figures 3.1 through 3.3. The Station identified a total of 30 systems that contain or could potentially contain radioactively contaminated liquids. The following presents a list of these systems.

045136 (13) Byron Generating Station 11 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 System Identification Description AB Boric Acid Process AS Auxiliary Steam BR Boron Thermal Regeneration CD Condensate CP Condensate Polishing CW Circulating Water DM Miscellaneous Building Drain DV Miscellaneous Drains and Vents FC Fuel Pool Cooling FP Fire Protection GS Turbine Gland Seals HD Feedwater Drains MS Main Steam OD Equipment/Floor Oil Drain PS Process Sampling PW Primary Water RF Reactor Building Floor Drains SH Station Heat SI Safety Injection ST Sewage Treatment SX Essential Service Water TE Turbine Building Equipment Drains TF Turbine Building Floor Drains TR Treated Runoff VF Filtered Vents VR Volume Reduction WE Auxiliary Building Equipment Drain WF Auxiliary Building Floor Drain WS Non-Essential Service Water WX Radwaste Disposal After these systems were identified, Exelon developed a list of the various structures, components and areas of the systems (e.g., piping, tanks, process equipment) that handle or could potentially handle any radioactively contaminated liquids. The structures, components, and areas may include:

aboveground storage tanks;

condensate vents;

areas where confirmed or potential historical releases, spills or accidental discharges may have occurred; 045136 (13) Byron Generating Station 12 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

pipes;

pools;

sumps;

surface water bodies (i.e., basins, pits, ponds, or lagoons);

trenches;

underground storage tanks; and

vaults.

The Station then individually evaluated the various system components to determine the potential for any release of radioactively contaminated liquid to enter the environment. Each structure or identified component was evaluated against the following seven primary criteria:

location of the component (i.e., basement or second floor of building);

component construction material (i.e., stainless steel or steel tanks);

construction methodologies (i.e., welded or mechanical pipe joints);

concentration of radioactively contaminated liquid stored or conveyed;

amount of radioactively contaminated liquid stored or conveyed;

existing controls (i.e., containment and detection); and

maintenance history.

System components, which were located inside a building or that otherwise had some form of secondary containment, such that a release of radioactively contaminated liquid would not be discharged directly to the environment, were eliminated from further evaluation. System components that are not located within buildings or did not have some other form of secondary containment were retained for further qualitative evaluation of the risk of a release of radioactively contaminated liquid to the environment and the potential magnitude of any release.

Exelon's risk evaluation took into consideration factors such as:

the potential concentration of radionuclides;

the volume of liquid stored or managed;

the probabilities of the systems actually containing radioactively contaminated liquid; and 045136 (13) Byron Generating Station 13 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

the potential for a release of radioactively contaminated liquid from the system component.

These factors were then used to rank the systems and system components according to the risk for a potential release of a radioactively contaminated liquid to the environment.

The evaluation process resulted in the identification of structures, components, and areas to be considered for further evaluation.

3.2 HISTORICAL RELEASES CRA also reviewed information concerning confirmed or potential historical releases of radionuclides at the Station, including reports and documents previously prepared by Exelon and compiled for CRA's review. CRA evaluated this information in identifying the AFEs. Any historical releases identified during the course of this assessment that may have a current impact on Station conditions are further discussed in Section 3.4.

3.3 STATION INVESTIGATIONS CRA also considered previous Station investigations in the process of selecting the AFEs for the Station. This section presents a summary of the pre-operational radiological environmental monitoring program (pre-operational REMP), past Station investigations, and the radiological environmental monitoring program (REMP).

3.3.1 PRE-OPERATIONAL RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM A pre-operational REMP was conducted between 1981 and 1984 to establish background radioactivity levels prior to operation of the Station. While a summary report for the pre-operational REMP was not available to CRA, CRA reviewed the pre-operational REMP data. An April 1987 REMP report prepared by Teledyne Isotopes Midwest Laboratory entitled "Radioactive Waste and Environmental Monitoring Annual Report 1986" identifies that a comparison of the 1985 and 1986 data to the pre-operational REMP data indicates that there was no measurable amount of radioactivity due to the Station's operation.

045136 (13) Byron Generating Station 14 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 3.3.2 RADIOLOGICAL ENVIRONMENTAL MONITORING PROGRAM The REMP at the Station was initiated in 1985. The REMP includes the collection of multi-media samples including air, surface water, groundwater, fish, sediment, vegetation, local cow milk, and residential potable water. The samples are analyzed for beta and gamma-emitting radionuclides, tritium, iodine-131, and/or strontium as established in the procedures developed for the REMP. The samples are collected at established locations, identified as stations, so that trends in the data can be monitored.

An annual report is prepared providing a description of the activities performed and the results of the analysis of the samples collected from the various media. The latest report generated was prepared by Station personnel and is entitled "Radioactive Effluent Release Report - January 2005 Through December 2005." This report concluded that the operation of the Station had no adverse radiological impact on the environment. The annual report is submitted to the NRC.

3.3.3 HISTORIC INVESTIGATIONS This section summarizes historic investigations undertaken at the Station prior to this hydrogeologic investigation, related to actual or potential releases of radioactively contaminated liquids to the subsurface.

3.3.3.1 POWER PLANT DOCUMENTS - UFSAR REPORT During the construction of the Station, a series of comprehensive investigations of regional and local geology, surface water, and groundwater conditions were conducted.

These studies are documented in the UFSAR, Rev. 10, dated December 2004 (Byron Station UFSAR, 2004).

3.3.3.2 BLOWDOWN LINE INVESTIGATION In July 2005, water was observed in the concrete vault for vacuum breaker 6 (VB-6). A water sample collected from the concrete vault, at that time, contained less than 2,000 picoCuries per liter (pCi/L) of tritium.

045136 (13) Byron Generating Station 15 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 In January 2006, the Station initiated an investigation into the blowdown line. A program of inspections of the concrete vaults, along with routine observations for water within the vaults was begun. Subsequent to the initial discovery of water in the vaults, Exelon performed construction upgrades on each of the six breaker vaults. These upgrades are intended to ensure that there will be no future releases of potentially contaminated liquid to the subsurface.

3.4 IDENTIFIED AREAS FOR FURTHER EVALUATION CRA used the information presented in the above sections along with its understanding of the hydrogeology at the Station to identify AFEs, which were a primary consideration in the development of the scope of work in the Work Plan. The establishment of AFEs is a standard planning practice in hydrogeologic investigations to focus the investigation activities at areas where there is the greatest potential for impact to groundwater.

Specifically, AFEs were identified based on these six considerations:

systems evaluations;

risk evaluations;

review of confirmed and/or potential releases;

review of documents;

review of the hydrogeologic conditions; and

Station inspection completed on March 22 and 23, 2006.

Prior to CRA completing its analysis and determination of AFEs, Station personnel completed an exhaustive review of all historic and current management of systems that may contain potentially radioactively contaminated liquids.

CRA reviewed the systems identified by the Station, which have the potential for the release of radioactively contaminated liquids to the environment, and groundwater flow at the Station. This evaluation allowed CRA to become familiar with Station operations and potential systems that may impact groundwater. CRA then evaluated information concerning historic releases as provided by the Station. This information, along with a review of the results from historic investigations, was used to refine CRA's understanding of areas likely to have the highest possibility of impacting groundwater.

Where at risk systems or identified historical releases were located in close proximity or were located in areas which could not be evaluated separately, the systems and 045136 (13) Byron Generating Station 16 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 historical releases were combined into a single AFE. At times, during the Station investigation, separate AFEs were combined into one or were otherwise altered based on additional information and consideration.

Finally, CRA used its understanding of known hydrogeologic conditions (prior to this investigation) to identify AFEs. Groundwater flow was an important factor in deciding whether to combine systems or historical releases into a single AFE or create separate AFEs. For example, groundwater beneath several systems that contain radioactively contaminated liquids that flows toward a common discharge point were likely combined into a single AFE. The AFEs were created based on known groundwater flow conditions prior to the work completed during this investigation.

Based upon its review of information concerning confirmed or potential historical releases, historic investigations, and the systems at the Station that have the potential for release of radioactively contaminated liquids to the environment combined with its understanding of groundwater flow at the Station, CRA identified three AFEs (see Figures 3.1 through 3.3).

AFE-Byron Former Fiberglass Blowdown Line This AFE is the area in which, in April 1986, after the initial six months of Unit 1 operation, there were three separate ruptures of the original fiberglass blowdown line.

The three ruptures were all in the same area, near River Road (Figure 3.1). Soil and water samples collected as part of the investigation of each rupture indicated the presence of minimal amounts of radioactive material. Following the ruptures, the Station replaced sections of the fiberglass blowdown line. The Station subsequently abandoned the entire line in place and installed a new carbon steel blowdown line in 1987.

AFE-Byron Vacuum Breaker Vaults In December 2005/January 2006, water was observed in the vacuum breaker vaults.

Exelon initiated an investigation into potential groundwater impact near all 12 vacuum breaker vaults (Figure 3.2), plugged the drainage holes and sealed all six blowdown line vaults.

AFE-Byron Protected Area Based on the risk ranking, several systems within the PA scored high as systems in which tritiated water could be released to the environment if a failure or if a set of events 045136 (13) Byron Generating Station 17 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 were to occur. These systems include: systems located within the Auxiliary Building, Radwaste Building, Containment Building, and the Turbine Building, the Condensate and Condensate Polishing systems, the Fuel Handling Building systems, the Circulating Water Pump House systems, and the CROP.

To evaluate the groundwater quality in the area of these systems, monitoring wells were installed in locations that are hydraulically downgradient of the AFE (Figure 3.3). The downgradient locations of the monitoring wells were selected based on the radial groundwater flow outward from the PA (Figure 2.4) due to the topographic high on which the PA was constructed. These monitoring well locations were situated to provide for adequate indication of historic releases and future leak detection.

045136 (13) Byron Generating Station 18 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 4.0 FIELD METHODS CRA and Station personnel completed two investigations at the Station:

the blowdown line investigation; and the fleetwide investigation.

During the blowdown line investigation conducted from February through April 2006, CRA oversaw the installation and development of 12 temporary and 17 permanent monitoring wells at the Station. CRA and Station personnel collected multiple samples from the vacuum breaker vaults, from nearby residential wells, from the blowdown line itself, from holding ponds, and from the existing and the CRA-installed monitoring wells.

During the fleetwide investigation completed in April and May 2006, CRA conducted a second round of groundwater sampling of 41 monitoring wells, collected a full round of water level measurements from 63 monitoring wells, and surveyed five monitoring wells that had not been surveyed as part of the blowdown line investigation. The field investigations were completed in accordance with the methodologies presented in the Work Plan (CRA, 2006).

The following sections discuss the field activities conducted during these two investigations.

4.1 BLOWDOWN LINE INVESTIGATION ACTIVITIES 4.1.1 GROUNDWATER MONITORING WELL INSTALLATION Prior to completing any ground penetration activities, CRA completed subsurface utility clearance procedures to minimize the potential of injury to workers and/or damage to subsurface utility structures. The subsurface clearance procedures consisted of completing an electronic survey within a minimum of 10-foot radius of the proposed location utilizing electromagnetic and ground penetrating radar technology.

Additionally, an air knife was utilized within the PA to verify utilities were not present at the proposed location to a depth to 10 feet bgs.

From late February 2006 to early April 2006, CRA supervised the installation of 17 monitoring wells and 12 temporary wells along the blowdown line and at other 045136 (13) Byron Generating Station 19 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 locations at the Station to evaluate the quality of the groundwater in the areas of the three AFEs. The monitoring well locations are presented on Figure 2.3.

Monitoring wells TW-13 through TW-15 were installed to evaluate the groundwater quality near River Road, downgradient of the 1986 former fiberglass blowdown line ruptures (AFE-Byron-1). These wells were originally constructed as temporary wells, but were eventually converted to permanent monitoring wells.

For AFE-Byron-2, at each of the six vacuum breaker vault locations along the blowdown line, two temporary wells were installed adjacent to the concrete vault and within the bedding material of the blowdown line and make-up line (TW-1 through TW-12). These shallow overburden wells were installed to determine whether groundwater was present in the overburden materials above the bedrock. These 12 temporary wells were dry.

Twelve monitoring wells (AR-1 through AR-10, CAR-2, and CAR-3) were installed to screen the first occurrence of groundwater (the water table) within the Galena-Platteville limestones and dolomites. One well was placed adjacent to each vacuum breaker vault (AR-1 through AR-6) in an anticipated downgradient location as determined from historic groundwater elevations measured in the Byron Salvage Site monitoring wells and levels measured in early March 2006. Monitoring well CAR-2 was installed at a location at the bottom of the valley downgradient from the vault for vacuum breaker 4, which contained water with the highest concentrations of tritium. Five monitoring wells (AR-7 through AR-10 and CAR-3) were installed within and around the PA to evaluate the groundwater quality in the areas of the high-ranking systems (AFE-Byron-3).

Two additional monitoring wells were also installed. Monitoring well CAR-1 was screened in the alluvial sediments adjacent to TW-14 to evaluate the groundwater quality approximately 20 feet below the water table. Due to detections of tritium concentrations in groundwater samples from monitoring well AR-4, monitoring well AR-11 was screened to monitor the groundwater quality at the base of the Galena-Platteville aquifer. In total, 13 bedrock monitoring wells were constructed as part of the blowdown line investigation.

The bedrock monitoring wells were all installed using a combination of augering, coring, and air rotary drilling techniques. The monitoring wells with the AR designation were drilled using air rotary techniques, and the wells with the CAR designation were first cored prior to using rotary techniques. The coring was planned to be completed at three locations to confirm the geology that was already expected based on the drilling logs from the Byron Salvage Site monitoring wells. The exception to the 045136 (13) Byron Generating Station 20 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 nomenclature designation is monitoring well CAR-1. Because the bedrock was not encountered at the base of the hill near River Road, coring was not necessary, and CAR-1 was augered to the target depth.

Specific installation protocols for the monitoring wells (other than the shallow temporary wells TW-1 through TW-12) are described below:

the borehole was advanced to the target depth using one of the drilling techniques listed above;

a nominal 2-inch diameter (No. 10 slot) PVC screen, of varying length, attached to a sufficient length of 2-inch diameter schedule 40 PVC riser pipe to extend to the surface, was placed into the borehole;

a filter sand pack consisting of silica sand was installed to a minimum height of 2 feet above the top of the screen;

in most cases, a minimum 2-foot thick seal consisting of bentonite chips was placed on top of the sand pack;

the remaining borehole annulus was sealed to within 1 foot of the surface using a cement-bentonite grout; and

the remaining portion of the annulus was filled with concrete and a 6-inch diameter protective above-grade casing.

Table 2.1 presents a summary of the well information for the wells installed during the blowdown line investigation. All monitoring well locations are presented on Figure 2.3.

Monitoring well stratigraphic and instrumentation logs are provided in Appendix B.

The wells were surveyed for horizontal and vertical control by an Illinois-licensed professional surveyor.

4.1.2 GROUNDWATER MONITORING WELL DEVELOPMENT After installation, CRA developed the 29 monitoring wells installed during the blowdown line investigation.

To establish good hydraulic communication with the aquifer and reduce the volume of sediment in the monitoring well, monitoring well development was performed in accordance with the procedure outlined below:

045136 (13) Byron Generating Station 21 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

Monitoring wells were surged using a pre-cleaned surge block for a period of at least 20 minutes.

Water was purged from the monitoring well using a pneumatic submersible pump.

Groundwater was collected at regular intervals with the pH, temperature, and conductivity measured using field instruments. These instruments were calibrated daily according to the manufacturer's specifications. Additional observations such as color, odor, and turbidity of the purged water were recorded in the field book.

Development continued until the turbidity and silt content of the monitoring wells was significantly reduced and three consistent readings of pH, temperature, and conductivity were recorded, or a minimum of ten well volumes were purged.

A summary of the monitoring well development activities is provided in Table 4.1.

4.1.3 SURVEY The new monitoring wells were surveyed to establish reference elevations relative to mean sea level. The top of each well casing was surveyed to the nearest 0.01 foot relative to the North American Vertical Datum 88 (NAVD). The survey included the ground elevation at each well to the nearest 0.10 foot relative to the NAVD, and the well location to the nearest 1.0 foot.

4.1.4 GROUNDWATER ELEVATION MEASUREMENTS During the blowdown line investigation, CRA collected two full rounds of water level measurements from both the Station wells existing at the time and from Byron Salvage Site's monitoring wells located both on and off of the Station property. Synoptic water level measurements were collected on March 23, 2006 and April 4, 2006. Based on the measured depth to water from the reference point and the surveyed elevation of the reference point, the groundwater elevation was calculated. A summary of groundwater elevations for the two measuring events is provided in Table 4.2.

4.1.5 GROUNDWATER SAMPLE COLLECTION CRA conducted one round of groundwater sampling during the blowdown line investigation. A total of 39 monitoring wells were sampled during the event. These wells included 19 of the 23 wells owned by the Station (TW-1 through TW-12 were dry 045136 (13) Byron Generating Station 22 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 and the two deep wells are sampled on a quarterly basis and have never indicated tritium impacts) and 20 selected Byron Salvage Site monitoring wells located at the Station. The Byron Salvage Site wells were selected based on the proximity of the wells to the blowdown line, their location downgradient of the blowdown line, and in order to provide a vertical characterization of the groundwater quality.

CRA conducted this round of sampling March 7, 2006 to April 18, 2006. Most of the monitoring wells were sampled on more than one occasion during this time period.

Monitoring wells AR-11 and GW-9 were only sampled once. In addition, a total of 22 Byron Salvage Site monitoring wells were originally selected for sampling. However, Well 7 was not sampled because the old farmhouse pump and drop tube were still in the well and were not removed until April 2006, and well DF-13 could not be sampled due to an obstruction in the well that was later removed. CRA conducted the sampling using a combination of bailers and PVC and stainless steel submersible pumps, employing both slow purging and low flow purging techniques. A summary of the purging parameters is presented in Table 4.3, and a sample summary is presented in Table 4.4.

All groundwater samples were labeled with a unique sample number, the date and time, the parameters to be analyzed, the job number, and the sampler's initials. The samples were then packed in a cooler for screening by the Station and shipment to the project laboratory, Environmental, Inc., via overnight courier under chain-of-custody protocol for tritium analysis. Split samples were also collected for the NRC and Illinois Emergency Management Agency (IEMA) for tritium analysis simultaneously with the actual sample at every sample location. The split samples were delivered to the Station personnel for delivery to the NRC and IEMA.

The water purged from the Byron Salvage Site wells during the sampling event was placed into two plastic holding tanks at the Station pending characterization and disposal in accordance with the Station's NPDES permit.

4.2 FLEETWIDE INVESTIGATION ACTIVITIES 4.2.1 GROUNDWATER ELEVATION MEASUREMENTS On April 24, 2006, CRA collected a round of water level measurements from 63 of the 77 Station monitoring wells in accordance with the Work Plan. Based on the measured depth to water from the reference point and the surveyed elevation of the reference point, the groundwater elevation was calculated. A summary of groundwater 045136 (13) Byron Generating Station 23 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 elevations for the April 24, 2006 event is provided in Table 4.5. Water level measurements were collected using a portable electronic depth-to-water probe accurate to +/- 0.01 foot. The measurements were made from a designated location at the highest point on each well's inner riser or steel casing. The water level measurements were obtained using the following procedures:

the proper elevation of the meter was checked by inserting the tip into water and noting if the contact was registering correctly;

the tip was dried, and then slowly lowered into the well until contact with the water was indicated;

the tip was slowly raised until the light and/or buzzer just began to activate. This indicated the static water level;

the reading at the reference point was noted to the nearest hundredth of a foot.

the reading was then re-checked; and

the water level was then recorded, and the water level meter decontaminated prior to use at the next well location.

4.2.2 GROUNDWATER SAMPLE COLLECTION CRA conducted a second round of groundwater sampling from April 24 through April 28, 2006. A total of 41 monitoring wells were sampled during the second event.

These included the 39 wells sampled during the first event and wells DF-13 and Well 7.

At these monitoring well locations, CRA conducted the sampling using pneumatic bladder pumps or peristaltic pumps and dedicated polyethylene tubing to employ low flow purging techniques as described in Puls and Barcelona (1996).

The groundwater in the monitoring wells was sampled by the following low-flow procedures:

the wells were correctly located and identification numbers were verified;

a water level measurement was taken;

the well was sounded by carefully lowering the electronic depth-to-water probe to the bottom of the well (as to minimize penetration and disturbance of the well bottom sediment), and comparing the sounded depth to the installed depth to assess the presence of any excess sediment or drill cuttings; 045136 (13) Byron Generating Station 24 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

the pump or tubing was lowered slowly into the well and fixed into place such that the intake was located at the mid-point of the well screen, or a minimum of 2 feet above the well bottom/sediment level;

the purging was conducted using a pumping rate between 100 to 500 milliliters per minute (mL/min). Initial purging began using the lower end of this range. The groundwater level was monitored to ensure that a drawdown of less than 0.3 foot occurred. If this criterion was met, the pumping rate was increased dependent on the behavior of the well. During purging, the pumping rate and groundwater level were measured and recorded every 10 minutes;

the field parameters (pH, temperature, conductivity, oxidation-reduction potential (ORP), dissolved oxygen (DO), and turbidity) were monitored during the purging to evaluate the stabilization of the purged groundwater. Stabilization was considered to be achieved when three consecutive readings for each parameter, taken at 5-minute intervals, were within the following limits:

pH +/- 0.1 pH units of the average value of the three readings, Temperature +/- 3 percent of the average value of the three readings, Conductivity +/- 0.005 milliSiemen per centimeter (mS/cm) of the average value of the three readings for conductivity <1 mS/cm and

+/- 0.01 mS/cm of the average value of the three readings for conductivity >1 mS/cm, ORP +/- 10 millivolts (mV) of the average value of the three readings, DO +/- 10 percent of the average value of the three readings, and Turbidity +/- 10 percent of the average value of the three readings, or a final value of less than 5 nephelometric turbidity units (NTU);

once purging was complete, the groundwater samples were collected directly from the pump/tubing into the sample containers; and

in the event that the groundwater recharge to the monitoring well was insufficient to conduct low flow sampling procedure, the well was pumped dry and allowed to sufficiently recharge prior to sampling.

All groundwater samples were labeled with a unique sample number, the date and time, the parameters to be analyzed, the job number, and the sampler's initials. The samples were then packed in a cooler for screening by the Station and shipment to Teledyne Brown Engineering, Inc. (Teledyne Brown). A sample summary is presented in Table 4.6; field measurements for the fleetwide event are presented in Table 4.7.

045136 (13) Byron Generating Station 25 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 CRA containerized the water purged from all of the wells during the fleetwide event.

The water was placed into the two plastic holding tanks at the Station, pending characterization. The water was processed by the Station in accordance with their NPDES permit.

4.2.3 DATA QUALITY OBJECTIVES CRA has validated the analytical data to establish the accuracy and completeness of the data reported. Teledyne Brown provided the analytical services. The Quality Assurance Programs are described in Appendix C. Analytical data for groundwater samples collected in accordance with the Work Plan are presented in Appendix D. Data validation reports are presented in Appendix E. The data validation included the following information and evaluations:

sample preservation;

sample holding times;

laboratory method blanks;

laboratory control samples;

laboratory duplicates;

verify laboratory qualifiers; and

field quality control (field blanks and duplicates).

Following the completion of field activities, CRA compiled and reviewed the geologic, hydrogeologic, and analytical data.

The data were reviewed using the following techniques:

data tables and databox figures;

hydrogeologic cross-sections; and

hydraulic analyses.

4.2.4 SAMPLE IDENTIFICATION For the fleetwide sampling, systematic sample identification codes were used to uniquely identify all samples. The identification code format used in the field was:

045136 (13) Byron Generating Station 26 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 WG-BYN-042506-SS-01. A summary of sample identification numbers for the fleetwide investigation is presented in Table 4.6.

WG - Sample matrix -groundwater RB - Sample matrix - rinse blank BYN - Station code (for Byron) 042506 - Date (month/day/year)

SS - Sampler's initials 01 - Sample number 4.2.5 CHAIN-OF-CUSTODY RECORD The samples were delivered to Station personnel under chain-of-custody protocol.

Subsequently, the Station or CRA shipped the samples under chain-of-custody protocol to Teledyne Brown for analyses.

4.2.6 QUALITY CONTROL SAMPLES Quality control samples were collected to evaluate the sampling and analysis process.

Field Duplicates Field duplicates were collected to verify the accuracy of the analytical laboratory by providing two samples collected at the same location and then comparing the analytical results for consistency. Field duplicate samples were collected at a frequency of one duplicate for every ten samples collected. The locations of duplicate samples were selected in the field during the performance of sample collection activities. The duplicate samples were collected simultaneously with the actual sample and were analyzed for the same parameters as the actual samples.

Rinsate Blank Samples Rinsate blanks were collected during the fleetwide investigation to verify that decontamination procedures conducted in the field were adequate. Rinsate blanks were collected by routing Station-supplied demineralized water through decontaminated sampling equipment. Rinsate blanks were collected at a frequency of one rinsate blank 045136 (13) Byron Generating Station 27 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 for every day samples were collected using non-disposable or non-dedicated equipment.

A total of four rinsate blanks were collected.

Split Samples Split samples were collected for the NRC and IEMA for tritium simultaneously with the actual sample at every sample location. Split samples were delivered to the Station personnel and made available to the NRC and IEMA.

4.2.7 ANALYSES Groundwater samples were analyzed for tritium and gamma-emitting radionuclides as listed in NUREG-1301 and strontium-89/90 as listed in 40 CFR 141.25.

045136 (13) Byron Generating Station 28 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 5.0 RESULTS

SUMMARY

This section provides a summary of Station-specific geology and hydrogeology, along with a discussion of hydraulic gradients, groundwater elevations, and flow directions in the vicinity of the Station. This section also presents and evaluates the analytical results obtained from activities performed during the blowdown line and fleetwide investigations.

5.1 STATION GEOLOGY Bedrock under the Station is generally found within the top 10 feet, under a veneer of unconsolidated deposits, except near the Rock River, where the bedrock has been eroded and is encountered at deeper depths. The Station geology is consistent with the regional geology and is comprised of flat-lying Ordovician-aged dolomitic and sandstone layers progressing downward as follows:

Galena Group Dolomites;

Platteville Group Dolomites; and

Ancell Group, consisting of:

Glenwood Formation (shale with sandy dolomite, semi-confining layer),

St. Peter Sandstone Formation, and older Cambrian formations.

The generating facility was constructed on an area of a 'bedrock high', and the foundation was installed into the bedrock.

5.2 STATION HYDROGEOLOGY There are two aquifers within the first 230 feet beneath the Station property:

the upper aquifer is the Galena-Platteville aquifer consisting of Galena-Platteville limestones and dolomites; and

the lower aquifer is the St. Peter Sandstone aquifer.

The Glenwood Formation separates the above two aquifers. The Glenwood contains shale at the top and sandy dolomite at its base. The shale acts as a semi-confining aquitard between the upper Galena-Platteville aquifer and lower St. Peter Sandstone 045136 (13) Byron Generating Station 29 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 aquifer. The first occurrence of groundwater (the water table) is encountered within the unconsolidated deposits near the Rock River, and within the upper fractured portions of the Galena-Platteville aquifer in the upland areas, east of the Rock River.

The monitoring wells at the Station were installed to monitor three intervals within the two aquifers (see Table 2.1):

wells screened across the water table, either in the unconsolidated sediments near the Rock River or in the upper portions of the Galena-Platteville aquifer;

wells screened at the bottom of the Galena-Platteville aquifer, just above the shale unit; and

wells screened in the St. Peter Sandstone aquifer.

Figure 5.1 presents the locations of four hydrogeologic cross-sections prepared for the Station. The four cross-sections depict the relationship between the geology and measured groundwater elevations. Figure 5.2 presents an east-west cross-section parallel to the groundwater flow direction, along the blowdown line. Figure 5.3 presents a north-south cross-section perpendicular to the groundwater flow, through vacuum breaker 4 (VB-4). This location was chosen because water with the highest concentrations of tritium was encountered in the concrete vault at VB-4. Also indicated on Figures 5.1 through 5.3 are the approximate limits of the historical Byron Salvage Site groundwater plumes. Figure 5.4 presents two cross-sections through the PA, one trending to the northeast through Unit 2 and the other to the east through Unit 2.

5.2.1 GROUNDWATER FLOW DIRECTIONS CRA used a commercially available contouring program (Surfer, Version 8.02, 2002) to provide an initial contouring of the measured groundwater elevations. CRA then refined the initial contours, using professional judgment, to prepare final contour maps.

Figure 2.4 presents the water table groundwater contours in the upper portion of the Galena-Platteville aquifer based on data collected by CRA on March 23, 2006 for the blowdown line area, along with historical data collected in 1974 for the generating facility area. Figures 5.5 through 5.7 present the groundwater contours based on April 24, 2006 data for the upper portion of the Galena-Platteville aquifer, the bottom of the Galena-Platteville aquifer, and the St. Peter Sandstone aquifer, respectively.

The general groundwater flow direction in all three intervals is to the west toward Rock River. This is consistent with the regional flow pattern, which is to the west toward the 045136 (13) Byron Generating Station 30 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 Rock River, since the Rock River is the major water body in the area (UFSAR, 2004 and CRA, 2001).

Within the upper portions of the Galena-Platteville aquifer, the direction of groundwater flow typically follows the topographic relief at points along the blowdown line. There is a northwest/southeast trending groundwater divide within the Former Dirk's Farm property, near Razorville Road, that is generally perpendicular to the blowdown line (Figures 2.4 and 5.5).

5.2.2 MAN-MADE INFLUENCES ON GROUNDWATER FLOW The PA sits upon a bedrock high, and as such, the groundwater beneath this area of the Station flows radially outward in all directions. The bedrock below the generating facility foundations was pressure grouted for structural reasons prior to constructing the foundation. The pressure grouting sealed the pore space of the bedrock, thus causing the groundwater to be observed at a deeper depth than that under normal conditions in AR-7. Therefore, the groundwater elevation from AR-7 was not used in the contouring of Figure 5.5.

5.2.3 VERTICAL HYDRAULIC GRADIENTS CRA calculated vertical hydraulic gradients at the locations where depth specific wells were clustered together. Table 5.1 presents the calculated vertical gradients. Between the upper portion of the Galena-Platteville aquifer and the bottom of the aquifer, there is a slight downward vertical gradient of approximately 0.01 feet/foot. This is consistent with the effects of recharge from the higher/elevated areas of the Station and discharge to the Rock River. However, at the PC-3B/DF-6 well cluster location on the former Dirk's Farm property, the downward vertical gradient is greater, at 0.443 feet/foot. The vertical gradients measured within the Galena-Platteville aquifer are in the same range as the measured horizontal hydraulic gradient.

There is only one cluster of wells in which both wells are screened within the St. Peter Sandstone aquifer: MW-20R and MW-21. The measured vertical hydraulic gradient at this well cluster is very low at 0.001 feet/foot. This suggests primarily horizontal flow within the St. Peter Sandstone aquifer, which is consistent with the high conductivity of the St. Peter Sandstone.

045136 (13) Byron Generating Station 31 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 The groundwater elevation data confirm that the Galena-Platteville and St. Peter Sandstone aquifers are not hydraulically connected. The groundwater elevations measured in wells that are screened in the St. Peter Sandstone aquifer are typically more than 50 feet lower than those in wells screened at the bottom of the Galena-Platteville aquifer. Vertical hydraulic gradients between these two aquifers, measured at five well clusters, range between 0.622 feet/foot and 1.893 feet/foot, with the average being 1.127 feet/foot. These are much greater than the horizontal gradients measured in either of the two aquifers. These groundwater data provide evidence that the shale of the Glenwood Formation, which separates the bottom of the Galena-Platteville aquifer from the underlying St. Peter Sandstone aquifer, is acting as a local aquitard or semi-confining unit.

5.2.4 LATERAL GROUNDWATER FLOW AND VELOCITY Across the more than two-mile distance between the generating facility and the Rock River, the water table elevation drops approximately 160 feet, creating a shallow horizontal hydraulic gradient of approximately 0.014 feet/foot. The limestones and dolomites that comprise the Galena-Platteville aquifer generally have hydraulic conductivities that can vary significantly; a study for the Byron Salvage Site immediately to the north of the west portion of the station, reported mean hydraulic conductivities ranging from 0.31 feet/day to 240 feet/day with a primary porosity of around 10 percent (Kay et al., 1997). With a gradient of 0.014 feet/foot, the average shallow horizontal groundwater flow velocity can be calculated to be 15.8 feet/year to 12,200 feet/year.

The groundwater flow direction at the bottom of the Galena-Platteville aquifer has a southwest component, under a horizontal hydraulic gradient of approximately 0.011 feet/foot (Figure 5.6). However, the wells screened at the bottom of the aquifer are only located near the blowdown line, on the Former Dirk's Farm property, not across the entire length of the Station property. In this same area for the upper Galena-Platteville aquifer, the groundwater contours also suggest a component of flow to the southwest.

In St. Peter Sandstone aquifer, the groundwater contours suggest a groundwater flow to the west toward the Rock River, under a low horizontal hydraulic gradient of approximately 0.001 feet/foot (Figure 5.7). This is consistent with expected regional groundwater flow within the lower aquifer. Using the hydraulic gradient of 0.001 feet/foot with a reported hydraulic conductivity range of 2.0 feet/day to 8.7 feet/day (Kay et al., 1997) and a reported primary porosity of 0.14 (Kay et al., 1997) 045136 (13) Byron Generating Station 32 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 yields an average horizontal groundwater velocity in the St. Peter Sandstone of 5.2 feet/year to 22.7 feet/year.

5.3 GROUNDWATER QUALITY During the blowdown line investigation and the fleetwide assessment, both CRA and Station personnel collected numerous samples from the vacuum breaker vaults and other Station locations, from nearby residential wells, from the blowdown line itself, from the on-Station CROP, and from a subset of the monitoring wells located on the Station property. As discussed in Sections 4.1 and 4.2, the samples were analyzed for tritium, and some of the samples were also analyzed for strontium-89/90 and additional radionuclides.

Table 5.2 presents a summary of tritium analyses for water samples collected by the Station from the vacuum breaker vaults, the beginning and end of the blowdown line, and the CROP. Table 5.3 presents a summary of tritium analyses for groundwater samples collected during both the blowdown line investigation and the fleetwide investigation. Table 5.4 presents a summary of tritium analyses for groundwater samples collected from residential water supply wells. Table 5.5 presents a summary of the other radionuclide analyses (strontium-89/90 and gamma-emitting radionuclides) for groundwater samples collected during both the blowdown line investigation and the fleetwide investigation.

The analytical data presented herein has been subjected to CRA's data validation process (see Appendix E for the data validation reports). CRA has used the data with appropriate qualifiers, where necessary.

The data reported in the figures and tables does not include the results of re-analyses or recounts that the laboratory completed, except if those results ultimately replaced an initial report. The tables and figures, therefore, include only the first analysis reported by the laboratory.

045136 (13) Byron Generating Station 33 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 5.3.1

SUMMARY

OF BETA-EMITTING RADIONUCLIDES ANALYTICAL RESULTS 5.3.1.1 STATION SAMPLING POINTS During the blowdown line investigation, Station personnel collected multiple samples on different dates from the vacuum breaker vaults, the beginning and end of the blowdown line, and the CROP. A summary of the tritium results for the water samples collected from the Station sampling locations is provided in Table 5.2. The tritium data are presented graphically on Figure 5.8.

5.3.1.2 GROUNDWATER MONITORING WELL SAMPLES A summary of the tritium results for the groundwater samples collected during both the blowdown line investigation and the fleetwide investigation is provided in Table 5.3.

Figures 5.9 through 5.11 present the tritium data graphically for the groundwater samples collected on different dates from the monitoring wells screened in the upper portions of the Galena-Platteville aquifer, the bottom of Galena-Platteville aquifer, and the St. Peter Sandstone aquifer, respectively.

All tritium concentrations were below the USEPA drinking water standard of 20,000 pCi/L. Tritium was not detected at concentrations greater than the LLD of 200 pCi/L in 35 of the 39 groundwater samples collected.

Strontium-89/90 was not detected at concentrations greater than the LLD of 2.0 pCi/L.

A summary of the strontium-89/90 results for the groundwater samples collected as part of the investigations that are the subject of this HIR is provided in Table 5.5.

Galena-Platteville Aquifer Groundwater samples were collected from 32 different monitoring wells screened in the upper portions of Galena-Platteville aquifer (Figure 5.9). Concentrations of tritium exceeding the LLD of 200 pCi/L for tritium were only detected in the groundwater samples collected from three of the monitoring wells: AR-2, AR-3, and AR-4. The most recent concentrations of tritium detected at each location were:

AR-2 432 +/- 140 pCi/L;

AR-3 234 +/- 128 pCi/L; and

AR-4 3,260 +/- 367 pCi/L.

045136 (13) Byron Generating Station 34 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 The original groundwater sample collected from TW-13 had a tritium concentration less than the LLD of 200 pCi/L; however, a detection of tritium slightly greater than the LLD, 201 +/- 110 pCi/L, was detected in a duplicate groundwater sample collected as part of the fleetwide sampling event at the same time on the same date. In consideration of the original sample being less than the LLD, and the duplicate sample at 201 pCi/L with an error of +/- 110 pCi/L, the tritium concentration at this location is regarded as less than the LLD.

CRA collected five groundwater samples from monitoring wells installed at the bottom of Galena-Platteville aquifer (Figure 5.10), and only the samples from monitoring well AR-11 contained tritium at concentrations greater than the LLD of 200 pCi/L. The highest tritium concentration detected in a groundwater sample collected from monitoring well AR-11 was 2,340 +/- 282 pCi/L. Monitoring well AR-11 is a bedrock well located in a downgradient direction from monitoring well AR-4 and VB-4 (Figure 2.3),

and screened in a deeper portion of the bedrock (bottom of the Galena-Platteville aquifer) than AR-4 (upper portion of the Galena-Platteville aquifer) (Figure 5.2). The inferred vertical limits of the groundwater containing tritium exceeding the LLD of 200 pCi/L are depicted on Figures 5.2 and 5.3.

Strontium-89/90 was not detected at concentrations greater than the LLD of 2.0 pCi/L.

A summary of the strontium 89/90 results for the groundwater samples collected as part of the investigations that are the subject of this HIR is provided in Table 5.5.

St. Peter Sandstone Aquifer CRA collected groundwater samples from four monitoring wells screened in the St. Peter Sandstone aquifer (Figure 5.11). None of the groundwater samples contained detectable concentrations of tritium above the LLD of 200 pCi/L.

Strontium-89/90 was not detected at concentrations greater than the LLD of 2.0 pCi/L.

A summary of the strontium-89/90 results for the groundwater samples collected as part of the investigations that are the subject of this HIR is provided in Table 5.5.

5.3.1.3 RESIDENTIAL WATER SUPPLY WELLS Station personnel collected water samples from nine of the residences located adjacent to the Station property, along the blowdown line. In addition, a water sample was also 045136 (13) Byron Generating Station 35 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 collected from the well of a residence located approximately 2 miles east of the Station (Goral Well) to be used as a background water sample.

Tritium was not detected above the LLD of 200 pCi/L in any of the 10 residential well samples collected. A summary of the tritium results for the residential water samples is provided in Table 5.4, and the tritium data is presented graphically on Figure 5.12.

Strontium-89/90 was not detected at concentrations greater than the LLD of 2.0 pCi/L.

A summary of the strontium-89/90 results for the groundwater samples collected as part of the investigations that are the subject of this HIR is provided in Table 5.5.

5.3.2

SUMMARY

OF GAMMA-EMITTING RADIONUCLIDES ANALYTICAL RESULTS Gamma-emitting target radionuclides were not detected at concentrations greater than their respective LLD. CRA collected groundwater samples from 19 monitoring wells and the samples were analyzed for gamma-emitting radionuclides. A summary of the radionuclide results is provided in Table 5.5 and presented graphically on Figure 5.13.

Other non-targeted radionuclides were also included in the tables but excluded from discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

5.3.3

SUMMARY

OF FIELD MEASUREMENTS A summary of the field measurement results for the groundwater samples collected as part of the blowdown line investigation is provided in Table 4.3. A summary of the field measurement results for the groundwater samples collected as part of the fleetwide investigation is provided in Table 4.7. These field measurements included pH, Dissolved Oxygen, Conductivity, Turbidity and Temperature.

045136 (13) Byron Generating Station 36 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 5.4 SURFACE WATER QUALITY No samples were collected from the surface water bodies. The two surface water drainage creeks located in the area of the Station are both ephemeral streams, flowing only during times of heavy rainfall.

045136 (13) Byron Generating Station 37 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 6.0 RADIONUCLIDES OF CONCERN AND SOURCE AREAS This section discusses radionuclides evaluated in this investigation, potential sources of the radionuclides detected, and their distribution.

6.1 GAMMA-EMITTING RADIONUCLIDES Gamma-emitting target radionuclides were not detected at concentrations greater than their respective LLD. Other non-targeted radionuclides were also included in the tables but excluded from discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

6.2 BETA-EMITTING RADIONUCLIDES Strontium-89/90 was not detected in any of the groundwater samples collected at concentrations greater than the LLD of 2.0 pCi/L. Tritium was detected in four of the 39 total sample locations. Concentrations of tritium ranged between 234 +/- 128 pCi/L to 3,260 +/- 367 pCi/L.

Since only tritium was detected at concentrations greater than its LLD during the fleetwide investigation, the following sections focus on tritium; specifically, providing general characteristics of tritium, potential sources, distribution in groundwater, and a conceptual model for migration.

6.3 TRITIUM This section discusses the general characteristics of tritium, the distribution of tritium in groundwater and surface water, and the conceptual model of tritium release and migration.

6.3.1 GENERAL CHARACTERISTICS Tritium (chemical symbol H-3) is a radioactive isotope of hydrogen. The most common forms of tritium are tritium gas and tritium oxide, which is also called "tritiated water."

045136 (13) Byron Generating Station 38 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 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 absorption through skin. Once tritium enters the body, it disperses quickly and is uniformly distributed throughout the body. Tritium is excreted primarily through urine within a month or so after ingestion. Organically bound tritium (tritium that is incorporated in organic compounds) can remain in the body for a longer period.

Tritium is produced naturally in the upper atmosphere when cosmic rays strike air molecules. Tritium is also produced during nuclear weapons explosions, as a by-product 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 normal water, tritiated water is colorless and odorless. Tritiated water behaves chemically and physically like non-tritiated water in the subsurface, and therefore 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 (low-energy electron). The radioactivity of tritium is the source of the risk of exposure.

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.

6.3.2 DISTRIBUTION IN STATION GROUNDWATER This section provides an overview of the lateral and vertical distribution of tritium found in groundwater beneath the Station. Tritium was only detected in groundwater at concentrations exceeding the LLD of 200 pCi/L near the vaults along the blowdown line.

The groundwater under the PA does not appear to be impacted by tritium based on the groundwater analytical results from the five monitoring wells installed in and around 045136 (13) Byron Generating Station 39 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 the PA (AR-7 through AR-10 and CAR-3) in locations that are hydraulically downgradient of Station systems. Tritium was not detected at concentrations greater than the LLD of 200 pCi/L in any of the groundwater samples collected from these five monitoring wells during the investigation.

Tritium was not detected at concentrations greater than the LLD of 200 pCi/L in the water samples collected from the residential water wells. The St. Peter Sandstone is the primary aquifer for residential potable water in the area, and the water in the St. Peter Sandstone aquifer is separated from the water in the Galena-Platteville aquifer by the shale unit of the Glenwood Formation (see Section 5.1.2).

The only tritium concentrations greater than the LLD of 200 pCi/L were detected during the blowdown line and fleetwide investigations in groundwater samples collected from four wells: AR-2, AR-3, AR-4, and AR-11. Monitoring wells AR-2, AR-3, and AR-4 screen the water table, and AR-11 is screened at the bottom of the Galena-Platteville aquifer. These four locations are adjacent to the three vacuum breaker vaults VB-2, VB-3, and VB-4, that had water within the concrete vaults exhibiting the highest concentrations of tritium (see Figure 5.8).

The tritium concentrations detected in the groundwater samples collected from monitoring wells AR-2 and AR-3, which are near VB-2 and VB-3, are not much higher than 200 pCi/L. The concentrations in these two wells fluctuate, but are all less than 600 pCi/L. The detected tritium concentrations in the groundwater samples collected during the fleetwide investigation from monitoring wells AR-4 and AR-11 were 3,260 +/- 367 pCi/L and 2,340 +/- 282 pCi/L, respectively. These wells are near VB-4. AR-4 screens the water table, and AR-11 is deeper and screens the bottom of the Galena-Platteville aquifer.

The original groundwater sample collected from TW-13 had a tritium concentration less than the LLD of 200 pCi/L; however, tritium was detected at a very low concentration, 201 +/- 110 pCi/L, in a duplicate groundwater sample collected as part of the fleetwide sampling event at the same time on the same date. In consideration of the original sample being less than the LLD, and the duplicate sample at just 201 pCi/L with an error of +/- 110, the tritium concentration at this location is regarded as less than the LLD.

Monitoring well TW-13 is a shallow well (18 feet deep) located near River Road and installed within the unconsolidated alluvial sediments.

In summary, there are only three areas at the Station where tritium has been detected.

They are all located near vacuum breakers along the blowdown line. These three areas are: VB-2 (well AR-2), VB-3 (well AR-3), and VB-4 (wells AR-4 and AR-11). The 045136 (13) Byron Generating Station 40 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 groundwater impacted at each of these areas is localized within the Galena-Platteville aquifer. The inferred vertical limits of the groundwater containing tritium exceeding 200 pCi/L are depicted on Figures 5.2 and 5.3. Based on the data collected, none of the other aquifers appears to have been impacted.

6.3.3 CONCEPTUAL MODEL OF TRITIUM RELEASE AND MIGRATION This section presents CRA's conceptual model of groundwater and tritium migration at the Station.

As identified in Section 6.3.2, the groundwater under the PA does not appear to be impacted by tritium above the LLD of 200 pCi/L. Tritium was also not detected at concentrations exceeding the LLD of 200 pCi/L in the water samples collected from the residential water wells.

The highest concentrations of tritium detected in the Station sampling points were from water samples collected from within the vacuum breaker vaults along the blowdown line. The source of the tritium in the groundwater at the four wells is minor failures of the blowdown line vacuum breakers. This water originated from the blowdown line.

The water encountered in the vaults was pumped out and processed in accordance with the Station's NPDES permit. As discussed in Section 3.3.2.2, Exelon performed construction upgrades on each of the six breaker vaults to ensure that there will not be any future releases of tritium to the groundwater.

Sources and Migration of Tritium The detections of tritium exceeding 200 pCi/L in monitoring wells AR-2, AR-3, AR-4, and AR-11 appear to be localized and confined to the areas around the wells. Tritium was not detected at the LLD of 200 pCi/L in the groundwater samples collected from monitoring wells and residential wells downgradient of these locations. The source of the tritium in the groundwater at these four well locations is the blowdown line vacuum breakers (AFE-Byron-2). Once in the subsurface, the tritiated water migrated downward through the unsaturated overburden and fractured bedrock to the water table. Once at the water table, downward vertical gradients caused the tritiated water to migrate downward to the base of the Galena-Platteville aquifer, where tritium was detected in the groundwater sample from monitoring well AR-11 (Figure 5.2).

The shale of the Glenwood Formation has a low permeability and acts as a barrier to further downward migration of the tritiated water. Due to the low permeabilities of the 045136 (13) Byron Generating Station 41 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 Galena-Platteville limestones/dolomites, combined with the shallow horizontal gradient, the tritiated water should not migrate very far laterally from the vacuum breakers. There is no indication from the HIR data that tritium-impacted groundwater in this area is migrating off the Station property.

045136 (13) Byron Generating Station 42 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 7.0 EXPOSURE PATHWAY ASSESSMENT This section addresses the groundwater impacts from tritium and other radionuclides at the Station and potential risks to human health and the environment.

Based upon historical knowledge and data related to the Station operations and based upon radionuclide analyses of groundwater samples, the primary constituent of concern (COC) is tritium. The discussions that follow are focused on the exposure pathways related to tritium.

Teledyne Brown reports all samples to their statistically-derived minimum detectable concentration (MDC) of approximately 150 to 170 pCi/L, which is associated with 95 percent confidence interval on their hardcopy reports. However, the laboratory uses a 99 percent (+/- 3-sigma) confidence range for determining whether to report the sample activity concentration as detected or not. This 3-sigma confidence range typically equates to 150 (+/- 135.75) pCi/L.

Exelon has specified a LLD of 200 pCi/L for the Fleetwide Assessment. Exelon has also required the laboratory to report related peaks identified at the 95 percent confidence level (2-sigma).

This HIR, therefore, screens and assesses data using Exelon's LLD of 200 pCi/L. As is outlined below, this concentration is also a reasonable approximation of the background concentration of tritium in groundwater at the Station.

7.1 HEALTH EFFECTS OF TRITIUM Tritium is a radionuclide that decays by emitting a low-energy beta particle that cannot penetrate deeply into tissue or travel far in air. A person's exposure to tritium is primarily through the ingestion of water (drinking water) or through ingestion of water bearing 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 skin is possible, but tritium exposure is more limited here versus direct ingestion or drinking of tritiated water.

045136 (13) Byron Generating Station 43 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

7.2 BACKGROUND

CONCENTRATIONS OF TRITIUM The purpose of the following paragraphs is to establish a background concentration through review of various media.

7.2.1 GROUNDWATER Tritium is created in the environment from naturally occurring processes both cosmic and subterranean, as well as from anthropogenic (i.e., man-made) sources. In the upper atmosphere, "cosmogenic" tritium is produced from the bombardment of stable nuclides and combines with oxygen to form tritiated water, which will then enter the hydrologic cycle. Below ground, "lithogenic" tritium is produced by the bombardment of natural lithium isotopes 6Li (92.5 percent abundance) and 7Li (7.5 percent abundance) present in crystalline rocks by neutrons produced by the radioactive decay of uranium and thorium. Lithogenic production of tritium is usually negligible compared to other sources due to the limited abundance of lithium in rock. The lithogenic tritium is introduced directly to groundwater.

A major anthropogenic source of tritium comes from the former atmospheric testing of thermonuclear weapons. Levels of tritium in precipitation increased during the 1950s and early 1960s, coinciding with the release of significant amounts of tritium to the atmosphere during nuclear weapons testing prior to the signing of the Limited Test Ban Treaty in 1963, which prohibited atmospheric nuclear tests.

7.2.2 PRECIPITATION DATA Precipitation samples are routinely collected at stations around the world for the analysis of tritium and other radionuclides. Two publicly available databases that provided tritium concentrations in precipitation are Global Network of Isotopes in Precipitation (GNIP) and USEPA's RadNet database. GNIP provides tritium precipitation concentration data for samples collected world wide from 1960 to 2006.

RadNet provides tritium precipitation concentration data for samples collected at Stations through the U.S. from 1960 up to and including 2006.

Based on GNIP data for sample stations located in the U.S. Midwest including Chicago, St. Louis and Madison, Wisconsin, as well as Ottawa Ontario, and data from the University of Chicago, tritium concentrations peaked around 1963. This peak, which approached 10,000 pCi/L for some stations, coincided with the atmospheric testing of 045136 (13) Byron Generating Station 44 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 thermonuclear weapons. Tritium concentrations showed a sharp decline up until 1975 followed by a gradual decline since that time. Tritium concentrations in Midwest precipitation have typically been less than 100 pCi/L since around 1980.

The RadNet database for several stations in the U.S. Midwest (Chicago, Columbus, Indianapolis, Lansing, Madison, Minneapolis, Painesville, Toledo, and Welsch, MN) did not show the same trend, which can be attributed to pre-1995 data handling procedures.

The pre-1995 data were rounded to the nearest 100 pCi/L, which damped out variances in the data. The post-1995 RadNet data, where rounding was not applied, exhibit much more scatter, and similar to the GNIP data, the vast majority of the data were less than 100 pCi/L.

CRA constructed a non-parametric upper tolerance limit with a confidence of 95 percent and a coverage of 95 percent based on RadNet data for USEPA Region 5 from 2004 to 2005. The resulting upper tolerance limit is 133 pCi/L, which indicates that CRA is 95 percent confident that 95 percent of the ambient precipitation concentration results are less than 133 pCi/L. The statistical confidence, however, must be compared with the limitations of the underlying RadNet data, which does not include the minimum detectable concentration for a majority of the measurements. Some of the RadNet values less than 200 pCi/L may be approximated. Nevertheless, these results show a background contribution for precipitation of up to 133 pCi/L.

7.2.3 SURFACE WATER DATA Tritium concentrations are routinely measured in large surface water bodies, including Lake Michigan and the Mississippi River. Surface water data from the RadNet database for Illinois sampling stations include East Moline (Mississippi River), Moline (Mississippi River), Marseilles (Illinois River), Morris (Illinois River), Oregon (Rock River), and Zion (Lake Michigan). As is the case for the RadNet precipitation data, the pre-September 1995 Illinois surface water data was rounded to the nearest 100 pCi/L, creating a dampening of variances in the data. The post-1995 Illinois surface water data, similar to the post-1995 Midwest precipitation data, were less than 100 pCi/L with the exception of the Moline (Mississippi River) station. Tritium surface water concentrations at this location varied between 100 and 800 pCi/L, which may reflect local natural or anthropogenic inputs.

Recent surface water measurements for tritium sampling locations upstream of the Quad Cities Generating Station show that concentrations in the Mississippi River are consistently less than 200 pCi/L (Exelon, 2005).

045136 (13) Byron Generating Station 45 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 These results indicate that there is a background tritium concentration in surface water that is typically less than 100 pCi/L, but have approached 800 pCi/L in the Mississippi River.

The USEPA RadNet surface water data typically has a reported "Combined Standard Uncertainty" of 35 to 50 pCi/L. According to USEPA, this corresponds to a

+/- 70 to 100 pCi/L 95 percent confidence bound on each given measurement. Therefore, the typical background data provided may be subject to measurement uncertainty of approximately +/- 70 to 100 pCi/L.

7.2.4 DRINKING WATER DATA Tritium concentrations in drinking water from the RadNet database for three Illinois sampling stations (Chicago, Morris, and East Chicago) exhibit similar trends as the precipitation and surface water data. As with the precipitation and surface water data, the pre-1995 data has dampened out variances due to rounding the data to the nearest 100 pCi/L. The post-1995 results show tritium concentrations in drinking water well less than 100 pCi/L and the tritium concentrations found in precipitation and surface water.

7.2.5 EXPECTED TRITIUM BACKGROUND FOR THE STATION As reported in the GNIP and RadNet databases, tritium concentrations in U.S. Midwest precipitation have typically been less than 100 pCi/L since 1980. Tritium concentrations reported in the RadNet database for Illinois surface water and groundwater, at least since 1995, have typically been less than 100 pCi/L. Based on the USEPA Region 5's 2004 to 2005 RadNet precipitation data, 95 percent of the ambient concentrations of tritiated water in Illinois are expected to be less than 133 pCi/L, based on a 95 percent confidence limit. Tritium concentrations in surface water and drinking water are expected to be comparable or less based on historical data and trends.

Concentrations in groundwater similar to surface water and drinking water are expected to be less as compared to precipitation values. The lower groundwater concentrations are related to the age of the groundwater as compared to the half-life of tritium. Deep aquifers in proximity to crystalline basement rock, however, potentially can also show elevated concentrations of tritium due to lithogenic sources.

045136 (13) Byron Generating Station 46 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 As was noted in Section 7.0, the analytical laboratory is reporting tritium results to a LLD of 200 pCi/L. This concentration also represents a reasonable representation of background groundwater quality, given the data for precipitation, surface water, and drinking water.

Based on the evaluation presented above, the background concentration for tritium at the Station is reasonably represented by the LLD of 200 pCi/L.

7.3 IDENTIFICATION OF POTENTIAL EXPOSURE PATHWAYS AND POTENTIAL RECEPTORS Three potential exposure pathways were considered during the evaluation of tritium in groundwater:

potential groundwater migration to the Station's potable water supply well;

potential groundwater migration off the Station property to private water supply wells; and

potential groundwater migration off the Station property to a surface water body.

The following section provides an overview of each of these three potential exposure pathways for tritium in groundwater.

7.3.1 POTENTIAL GROUNDWATER MIGRATION TO DRINKING WATER USERS AT THE STATION PROPERTY At the Station, the tritium detected in groundwater samples has been isolated to the Galena-Platteville aquifer, which is isolated from the deeper regional groundwater aquifer by the semi-confining Glenwood Formation. Groundwater quality data from production wells and monitoring wells at the Station located below this aquitard do not indicate concentrations of tritium greater than the LLD of 200 pCi/L. As such, the tritium impact is limited to the Galena-Platteville aquifer. There are no water supply wells located on the Station property that draw water from the Galena-Platteville aquifer. The Station receives its potable water from two cased 1,500-foot bedrock wells on the Site, which are installed in the Ironton-Galesville Sandstone. The vertical movement of tritiated water from the Galena-Platteville aquifer into deeper formations is restricted by the semi-confining Glenwood Formation. Since vertical migration of tritiated water through the Glenwood Formation to the Ironton-Galesville Aquifer is 045136 (13) Byron Generating Station 47 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 restricted but theoretically not eliminated, this is a potentially complete exposure pathway but there is no current risk for groundwater ingestion at the Station.

7.3.2 POTENTIAL GROUNDWATER MIGRATION TO DRINKING WATER USERS OFF THE STATION PROPERTY Based on the results of the investigations and the conceptual model, the only potentially complete exposure route (pathway) for tritiated water at the Station is ingestion of the groundwater at nearby private water supply wells. However, due to low permeabilities of the limestones and dolomites of the Galena-Platteville aquifer, along with the general hardness of the water, this aquifer is typically not used for potable water in the area.

The St. Peter Sandstone is the primary source for potable water in the area. The St. Peter Sandstone aquifer is separated from the Galena-Platteville aquifer by a low permeability shale of the Glenwood Formation. Residential water wells that are both off the Station property and in the direction of groundwater flow downgradient from the blowdown line typically obtain water from the St. Peter Sandstone aquifer. These water wells were sampled and were not impacted. In addition, none of the groundwater samples collected from monitoring wells near the property line contained tritium at concentrations greater than the LLD of 200 pCi/L. Therefore, although there is a potentially complete exposure pathway, there is no current risk of exposure associated with groundwater ingestion off the Station property.

7.3.3 POTENTIAL GROUNDWATER MIGRATION TO SURFACE WATER USERS Groundwater does not discharge to the local surface water drainages (ephemeral creeks) and the nearest wells located adjacent to the Rock River have not contained tritium.

There is no potentially complete exposure pathway, therefore there is no current risk of exposure associated with groundwater migration to surface water at the Station.

7.4

SUMMARY

OF POTENTIAL TRITIUM EXPOSURE PATHWAYS There are three potential exposure pathways for tritium at the Station:

potential groundwater migration to the Station's potable supply well; 045136 (13) Byron Generating Station 48 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

potential groundwater migration off the Station property to private water supply wells; and

potential groundwater migration off the Station property to a surface water body.

Based upon the groundwater and surface water data provided and referenced in this investigation, none of the potential receptors are at risk of exposure to concentrations of tritium in excess of the USEPA drinking water standard (20,000 pCi/L).

7.5 OTHER RADIONUCLIDES Target radionuclides were not detected at concentrations greater than the LLDs in the groundwater samples collected. Other non-targeted radionuclides were also included in the tables but excluded from discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

045136 (13) Byron Generating Station 49 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

8.0 CONCLUSION

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

Groundwater Flow

There are two groundwater aquifers within the first 230 feet beneath the Station: the Galena-Platteville aquifer (upper aquifer) and the St. Peter Sandstone aquifer (lower aquifer).

The two aquifers are separated by a semi-confining shale layer of the Glenwood Formation and, therefore, not hydraulically connected under the Station.

Groundwater (the water table) is first encountered in the upper fractured portions of the Galena-Platteville aquifer. Near the Rock River, the bedrock has been eroded, and the water table is in unconsolidated alluvial material.

The general direction of groundwater flow in both aquifers is to the west toward the Rock River.

The groundwater flows radially away from the facility.

The horizontal gradient in the Galena-Platteville aquifer is shallow. There is a slight downward vertical gradient between the upper portion and bottom of the Galena-Platteville aquifer.

Groundwater Quality

Tritium concentrations in groundwater were not detected at concentrations greater than the USEPA drinking water standard of 20,000 pCi/L.

Tritium was not detected at concentrations greater than the LLD of 200 pCi/L in samples collected from the five monitoring wells located in the PA.

Tritium was not detected at concentrations greater than the LLD of 200 pCi/L in 35 of the 39 groundwater samples collected. Concentrations of tritium in the four remaining samples, all collected near vacuum breakers, ranged between 234 +/- 128 pCi/L to 3,260 +/- 367 pCi/L.

Gamma-emitting radionuclides associated with licensed plant operations were not detected at concentrations greater than their respective LLDs in any of the most recent water samples collected as part of this investigation.

Strontium-89/90 was not detected at concentrations greater than the LLD of 2 pCi/L in any sample collected as part of this investigation.

045136 (13) Byron Generating Station 50 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

Tritium was not detected at concentrations greater than the LLD of 200 pCi/L in the water samples collected from the residential water wells.

The HIR data indicate that tritium is not migrating off the Station property.

AFE-Byron Former Fiberglass Blowdown Line

Gamma-emitting radionuclides associated with licensed plant operations were not detected at concentrations greater than their respective LLDs in any of the 13 groundwater samples collected from the four monitoring wells in the vicinity of AFE-Byron-1.

Strontium-89/90 was not detected at a concentration greater than the LLD of 2 pCi/L in any of the 13 groundwater samples collected from the four monitoring wells in the vicinity of AFE-Byron-1.

Tritium was not detected at concentrations greater than the LLD of 200 pCi/L in any of the groundwater samples collected from the four monitoring wells in the vicinity of AFE-Byron-1.

There is no current impact from this AFE to groundwater.

AFE-Byron Vacuum Breaker Vaults

Gamma-emitting radionuclides associated with licensed plant operations were not detected at concentrations greater than their respective LLDs in any of the groundwater samples most recently collected from monitoring wells near AFE-Byron-2.

Strontium-89/90 was not detected at a concentration greater than the LLD of 2 pCi/L in any of the groundwater samples collected from monitoring wells near AFE-Byron-2.

To the west of the generating facility, near the blowdown line, the concentrations of tritium were greater than the LLD of 200 pCi/L in four monitoring wells: AR-2, AR-3, AR-4, and AR-11. These four wells are adjacent to three vacuum breaker vaults: VB-2, VB-3, and VB-4. These vaults formerly contained water with elevated concentrations of tritium.

Two areas where tritium was found in the groundwater near VB-2 and VB-3 are limited to the shallow portions of the Galena-Platteville aquifer.

Near VB-4, the groundwater contains tritium down to the bottom of the Galena-Platteville aquifer.

045136 (13) Byron Generating Station 51 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

The source of the tritium concentrations in the groundwater was periodic leaks during re-seating of the blowdown line vacuum breaker valves.

None of the tritium concentrations detected in the groundwater exceed the USEPA drinking water standard of 20,000 pCi/L.

The shale unit of the Glenwood Formation has a low permeability and acts as a barrier to further downward migration of impacted water down to the St. Peter Sandstone aquifer. Due to the low permeabilities of the Galena-Platteville limestones/dolomites combined with the shallow gradient of the water table, the tritiated water in the Galena-Platteville aquifer will not migrate very far laterally from the VB-2, VB-3, and VB-4 areas.

Tritiated groundwater at the Station is isolated in three areas, and the evidence indicates that it is not migrating off Station property. This is based upon the inferred slow groundwater flow velocities and that groundwater sampling results indicate that monitoring wells outside of these three areas are not impacted. The unimpacted wells include: monitoring wells located hydraulically downgradient, monitoring wells located at the property line, and residential water wells. The tritium detected in groundwater is not the result of large failures of the blowdown line, but of minor failures of the vacuum breaker valves to re-seat during blowdown line discharge events. No knowledge or evidence of large failures of or releases from the blowdown line have been documented or identified through the investigations.

Therefore, additional plume delineation activities or groundwater remediation are not warranted.

AFE-Byron-3 -Protected Area

Groundwater under the PA flows radially outward due to the topographic high on which the PA was constructed. The downgradient locations of the monitoring wells were selected based on this radial groundwater flow pattern. These monitoring wells are situated to provide for an adequate indication for future leak detection.

Tritium was not detected at concentrations greater than the LLD of 200 pCi/L in any of the groundwater samples collected from seven monitoring wells in the vicinity of AFE-Byron-3.

Gamma-emitting radionuclides associated with licensed plant operations were not detected at concentrations greater than their respective LLDs in any of the groundwater samples most recently collected from seven monitoring wells in the vicinity of AFE-Byron-3.

045136 (13) Byron Generating Station 52 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

Strontium-89/90 was not detected at a concentration greater than the LLD of 2 pCi/L in any of the groundwater samples collected from monitoring wells in the vicinity of AFE-Byron-3.

There is no current impact from this AFE to groundwater.

Potential Receptors

Based on the results of this investigation 1 , there is no current risk from exposure to radionuclides associated with licensed plant operations through any of the identified potential exposure pathways.

General Conclusions

Based on the results of this investigation, tritium is not migrating off the Station property at detectable concentrations.

Based on the results of this investigation, there are no known active releases into the groundwater at the Station.

1 Using the LLD specified in this HIR.

045136 (13) Byron Generating Station 53 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 9.0 RECOMMENDATIONS The following presents CRA's recommendations for proposed activities to be completed at the Byron Station.

9.1 DATA GAPS Based on the results of this hydrogeologic investigation, there are no data gaps remaining to support CRAs conclusions regarding the characterization of the groundwater regime and potential impacts from radionuclides at the Station.

9.2 GROUNDWATER MONITORING Based upon the information collected to date, CRA recommends that Exelon conduct periodic monitoring of selected groundwater monitoring well locations.

045136 (13) Byron Generating Station 54 CONESTOGA-ROVERS & ASSOCIATES

Revision 1

10.0 REFERENCES

The materials referenced in the generation of this HIR include:

Byron Station Radiological Environmental Monitoring Program (REMP) Reports.

Byron Station Radiological Effluent Tracking Statistics (RETS) Reports from 1984 to 2005.

Byron Station Updated Final Safety Analysis Report (UFSAR), Rev. #10, December 2004.

Conestoga-Rovers & Associates, June 2001. "Remedial Design Work Plan - Byron Salvage Yard".

Conestoga-Rovers & Associates, May 2006. "Hydrogeologic Investigation Work Plan -

Fleetwide Tritium Assessment - Byron Generating Station".

Exelon Generation Company, May 2005. "Quad Cities Nuclear Power Station, 2004 Annual Radiological Environmental Operating Report", Exelon, Cordoa, Illinois.

Kay, Robert T., Douglas J. Yeskis, William J. Bolen, James R. Rauman, and Scott T. Prinos, 1997. Geology, Hydrology, and Ground-Water Quality at the Byron Superfund Site Near Byron, Illinois, United States Geological Survey, Water-Resources Investigations Report 95-4240, Prepared in Cooperation with the U.S. Environmental Protection Agency Ogle County, 2006, Geographical Information System (GIS) database, http://www.Oglecountygis.org.

Puls, R.W., and M.J. Barcelona, April 1996. Low-Flow (Minimal Drawdown)

Ground-Water Sampling Procedures, EPA Ground Water Issue, EPA/540/S-92/005, R. S. Kerr Environmental Research Center, United States Environmental Protection Agency, Ada, Oklahoma.

RETEC Group, Inc., September 23, 2005. "Residential Well Survey".

United States Department of Agriculture, 2006. Natural Resources Conservation Service website, http.//www.nrcs.usda.gov.

The main references cited in the UFSAR related to this HIR include:

Bradbury, J.C. and Atherton, E., 1965. The Precambrian Basement of Illinois, Circular 382, Illinois State Geological Survey.

Buschbach, T.C., 1964. Cambrian and Ordovician Strata of Northeastern Illinois, Illinois State Geological Survey, Report of Investigation 218, 90 p.

Frye, J.C., et al., 1969. Glacial Tills of Northwestern Illinois, Illinois State Geological Survey, Cir. 437, 45 p.

Willman, H.B., et al., 1967. Geological Map of Illinois, Illinois State Geological Survey.

045136 (13) Byron Generating Station 55 CONESTOGA-ROVERS & ASSOCIATES

Revision 1 Willman, H.B., et al., 1975. Handbook of Illinois Stratigraphy, Bulletin 95, Illinois State Geological Survey.

Willman, H.B. and Frye, J.C., 1970. Pleistocene Stratigraphy of Illinois, Bulletin 94, Illinois State Geological Survey.

045136 (13) Byron Generating Station 56 CONESTOGA-ROVERS & ASSOCIATES

0 2000 4000ft STATION SOURCE: USGS QUADRANGLE MAP; STILLMAN VALLEY, ILLINOIS (1976)

OREGON, ILLINOIS (1983) figure 1.1 STATION LOCATION MAP BYRON GENERATING STATION EXELON GENERATION COMPANY, LLC 45136-21(013)GN-WA001 JUL 13/2006

figure 2.1 LOCAL GEOLOGIC CROSS-SECTIONS A-A' AND B-B' BYRON GENERATING STATION EXELON GENERATION COMPANY, LLC 45136-21(013)GN-WA009 JUL 13/2006

figure 2.2 LOCAL GEOLOGIC CROSS-SECTION C-C' BYRON GENERATING STATION EXELON GENERATION COMPANY, LLC 45136-21(013)GN-WA009 JUL 13/2006

AR-4 (4080 pCi/L - APRIL 26, 2006)

DATE SAMPLE COLLECTED TRITIUM CONCENTRATION X1 X1' WEST EAST AR-2 (527 pCi/L - APRIL 3, 2006)

AR-3 (489 pCi/L - APRIL 3, 2006) 900 900 880 880 AR-11 (2340 pCi/L - APRIL 26, 2006)

VB-2 VB-3 MW-2 MW-1 MW-3 860 860 AR-4 (4080 pCi/L - APRIL 26, 2006)

DF-5S 840 VB-4 840 PC-6B DF-6 PC-3B 820 820 VB-5 799.77 799.63 AR-5 800 798.50 800 796.87 VB-6 787.51 AR-6 780 780 CAR-2 760.58 ELEVATION (ft. AMSL) ELEVATION (ft. AMSL) 760 760 742.74 743.18 742.41 740 739.29 740 736.89 PROPERTY BOUNDARY 720 720 TW-14 ROAD CAR-1 700 700 688.08 684.22 680 680 675.00 672 672.63 672.93 660 660 SCALE VERIFICATION THIS BAR MEASURES 1" ON ORIGINAL. ADJUST SCALE ACCORDINGLY.

640 640 620 620 EXELON GENERATION COMPANY, LLC FLEETWIDE ASSESSMENT 600 600 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 HYDROGEOLOGIC CROSS-SECTION X1-X1' BYRON GENERATING STATION DISTANCE (ft.) BYRON, ILLINOIS Source

Reference:

Project Manager: Reviewed By: Date:

S. QUIGLEY M. KELLY JULY 2006 Scale: Project N o : Report N o : Drawing N o :

AS SHOWN 45136-21 013 figure 5.2 45136-21(013)GN-WA010 JUL 13/2006

AR-4 (4080 pCi/L - APRIL 26, 2006)

DATE SAMPLE COLLECTED TRITIUM CONCENTRATION X2 SOUTH 900 880 AR-11 (2340 pCi/L - APRIL 26, 2006) 860 AR-4 (4080 pCi/L - APRIL 26, 2006) 840 MW-41 DF-24 820 800 PC-1B/DF-8/PC-1C 780 MW-30/DF-23 ELEVATION (ft. AMSL) 760 745.49 742.41 742.74 740 723.79 720.26 717.17 720 718.01 717.60 700 679.53 680 660 SCALE VERIFICATION THIS BAR MEASURES 1" ON ORIGINAL. ADJUST SCALE ACCORDINGLY.

640 620 EXELON GENERATION COMPANY, LLC FLEETWIDE ASSESSMENT 600 0 500 1000 1500 2000 2500 3000 HYDROGEOLOGIC CROSS-SECTION X2-X2' BYRON GENERATING STATION DISTANCE (ft.) BYRON, ILLINOIS Source

Reference:

Project Manager: Reviewed By: Date:

S. QUIGLEY M. KELLY JULY 2006 Scale: Project N o : Report N o : Drawing N o :

AS SHOWN 45136-21 013 figure 5.3 45136-21(013)GN-CO002 JUL 13/2006

AR-4 X3 X3' X3 X3

WEST NORTHEAST WEST SOUTHEAST CIRCULATING WATER 900 900 900 900 AUXILIARY BUILDING TURBINE BUILDING SERVICE BUILDING AUXILIARY BUILDING TURBINE BUILDING PUMP HOUSE CONSTRUCTION AR-9 UNIT #2 UNIT #2 FLUME 880 880 880 880 AR-7 AR-7 RUN-OFF POND AR-10 860 860 860 860 840 837.66 840 840 840 ELEVATION (ft. AMSL) ELEVATION (ft. AMSL) ELEVATION (ft. AMSL) ELEVATION (ft. AMSL) 820 820 820 817.27 820 800 800 800 800 780 780 780 780 766.74 766.74 760 760 760 760 740 740 740 740 720 720 720 720 0 500 1000 1500 2000 0 500 1000 1500 2000 DISTANCE (ft.) DISTANCE (ft.)

SCALE VERIFICATION THIS BAR MEASURES 1" ON ORIGINAL. ADJUST SCALE ACCORDINGLY.

EXELON GENERATION COMPANY, LLC FLEETWIDE ASSESSMENT HYDROGEOLOGIC CROSS-SECTION X3-X3' AND X3-X3

BYRON GENERATING STATION BYRON, ILLINOIS Source

Reference:

Project Manager: Reviewed By: Date:

S. QUIGLEY M. KELLY JULY 2006 Scale: Project N o : Report N o : Drawing N o :

AS SHOWN 45136-21 013 figure 5.4 45136-21(013)GN-CO003 AUG 18/2006

TABLE 2.1 Page 1 of 3

SUMMARY

OF EXISTING WELL INFORMATION FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Surface Reference Screened Interval Hydrogeologic X coor. Y coor. Elevation Elevation Top Bottom Top Bottom Middle Well Unit Sample Location (State Plane Coordinates) (ft AMSL) 2 (ft AMSL) (ft bgs) 3 (ft AMSL) Construction Screened 1 Exelon-Owned Wells Previously Existing Water Wells GW-9 4 2532455.60 1972488.60 841.51 841.73 NA 5 NA -- -- -- 6-inch open hole GPWT Well 7 4 2538213.33 1969732.76 891.17 891.24 NA NA -- -- -- 6-inch open hole GPWT Deep Well 1 2537066.85 1970148.36 NA NA NA ~ 1500 -- -- -- 12 to 15-inch open hole NA Deep Well 2 2535936.76 1969964.84 NA NA NA ~ 1500 -- -- -- 12 to 15-inch open hole NA Monitoring Wells Installed During the Blowdown Line Investigation AR-1 2536048.98 1972460.65 868.11 871.10 50 70 818.11 798.11 808.11 2-inch PVC screen GPWT AR-2 2534570.16 1973401.77 864.37 867.38 71 81 793.37 783.37 788.37 2-inch PVC screen GPWT AR-3 2533354.08 1973345.67 857.76 860.64 60 70 797.76 787.76 792.76 2-inch PVC screen GPWT AR-4 2530325.59 1974343.03 830.23 832.74 99.5 119.5 730.73 710.73 720.73 2-inch PVC screen GPWT AR-5 2526970.90 1974279.73 793.27 795.75 102 122 691.27 671.27 681.27 2-inch PVC screen GPWT AR-6 2526375.64 1974201.54 782.22 784.55 95 115 687.22 667.22 677.22 2-inch PVC screen GPWT AR-7 2536172.26 1970914.51 868.99 871.28 102 112 766.99 756.99 761.99 2-inch PVC screen GPWT AR-8 2536591.62 1970080.22 869.71 872.11 30 50 839.71 819.71 829.71 2-inch PVC screen GPWT AR-9 2537777.21 1970783.66 873.77 876.77 55.5 65.5 818.27 808.27 813.27 2-inch PVC screen GPWT AR-10 2537573.15 1971916.71 856.65 859.15 19 29 837.65 827.65 832.65 2-inch PVC screen GPWT AR-11 2530300.13 1974330.58 829.35 831.65 139.5 149.5 689.85 679.85 684.85 2-inch PVC screen BGP CAR-1 2525447.90 1974018.64 692.25 694.87 45 55 647.25 637.25 642.25 2-inch PVC screen UAWT CAR-2 2529246.47 1974300.12 769.40 772.01 25 35 744.40 734.40 739.40 2-inch PVC screen GPWT CAR-3 2537064.71 1970545.52 869.11 872.16 43 63 826.11 806.11 816.11 2-inch PVC screen GPWT TW-1 2536119.01 1972474.04 868.81 870.70 3.5 8.5 865.31 860.31 862.81 2-inch PVC screen Shallow Overburden TW-2 2536137.15 1972477.09 869.11 870.73 2 7 867.11 862.11 864.61 2-inch PVC screen Shallow Overburden TW-3 2534676.01 1973300.70 866.92 868.35 5.5 10.5 861.42 856.42 858.92 2-inch PVC screen Shallow Overburden TW-4 2534674.53 1973321.59 866.53 869.48 5.5 10.5 861.03 856.03 858.53 2-inch PVC screen Shallow Overburden TW-5 2533371.75 1973305.18 858.37 860.78 3 8 855.37 850.37 852.87 2-inch PVC screen Shallow Overburden TW-6 2533370.28 1973323.29 858.07 859.93 3.5 8.5 854.57 849.57 852.07 2-inch PVC screen Shallow Overburden TW-7 2530360.35 1974366.22 830.91 832.25 6 11 824.91 819.91 822.41 2-inch PVC screen Shallow Overburden TW-8 2530358.62 1974386.10 830.10 831.67 7 12 823.10 818.10 820.60 2-inch PVC screen Shallow Overburden TW-9 2527013.94 1974272.31 793.82 796.42 3 8 790.82 785.82 788.32 2-inch PVC screen Shallow Overburden TW-10 2527013.99 1974256.60 793.70 795.88 2.5 7.5 791.20 786.20 788.70 2-inch PVC screen Shallow Overburden TW-11 2526439.04 1974253.50 782.38 785.16 5 10 777.38 772.38 774.88 2-inch PVC screen Shallow Overburden TW-12 2526438.39 1974235.97 783.38 785.32 7 12 776.38 771.38 773.88 2-inch PVC screen Shallow Overburden TW-13 2525412.16 1974276.44 698.03 700.47 13 18 685.03 680.03 682.53 2-inch PVC screen Shallow Overburden CRA 045136 (13) Byron Generating Station

TABLE 2.1 Page 2 of 3

SUMMARY

OF EXISTING WELL INFORMATION FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Surface Reference Screened Interval Hydrogeologic X coor. Y coor. Elevation Elevation Top Bottom Top Bottom Middle Well Unit Sample Location (State Plane Coordinates) (ft AMSL) 2 (ft AMSL) (ft bgs) 3 (ft AMSL) Construction Screened 1 TW-14 2525537.43 1974058.60 697.40 699.41 24 34 673.40 663.40 668.40 2-inch PVC screen Shallow Overburden TW-15 2525587.27 1973925.58 694.32 695.73 24 29 670.32 665.32 667.82 2-inch PVC screen Shallow Overburden Byron Salvage PRP Group-Owned Monitoring Wells DF-1S 2531216.65 1973682.92 785.49 786.89 44 59 741.49 726.49 733.99 2-inch stainless steel screen GPWT DF-1D 2531226.90 1973676.38 786.32 787.48 79 84 707.32 702.32 704.82 2-inch stainless steel screen BGP DF-2S 2531242.96 1973864.59 794.44 794.96 59 74 735.44 720.44 727.94 2-inch stainless steel screen GPWT DF-3S 2531570.17 1973536.07 790.26 791.82 51 66 739.26 724.26 731.76 2-inch stainless steel screen GPWT DF-4DS 2532386.02 1973588.26 831.41 832.98 46 61 785.41 770.41 777.91 2-inch stainless steel screen GPWT DF-4DD 2532385.52 1973588.31 NA 832.79 144 149 -- -- -- 2-inch stainless steel screen BGP DF-5S 2532646.87 1973412.71 843.19 844.12 13 65 830.19 778.19 804.19 6-inch open hole GPWT DF-6 2531991.61 1973735.68 826.31 827.89 118 123 708.31 703.31 705.81 2-inch stainless steel screen BGP DF-7S 2527903.67 1975299.65 709.98 712.38 22 27 687.98 682.98 685.48 2-inch stainless steel screen UAWT DF-7D 2527898.09 1975298.28 709.67 712.55 43 48 666.67 661.67 664.17 2-inch stainless steel screen UAM DF-8 2530141.74 1973270.87 755.05 757.47 58 63 697.05 692.05 694.55 2-inch stainless steel screen BGP DF-10 2532417.79 1974527.51 833.04 834.01 69 84 764.04 749.04 756.54 2-inch stainless steel screen GPWT DF-11 2532534.02 1974574.44 833.05 834.21 68 83 765.05 750.05 757.55 2-inch stainless steel screen GPWT DF-12 2532609.19 1974523.28 831.43 834.48 127 132 704.43 699.43 701.93 2-inch stainless steel screen BGP DF-13 2532200.73 1973830.53 836.33 838.84 106 111 730.33 725.33 727.83 2-inch stainless steel screen MGP DF-15 2532645.11 1972942.97 846.50 847.79 7 115 839.50 731.50 785.50 6-inch open hole GPWT DF-17 2531725.46 1972911.91 817.65 820.14 115 120 702.65 697.65 700.15 2-inch stainless steel screen BGP DF-18 2531124.33 1973590.07 777.77 780.28 45 60 732.77 717.77 725.27 2-inch stainless steel screen GPWT DF-19 2531143.77 1973770.63 786.13 788.53 55 65 731.13 721.13 726.13 2-inch stainless steel screen GPWT DF-22S 2531524.65 1972931.42 808.73 811.85 76 86 732.73 722.73 727.73 2-inch stainless steel screen GPWT DF-22D 2531524.95 1972931.41 808.73 811.56 101 106 707.73 702.73 705.23 2-inch stainless steel screen BGP DF-23 2530101.41 1972863.81 752.57 755.39 60 65 692.57 687.57 690.07 2-inch stainless steel screen BGP DF-24 2530081.29 1974051.80 812.28 813.68 19 102 793.28 710.28 751.78 6-inch open hole GPWT DF-25 2530981.83 1973779.38 785.15 786.36 NA NA -- -- -- -- NA MW-1 2534233.15 1973475.34 859.96 861.77 13 71 846.96 788.96 817.96 4-inch open hole GPWT MW-2 2534208.57 1973479.15 860.08 861.07 225 230 635.08 630.08 632.58 2-inch stainless steel screen SS MW-3 2533174.54 1973415.41 855.90 858.6 14 76 841.90 779.90 810.90 4-inch open hole GPWT CRA 045136 (13) Byron Generating Station

TABLE 2.1 Page 3 of 3

SUMMARY

OF EXISTING WELL INFORMATION FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Surface Reference Screened Interval Hydrogeologic X coor. Y coor. Elevation Elevation Top Bottom Top Bottom Middle Well Unit Sample Location (State Plane Coordinates) (ft AMSL) 2 (ft AMSL) (ft bgs) 3 (ft AMSL) Construction Screened 1 MW-15 2532472.31 1974788.27 821.22 822.23 75 86 746.22 735.22 740.72 2-inch stainless steel screen GPWT MW-16 2532464.57 1974786.05 821.29 823.47 109 120 712.29 701.29 706.79 2-inch stainless steel screen BGP MW-20R 2532466.05 1974790.91 820.57 821.85 181 191 639.57 629.57 634.57 2-inch stainless steel screen SS MW-21 2532458.60 1974791.94 820.42 821.63 224 234 596.42 586.42 591.42 2-inch stainless steel screen SS MW-30 2530196.65 1972880.11 754.70 758.68 27 37 727.70 717.70 722.70 2-inch stainless steel screen GPWT MW-36 2532608.79 1973569.23 841.60 843.73 146 156 695.60 685.60 690.60 2-inch stainless steel screen BGP MW-37 2532608.88 1973558.19 841.16 843.33 192 202 649.16 639.16 644.16 2-inch stainless steel screen SS MW-39 2532616.75 1974389.87 834.18 836.67 175 185 659.18 649.18 654.18 2-inch stainless steel screen SS MW-41 2531156.40 1975401.53 814.46 816.87 111 121 703.46 693.46 698.46 2-inch stainless steel screen BGP MW-42 2532613.32 1974380.69 834.21 836.31 141 151 693.21 683.21 688.21 2-inch stainless steel screen BGP PC-1B 2530160.35 1973268.15 755.49 757.28 36 46 719.49 709.49 714.49 2-inch stainless steel screen GPWT PC-1C 2530162.01 1973286.18 755.80 757.89 101 111 654.80 644.80 649.80 2-inch stainless steel screen SS PC-2B 2532010.43 1974162.53 840.43 842.54 85 103 755.43 737.43 746.43 2-inch stainless steel screen GPWT PC-3B 2532010.72 1973717.55 826.58 828.3 67 78 759.58 748.58 754.08 2-inch stainless steel screen GPWT PC-4B 2531377.35 1973122.19 800.53 802.8 71 81 729.53 719.53 724.53 2-inch stainless steel screen GPWT PC-5B 2530689.47 1973701.97 786.26 788.35 62 72 724.26 714.26 719.26 2-inch stainless steel screen GPWT PC-6B 2531016.38 1974314.45 828.85 831.01 86 96 742.85 732.85 737.85 2-inch stainless steel screen GPWT Notes:

1 Hydrogeologic unit screened: GPWT, well open to the water table in the Galena-Platteville aquifer BGP, well open to the base of the Galena-Platteville aquifer MGP, well open to the middle of the Galena-Platteville aquifer UAWT, well open to the water table in the unconsolidated aquifer UAM, well open to the middle of the unconsolidated aquifer SS, well open to the St. Peter Sandstone aquifer 2

ft AMSL - feet Above Mean Sea Level 3

ft bgs - feet below ground surface 4

The tops of the wells for GW-9 and Well 7 are located underground within concrete vaults. The surveyed reference elevation is actually the top of the metal rim of the concrete vault at the ground surface.

5 NA - not available CRA 045136 (13) Byron Generating Station

TABLE 4.1 Page 1 of 2

SUMMARY

OF MONITORING WELL DEVELOPMENT - BLOWDOWN LINE INVESTIGATION FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Volume Location Date Purged pH Conductivity Temperature Observations 1

(gallons) (Std. Units) (µS/cm) 2 (°C) 3 AR-1 3/23/06 100 NR 4 NR NR NR AR-2 3/21/06 100 NR NR NR NR AR-3 3/22/06 75 NR NR NR NR AR-4 3/27/06 NR 7.04 1,300 12.5 Murky NR 7.47 1,405 12.8 Murky 15 7.32 863 12.6 Murky AR-5 03/23/06 7 NR NR NR NR AR-6 3/22/06 1.5 NR NR NR Misty, turbid 3/23/06 5 NR NR NR NR 7 7.79 637 10.4 Murky 9 8.01 638 10.3 Murky Well going dry AR-7 3/28/06 50 NR NR NR NR AR-8 3/31/06 10 NR NR NR NR AR-9 4/4/06 12 NR NR NR NR AR-10 4/5/06 25 NR NR NR NR AR-11 4/11/06 Development conducted by the drilling company.

CAR-1 3/22/06 100 7.43 577 11.1 Clear 105 7.44 577 11.2 Clear CAR-2 3/22/06 7 NR NR NR NR Well runs dry CAR-3 3/29/06 40 NR NR NR NR Well runs dry 45 NR NR NR NR Well runs dry TW-13 3/7/06 8 7.41 743 10.7 Cloudy, light brown 10 7.45 744 10.5 Cloudy, light brown 12 7.42 744 10.7 Cloudy, light brown CRA 045136 (13) Byron Generating Station

TABLE 4.1 Page 2 of 2

SUMMARY

OF MONITORING WELL DEVELOPMENT - BLOWDOWN LINE INVESTIGATION FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Volume Location Date Purged pH Conductivity Temperature Observations 1

(gallons) (Std. Units) (µS/cm) 2 (°C) 3 TW-14 3/7/06 Well is dry -- -- -- --

4/5/06 75 NR NR NR Clear TW-15 3/7/06 1.0 NR NR NR Light brown Well runs dry 1.3 NR NR NR NR Well runs dry 6.3 7.54 737 9.7 Cloudy 11.3 7.62 704 10.6 Cloudy 16.3 7.57 689 10.6 Cloudy Notes:

1 Std. Units - standard units 2

µS/cm - microSiemens per centimeter 3

degrees Celsius 4

NR - Not Reported CRA 045136 (13) Byron Generating Station

TABLE 4.2 Page 1 of 2

SUMMARY

OF GROUNDWATER ELEVATIONS - MARCH/APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS March 23, 2006 April 4, 2006 Sample Reference Depth to Groundwater Depth to Groundwater Location Elevation Water Elevation Water Elevation (ft AMSL) (1) (feet below Reference) (feet AMSL) (feet below Reference) (feet AMSL)

AR-1 871.10 39.70 831.40 39.72 831.38 AR-2 864.37 65.69 798.68 66.06 798.31 AR-3 857.76 59.60 798.16 60.27 797.49 AR-5 793.27 105.37 687.90 104.21 689.06 AR-6 782.22 107.75 674.47 107.54 674.68 AR-7 868.99 -- -- 103.02 765.96 AR-8 869.71 -- -- 53.57 816.14 CAR-1 692.25 20.03 672.22 20.06 672.20 CAR-2 769.40 32.90 736.50 26.84 742.56 CAR-3 869.11 -- -- 44.49 824.62 DF-12 834.48 90.13 744.35 -- --

DF-13 838.84 94.45 744.39 94.16 744.68 DF-15 847.79 102.30 745.49 107.32 740.47 DF-17 820.14 91.00 729.14 90.87 729.27 DF-18 780.28 55.60 724.68 55.48 724.80 DF-19 788.53 64.02 724.51 63.90 724.63 DF-1D 787.48 62.92 724.56 62.75 724.73 DF-1S 786.89 61.92 724.97 61.80 725.09 DF-22D 811.56 85.78 725.78 -- --

DF-22S 811.85 75.99 735.86 85.86 725.99 DF-23 755.39 28.73 726.66 60.02 695.37 DF-24 813.68 91.28 722.40 91.11 722.57 DF-2S 794.96 69.48 725.48 69.00 725.96 DF-3S 791.82 65.54 726.28 65.46 726.36 DF-4DD 832.79 88.30 744.49 88.01 744.78 DF-6 827.89 90.71 737.18 89.72 738.17 DF-8 757.47 40.57 716.90 40.47 717.00 DF-9S 707.43 21.63 685.80 21.35 686.08 MS-1 728.94 34.91 694.03 35.60 693.34 MS-2 730.86 53.95 676.91 54.08 676.78 MW-1 861.77 61.82 799.95 61.01 800.76 MW-11 747.68 -- -- 34.01 713.67 MW-12I 726.57 21.65 704.92 21.67 704.90 MW-12S 728.15 23.70 704.45 21.86 706.29 MW-15 822.23 78.25 743.98 78.02 744.21 MW-16 823.47 79.54 743.93 79.28 744.19 MW-2 861.07 177.45 683.62 176.89 684.18 MW-20R 821.85 141.20 680.65 141.12 680.73 MW-21 821.63 141.05 680.58 140.93 680.70 MW-30 758.68 38.27 720.41 -- --

MW-36 843.73 99.26 744.47 99.00 744.73 MW-37 843.33 161.72 681.61 161.60 681.73 MW-39 836.67 155.73 680.94 155.61 681.06 MW-41 816.87 73.02 743.85 72.74 744.13 MW-42 836.31 92.17 744.14 91.84 744.47 OS-NW-1D 825.05 148.85 676.20 81.93 743.12 CRA 045136 (13) Byron Generating Station

TABLE 4.2 Page 2 of 2

SUMMARY

OF GROUNDWATER ELEVATIONS - MARCH/APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS March 23, 2006 April 4, 2006 Sample Reference Depth to Groundwater Depth to Groundwater Location Elevation Water Elevation Water Elevation (ft AMSL) (1) (feet below Reference) (feet AMSL) (feet below Reference) (feet AMSL)

OS-NW-1S 825.10 82.50 742.60 50.94 774.16 OS-SW-1 729.34 59.40 669.94 50.91 678.43 OS-SW-2D 734.21 54.45 679.76 54.32 679.89 OS-SW-2I 734.38 54.50 679.88 54.38 680.00 OS-SW-2S 734.26 49.75 684.51 49.20 685.06 OS-SW-3D 799.65 117.13 682.52 140.53 659.12 OS-SW-3S 800.11 104.29 695.82 126.28 673.83 PC-1B 757.28 40.07 717.21 40.03 717.25 PC-1C 757.89 78.90 678.99 78.90 678.99 PC-2B 842.54 -- -- 86.26 756.28 PC-4B 802.80 76.65 726.15 76.53 726.27 PC-5B 788.35 65.44 722.91 65.88 722.47 PC-6B 831.01 81.19 749.82 90.43 740.58 RR-9 688.97 18.05 670.92 17.92 671.05 RR-10 675.83 -- -- 3.66 672.17 Notes:

(1) feet AMSL - feet Above Mean Sea Level CRA 045136 (13) Byron Generating Station

TABLE 4.3 Page 1 of 5

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - MARCH/APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Well Volume Location Date Volume Purged pH Conductivity Temperature Turbidity Observations (gallons) (gallons) (Std. Units) (µS/cm) (1) (°C) (NTU) (2)

AR-1 3/24/06 -- -- 7.79 609 10.3 17 --

-- 7.89 600 10.8 14.6 --

7 7.66 588 11.0 14 --

3/29/06 -- -- 7.82 571 10.6 29.2 --

-- 7.68 572 11.2 12.1 --

-- 7.52 565 11.4 7.9 --

7 7.54 560 11.3 6.2 --

4/6/06 -- 5 7.35 574 11.5 121 --

10 7.39 570 11.6 74 --

15 7.41 568 11.6 47 --

4/12/06 -- -- 8.44 638 14.3 -- Clear to murky

-- 7.89 572 13.3 -- Clear to murky 7 7.79 564 13.4 -- Clear to murky AR-2 3/24/06 -- -- 7.53 806 9.0 216 --

-- 7.53 811 9.9 510 --

2.5 7.78 862 9.8 625 --

3/27/06 2.5 -- 8.39 807 10.3 80.5 --

-- 7.94 792 10.2 65 --

-- 7.78 800 10.6 41.6 --

-- 7.73 812 10.2 40.3 --

3.5 7.69 801 10.1 37.8 --

3/29/06 -- -- 7.93 825 11.2 91.9 --

-- 7.71 830 12.1 82.7 --

-- 7.55 831 11.9 74.5 --

5 7.68 821 11.9 89.3 --

4/3/06 -- -- 7.75 845 13.2 78.9 --

-- 7.67 854 13.3 125 --

5 7.65 870 13.6 127 --

4/10/06 -- -- 7.45 880 12.5 166 --

-- 7.56 857 12.3 135 --

3 7.43 871 13.4 117 --

AR-3 3/24/06 0.2 -- 7.30 735 9.6 300 --

-- 7.17 724 10.6 310 --

5 7.14 732 10.6 315 --

3/27/06 -- -- 7.30 731 10.9 64.9 --

-- 7.19 714 11.1 46.4 --

-- 7.18 722 11.3 25.2 --

-- 7.19 723 11.4 15.3 --

7 -- -- -- 12.5 --

3/29/06 -- -- 7.27 708 11.2 15.05 --

-- 7.28 714 11.2 7.48 --

7 7.21 711 11.5 4.82 --

4/3/06 -- -- 7.40 762 13.1 22 --

-- 7.40 712 11.9 12 --

8 7.43 715 12.2 9.6 --

4/10/06 -- -- 7.26 734 13.8 84.4 --

-- 7.37 728 13.4 78.2 --

8 7.15 726 13.4 75.3 --

AR-4 3/28/06 4.9 -- 7.31 1,220 12.6 560 --

-- 7.31 1,215 13.0 416 --

5 7.41 1,213 12.2 518 --

3/29/06 1.4 -- 7.45 1,169 13.0 116 --

-- 7.22 1,168 13.5 165.2 --

6.5 7.32 1,162 13.3 160.2 --

4/4/06 -- -- 7.16 1,223 11.3 608 --

-- 7.65 1,224 12.3 574 --

10 7.62 1,221 12.3 511 --

4/10/06 -- -- 6.61 1,209 11.3 522 --

-- 6.72 1,148 13.3 439 --

-- 6.85 1,129 14.2 204 --

9.5 7.05 1,160 14.4 336 --

AR-5 3/24/06 -- -- 8.14 998 10.0 908 --

-- 7.86 930 10.1 552 --

CRA 045136 (13) Byron Generating Station

TABLE 4.3 Page 2 of 5

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - MARCH/APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Well Volume Location Date Volume Purged pH Conductivity Temperature Turbidity Observations (gallons) (gallons) (Std. Units) (µS/cm) (1) (°C) (NTU) (2)

-- 7.71 880 10.2 950 --

3/29/06 2.6 -- 7.85 895 10.6 205 --

-- 7.68 888 12.2 160 --

4.5 7.63 892 13.3 163.7 --

4/6/06 -- -- 7.81 1,104 10.4 355 --

-- 7.90 1,025 11.2 313 --

-- 7.81 1,037 11.6 -- --

4/11/06 -- -- 7.20 1,047 12.7 862 --

-- 7.16 1,077 14.5 884 --

4.5 7.18 1,072 14.9 927 --

AR-6 3/24/06 -- -- 7.87 334 9.7 1,041 --

-- 8.06 628 10.0 1,065 --

2.5 7.96 624 10.2 1,030 --

3/29/06 1.3 -- 8.00 635 11.6 1,080 --

-- 7.78 614 11.3 1,182 --

3.5 7.69 616 11.9 1,052 --

4/6/06 -- 3.5 7.92 606 13.7 123 --

4/11/06 -- -- 7.36 629 12.5 430 --

-- 7.36 645 12.5 381 --

-- 7.36 648 12.6 422 --

AR-7 3/30/06 1.5 6.8 7.94 1,100 13.5 >999 --

4/5/06 -- 1 7.98 1,189 12.1 439 --

1.5 7.58 1,168 13.1 420 --

2.5 7.56 1,151 13.4 415 --

4/11/06 1.1 -- 8.08 1,205 14.4 -- Murky

-- 7.78 1,178 13.9 -- Murky 2 7.78 1,160 13.7 -- Murky AR-8 4/5/06 -- 0.5 8.15 522 11.5 343 --

0.75 8.26 509 11.9 400 --

2 8.46 543 11.7 609 --

4/11/06 3.0 -- 8.08 572 12.6 -- --

-- 8.02 571 12.7 -- --

3 8.35 536 12.6 -- --

AR-9 4/5/06 -- 0.75 7.77 985 13.6 452 --

1.25 7.78 989 13.0 470 --

-- 7.69 919 13.1 -- --

4/11/06 1.6 -- 7.61 909 14.6 114 --

-- 7.81 912 13.8 202 --

2.5 7.88 911 13.8 286 --

AR-10 4/6/06 1.6 1.6 7.11 4.64 10.5 624 --

3 7.00 4.28 10.6 711 --

4.5 6.97 4.20 10.6 763 --

4/12/06 1.6 -- 7.22 3,850 11.7 -- Clear to murky

-- 7.08 3,870 11.3 -- Clear to murky 3 7.03 3,800 11.2 -- Clear to murky AR-11 4/18/06 10.1 7.5 Water level dropped to the top of the pump, no readings Clear, no odor 11.5 No readings Clear, no odor CAR-1 3/23/06 5.6 -- 7.08 566 11.0 63 --

-- 7.48 562 11.7 50.2 --

-- 7.45 561 10.9 34 --

3/29/06 -- -- 7.75 565 10.1 405 --

-- 7.63 551 10.4 203 --

-- 7.55 559 10.5 69.7 --

-- 7.54 561 10.5 31.7 --

8 -- -- -- 11.6 --

4/6/06 5.5 20 7.76 547 10.8 72 --

4/12/06 -- -- 7.92 572 13.8 -- Clear to murky

-- 7.97 562 12.7 -- Clear to murky 5 7.90 565 13.0 -- Clear to murky CRA 045136 (13) Byron Generating Station

TABLE 4.3 Page 3 of 5

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - MARCH/APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Well Volume Location Date Volume Purged pH Conductivity Temperature Turbidity Observations (gallons) (gallons) (Std. Units) (µS/cm) (1) (°C) (NTU) (2)

CAR-2 3/24/06 0.6 1 7.11 878 9.8 >999 --

3/29/06 0.4 -- 7.72 809 11.4 1210 --

0.33 7.42 807 11.0 1232 --

4/6/06 1.4 1.5 7.67 800 11.3 >999 --

3 7.60 793 11.1 >999 --

4/12/06 -- -- 7.79 865 12.0 -- --

-- 7.38 864 11.7 -- --

1 7.37 858 12.1 -- --

CAR-3 3/30/06 2.9 3 7.98 920 17.1 >999 --

4/5/06 -- 1.25 7.75 956 16.4 168 --

-- 7.67 947 16.4 144 --

3.5 7.65 957 16.5 108 --

4/11/06 3.1 -- 7.79 933 17.0 -- --

-- 7.89 945 17.1 -- --

4 7.87 949 17.2 -- --

DF-1S 3/30/06 0.25 -- 7.28 823 11.6 170 --

-- 7.27 818 11.1 182 --

1 7.24 815 11.1 161 --

4/6/06 0.24 0.25 7.77 838 8.4 >999 --

0.5 7.71 844 8.4 >999 --

0.75 7.69 846 8.4 >999 --

DF-1D 3/29/06 3.6 -- 7.38 820 12.2 7.65 --

-- 7.38 812 11.9 2.37 --

8.5 7.41 811 11.9 3.62 --

4/6/06 3.5 3.5 6.54 387 9.4 36 --

7 6.50 426 9.5 41 --

10.5 6.40 444 9.5 10 --

DF-2S 3/29/06 1.1 -- 7.87 690 14.8 217 --

-- 7.27 681 13.4 217 --

-- 7.20 684 13.5 217 --

Well dry at slow purge rate 4/6/06 1.2 1 No readings --

Dry at approximately 1.0 gallon DF-3S 3/31/06 0.6 -- 8.16 795 10.8 760 Murky

-- 7.99 793 10.6 683 Murky 2 7.94 793 10.6 694 Murky 4/6/06 0.54 2 No readings --

DF-4DS 3/30/06 0.94 -- 8.05 707 11.9 1415 --

-- 7.93 712 11.1 1398 --

3 7.98 718 11.1 1440 --

4/6/06 0.91 3 7.94 727 11.1 >999 --

DF-6 3/30/06 5.3 -- 7.18 668 14.0 10.55 --

-- 7.21 656 14.6 11.58 --

6 7.26 651 14.1 13.7 --

4/6/06 -- -- 7.27 691 10.9 19.1 --

-- 7.26 670 11.2 20.2 --

10 7.30 656 11.4 23.2 --

DF-12 3/31/06 7.5 -- 7.70 771 11.9 1.47 --

-- 7.35 773 11.6 0.97 --

8.5 7.28 771 11.6 1.07 --

4/6/06 -- -- 7.27 779 11.8 2.08 --

-- 7.26 782 12.1 0.99 --

8.5 7.26 782 12.1 0.82 --

DF-19 3/30/06 0.5 5 7.22 837 11.0 289 --

4/6/06 0.29 3 7.31 848 9.5 61 --

DF-24 3/30/06 -- -- 7.62 850 13.4 49.4 --

-- 7.32 844 13.2 34.9 --

-- 7.27 845 13.2 25.4 --

CRA 045136 (13) Byron Generating Station

TABLE 4.3 Page 4 of 5

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - MARCH/APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Well Volume Location Date Volume Purged pH Conductivity Temperature Turbidity Observations (gallons) (gallons) (Std. Units) (µS/cm) (1) (°C) (NTU) (2) 20 7.29 843 13.2 34.5 --

4/6/06 -- -- 7.22 844 11.3 2.84 --

-- 7.16 846 11.4 0.8 --

22 7.15 848 11.4 0.37 --

GW-9 3/7/06 39 20 7.43 816 12.6 -- Clear, no odor 40 7.42 814 12.6 -- Clear, no odor 60 7.39 811 12.4 -- Clear, no odor MW-1 3/31/06 1.8 -- 7.44 554 10.7 516 --

-- 7.67 542 10.4 600 --

4 7.39 541 10.3 502 --

4/6/06 -- -- 7.73 560 10.4 176 --

7 7.71 559 10.5 160 --

MW-2 3/31/06 6.5 -- 8.39 397 13.9 6.17 --

-- 8.18 543 13.7 15.4 --

15 7.65 563 13.9 5.43 --

4/6/06 -- -- 7.50 589 12.6 3.28 --

-- 7.47 594 12.8 1.70 --

15 7.49 584 12.8 1.28 --

MW-3 3/31/06 1.4 -- 7.67 670 11.7 156 --

-- 7.33 663 11.6 210 --

2.8 7.29 665 11.6 199 --

4/6/06 1.4 6 7.29 644 11.6 142 --

MW-30 3/31/06 0.5 -- 7.60 589 9.8 840 --

-- 7.55 587 10.1 972 --

0.8 7.52 589 10.1 1,024 --

4/6/06 0.4 1 No readings --

MW-36 3/31/06 9.5 -- 7.30 842 12.9 74.9 --

-- 7.28 815 12.1 39.3 --

18 7.32 812 12.6 39.8 --

4/6/06 -- -- 7.15 831 11.9 9.82 --

-- 7.18 833 11.9 8.19 --

12 7.21 831 10.9 6.19 --

MW-37 3/31/06 6.5 -- 7.46 616 15.0 11.8 --

-- 7.41 604 14.6 4.81 --

15 7.38 604 14.4 0.67 --

4/6/06 -- -- 7.21 609 12.5 5.2 --

-- 7.27 609 12.9 2.94 --

8 7.29 615 12.9 2.43 --

MW-39 3/31/06 2.2 -- 12.20 2,630 13.1 8.41 --

-- 11.45 1,002 14.3 128 --

-- 10.55 357 13.6 9.79 --

-- 9.41 393 13.2 -- --

10 9.27 394 13.5 -- --

4/6/06 -- -- 9.31 543 12.6 23 --

-- 9.16 553 12.8 14.26 --

8 8.96 573 12.9 13.28 --

PC-1B 3/31/06 1.3 -- 7.37 783 9.4 1,180 --

-- 7.32 788 9.9 1,124 --

3.5 7.28 788 9.9 1,098 --

4/6/06 1.25 3 7.88 825 9.0 72.1 --

PC-1C 3/31/06 6 -- 7.42 615 11.7 12.95 --

CRA 045136 (13) Byron Generating Station

TABLE 4.3 Page 5 of 5

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - MARCH/APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Well Volume Location Date Volume Purged pH Conductivity Temperature Turbidity Observations (gallons) (gallons) (Std. Units) (µS/cm) (1) (°C) (NTU) (2)

-- 7.37 615 11.9 6.89 --

7.5 7.47 615 11.9 4.76 --

4/6/06 -- 5 7.44 655 10.3 98.3 --

PC-2B 3/31/06 1.2 -- 7.49 683 12.0 798 --

-- 7.46 686 11.1 752 --

4 7.33 664 11.1 722 --

4/6/06 1.2 3.5 7.33 657 11.1 641 --

PC-5B 3/31/06 1.4 -- 7.69 776 10.6 1040 --

-- 7.35 782 10.5 182 --

-- 7.27 778 10.7 144 --

3.5 7.27 775 10.7 138 --

4/6/06 1.4 1.5 7.97 763 10.6 210 --

3 7.48 741 10.7 164 --

PC-6B 3/31/06 1.2 -- 7.15 975 14.1 540 --

-- 7.06 990 11.6 566 --

2.5 7.08 987 12.0 612 --

4/6/06 1.25 3.5 7.69 830 9.0 >999 --

TW-13 3/8/06 0.4 0.5 7.59 757 10.3 -- Clear 1 7.54 757 10.3 -- Clear 1.5 7.54 756 10.3 -- Clear 4/6/06 0.48 1 7.64 800 9.9 >999 --

4/12/06 0.5 -- 7.77 791 11.1 -- Murky

-- 7.70 770 10.4 -- Murky 1 7.72 775 10.3 -- Murky TW-14 4/6/06 1.5 1 7.83 842 10.6 >999 --

2 7.77 836 10.7 >999 --

3 7.69 819 10.7 >999 --

4/12/06 1.4 -- 7.59 793 11.2 -- Murky

-- 7.66 785 10.9 -- Murky 2.5 7.60 779 10.8 -- Murky TW-15 3/8/06 0.9 13 7.49 678 11.7 -- Slightly cloudy 14 7.48 681 11.7 -- Slightly cloudy 15 7.43 681 11.7 -- Slightly cloudy 4/6/06 1.12 1 7.71 782 9.8 >999 --

Dry at 2 No readings --

3 No readings --

4/12/06 1.1 -- 7.53 814 11.5 -- Murky

-- 7.52 775 10.3 -- Murky 2.5 7.51 776 10.3 -- Murky Notes:

(1) µS/cm - microSiemens per centimeter (2) NTU - nephelometric turbidity units CRA 045136 (13) Byron Generating Station

TABLE 4.4 Page 1 of 3 SAMPLE

SUMMARY

- BLOWDOWN LINE INVESTIGATION FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINIOS Sample Sample Location Sample Identification QC Sample Date Sample Analyses GW-9 GW-030806-KD-01 -- 3/8/2006 Tritium TW-13 GW-030806-KD-02 -- 3/8/2006 Tritium TW-13 GW-030806-KD-03 Duplicate 3/8/2006 Tritium TW-15 GW-030806-KD-04 -- 3/8/2006 Tritium CAR-1 GW-19232-032306-SP-CAR-1 -- 3/23/2006 Tritium AR-1 GW-19232-032306-SP-AR-1 -- 3/24/2006 Tritium AR-2 GW-19232-032306-SP-AR-2 -- 3/24/2006 Tritium AR-3 GW-19232-032306-SP-AR-3 -- 3/24/2006 Tritium AR-5 GW-19232-032306-SP-AR-5 -- 3/24/2006 Tritium AR-6 GW-19232-032306-SP-AR-6 -- 3/24/2006 Tritium CAR-2 GW-19232-032306-SP-CAR-2 -- 3/24/2006 Tritium AR-3 GW-19232-032706-NK-AR-3 -- 3/27/2006 Tritium AR-2 GW-19232-032708-EV-AR-2 -- 3/27/2006 Tritium AR-4 GW-19232-032806-NK-CAR-4 -- 3/28/2006 Tritium AR-5 GW-19232-032906-EV-AR-5 -- 3/29/2006 Tritium AR-6 GW-19232-032906-EV-AR-6 -- 3/29/2006 Tritium CAR-2 GW-19232-032906-EV-CAR-2 -- 3/29/2006 Tritium AR-4 GW-19232-032906-EV-CAR-4 -- 3/29/2006 Tritium AR-1 GW-19232-032906-NK-AR-1 -- 3/29/2006 Tritium AR-2 GW-19232-032906-NK-AR-2 -- 3/29/2006 Tritium AR-3 GW-19232-032906-NK-AR-3 -- 3/29/2006 Tritium CAR-1 GW-19232-032906-NK-CAR-1 -- 3/29/2006 Tritium AR-7 AR-7 -- 3/30/2006 Tritium CAR-3 CAR-3 -- 3/30/2006 Tritium DF-19 DF-19 -- 3/30/2006 Tritium DF-1D DF-1D -- 3/30/2006 Tritium DF-1S DF-1S -- 3/30/2006 Tritium DF-24 DF-24 -- 3/30/2006 Tritium DF-2S DF-2S -- 3/30/2006 Tritium DF-4DS DF-4DS -- 3/30/2006 Tritium DF-6 DF-6 -- 3/30/2006 Tritium DF-12 DF-12 -- 3/31/2006 Tritium DF-3S DF-3S -- 3/31/2006 Tritium MW-1 MW-1 -- 3/31/2006 Tritium MW-2 MW-2 -- 3/31/2006 Tritium MW-3 MW-3 -- 3/31/2006 Tritium MW-30 MW-30 -- 3/31/2006 Tritium MW-36 MW-36 -- 3/31/2006 Tritium MW-37 MW-37 -- 3/31/2006 Tritium MW-39 MW-39 -- 3/31/2006 Tritium PC-1B PC-1B -- 3/31/2006 Tritium PC-1C PC-1C -- 3/31/2006 Tritium CRA 45136(13) Bryon Generating Station

TABLE 4.4 Page 2 of 3 SAMPLE

SUMMARY

- BLOWDOWN LINE INVESTIGATION FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINIOS Sample Sample Location Sample Identification QC Sample Date Sample Analyses PC-2B PC-2B -- 3/31/2006 Tritium PC-5B PC-5B -- 3/31/2006 Tritium PC-5B PC-5B Duplicate 3/31/2006 Tritium PC-6B PC-6B -- 3/31/2006 Tritium AR-2 GW040306-NK-AR-2 -- 4/3/2006 Tritium AR-3 GW040306-NK-AR-3 -- 4/3/2006 Tritium AR-4 GW040406-NK-AR-4 -- 4/4/2006 Tritium (1)

AR-7 GW-040506-NK-AR-7 -- 4/5/2006 Tritium and Radionuclides AR-8 GW-040506-NK-AR-8 -- 4/5/2006 Tritium and Radionuclides AR-9 GW-040506-NK-AR-9 -- 4/5/2006 Tritium and Radionuclides CAR-3 GW-040506-NK-CAR-3 -- 4/5/2006 Tritium and Radionuclides AR-5 GW-040606-NK-AR-5 -- 4/6/2006 Tritium and Radionuclides AR-6 GW-040606-NK-AR-6 -- 4/6/2006 Tritium and Radionuclides DF-12 GW-040606-NK-DF-12 -- 4/6/2006 Tritium DF-24 GW-040606-NK-DF-24 -- 4/6/2006 Tritium DF-6 GW-040606-NK-DF-6 -- 4/6/2006 Tritium DF-6 GW-040606-NK-DF-6 Duplicate 4/6/2006 Tritium MW-1 GW-040606-NK-MW-12 -- 4/6/2006 Tritium MW-2 GW-040606-NK-MW-12 -- 4/6/2006 Tritium MW-36 GW-040606-NK-MW-36 -- 4/6/2006 Tritium MW-37 GW-040606-NK-MW-37 -- 4/6/2006 Tritium MW-39 GW-040606-NK-MW39 -- 4/6/2006 Tritium PC-1C GW-040606-NK-PC-1C -- 4/6/2006 Tritium MW-3 GW-19232-0406060-BW-MW-3 -- 4/6/2006 Tritium AR-1 GW-19232-040606-BW-AR-1 -- 4/6/2006 Tritium and Radionuclides AR-10 GW-19232-040606-BW-AR-10 -- 4/6/2006 Tritium and Radionuclides CAR-1 GW-19232-040606-BW-CAR-1 -- 4/6/2006 Tritium and Radionuclides CAR-2 GW-19232-040606-BW-CAR-2 -- 4/6/2006 Tritium and Radionuclides DF-19 GW-19232-040606-BW-DF-19 -- 4/6/2006 Tritium DF-1D GW-19232-040606-BW-DF-1D -- 4/6/2006 Tritium DF-1S GW-19232-040606-BW-DF-1S -- 4/6/2006 Tritium DF-2S GW-19232-040606-BW-DF-2S -- 4/6/2006 Tritium DF-4DS GW-19232-040606-BW-DF-4DS -- 4/6/2006 Tritium DF-4DS GW-19232-040606-BW-DF-4DS Duplicate 4/6/2006 Tritium PC-1B GW-19232-040606-BW-PC-1B -- 4/6/2006 Tritium PC-2B GW-19232-040606-BW-PC-2B -- 4/6/2006 Tritium PC-5B GW-19232-040606-BW-PC-5B -- 4/6/2006 Tritium PC-6B GW-19232-040606-BW-PC-6B -- 4/6/2006 Tritium TW-13 GW-19232-040606-BW-TW-13 -- 4/6/2006 Tritium and Radionuclides TW-14 GW-19232-040606-BW-TW-14 -- 4/6/2006 Tritium and Radionuclides TW-15 GW-19232-040606-BW-TW-15 -- 4/6/2006 Tritium and Radionuclides DF-3S GW-19232-040606-DW-DF-3S -- 4/6/2006 Tritium CRA 45136(13) Bryon Generating Station

TABLE 4.4 Page 3 of 3 SAMPLE

SUMMARY

- BLOWDOWN LINE INVESTIGATION FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINIOS Sample Sample Location Sample Identification QC Sample Date Sample Analyses MW-30 GW-19232-040606-GW-MW-30 -- 4/6/2006 Tritium AR-2 GW-19232-041006-EV-AR-2 -- 4/10/2006 Tritium and Radionuclides AR-3 GW-19232-041006-EV-AR-3 -- 4/10/2006 Tritium and Radionuclides AR-4 GW-19232-041006-EV-AR-4 -- 4/10/2006 Tritium and Radionuclides AR-5 GW-19232-041106-EV-AR-5 -- 4/11/2006 Tritium and Radionuclides AR-6 GW-19232-041106-EV-AR-6 -- 4/11/2006 Tritium and Radionuclides AR-7 GW-19232-041106-EV-AR-7 -- 4/11/2006 Tritium and Radionuclides AR-8 GW-19232-041106-EV-AR-8 -- 4/11/2006 Tritium and Radionuclides AR-9 GW-19232-041106-EV-AR-9 -- 4/11/2006 Tritium and Radionuclides CAR-3 GW-19232-041106-EV-CAR-3 -- 4/11/2006 Tritium and Radionuclides AR-1 GW-19232-041106-EV-AR-1 -- 4/12/2006 Tritium and Radionuclides AR-10 GW-19232-041106-EV-AR-10 -- 4/12/2006 Tritium and Radionuclides CAR-1 GW-19232-041106-EV-CAR-1 -- 4/12/2006 Tritium and Radionuclides CAR-2 GW-19232-041106-EV-CAR-2 -- 4/12/2006 Tritium and Radionuclides CAR-2 GW-19232-041106-EV-CAR-2 Duplicate 4/12/2006 Tritium and Radionuclides TW-14 GW-19232-041106-EV-TW-14 -- 4/12/2006 Tritium and Radionuclides TW-15 GW-19232-041106-EV-TW-15 -- 4/12/2006 Tritium and Radionuclides TW-13 GW-19232-041206-EV-TW-13 -- 4/12/2006 Tritium and Radionuclides AR-11 GW-041806-KD-AR-11 -- 4/18/2006 Tritium and Radionuclides Notes:

QC - Quality Control (1) Radionuclides: Sr-89/90, Mn-54, Fe-59, Co-58, Co-60, Zn-65, Zr-Nb-95, I-131, Cs-134, Cs-137, and Ba-La-140 CRA 45136(13) Bryon Generating Station

TABLE 4.5 Page 1 of 2

SUMMARY

OF GROUNDWATER ELEVATIONS - APRIL 24, 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS April 24, 2006 Sample Reference Depth to Groundwater Location Elevation Water Elevation (ft AMSL) (ft below Reference) (ft AMSL)

Exelon-Owned Wells AR-1 871.10 35.16 835.94 AR-2 867.38 68.88 798.50 AR-3 860.64 63.77 796.87 AR-4 832.74 90.00 742.74 AR-5 795.75 107.67 688.08 AR-6 784.55 109.55 675.00 AR-7 871.28 104.54 766.74 AR-8 872.11 33.56 838.55 AR-9 876.77 59.50 817.27 AR-10 859.15 21.49 837.66 AR-11 831.65 89.24 742.41 CAR-1 694.87 22.24 672.63 CAR-2 772.01 35.12 736.89 CAR-3 872.16 45.64 826.52 TW-13 700.47 17.11 683.36 TW-14 699.41 26.48 672.93 TW-15 695.73 22.84 672.89 GW-9 841.73 96.27 745.46 Well 7 891.24 115.77 775.47 Byron Salvage PRP Group-Owned Wells DF-1S 786.89 60.85 726.04 DF-1D 787.48 61.81 725.67 DF-2S 794.96 67.88 727.08 DF-3S 791.82 64.49 727.33 DF-4DS 832.98 67.16 765.82 DF-4DD 832.79 86.62 746.17 DF-5S 844.12 44.35 799.77 DF-6 827.89 88.69 739.20 DF-7S 712.38 Dry --

DF-7D 712.55 37.47 675.08 DF-8 757.47 39.87 717.60 DF-10 834.01 Dry --

DF-11 834.21 85.21 749.00 DF-12 834.48 88.42 746.06 DF-13 838.84 92.78 746.06 DF-15 847.79 106.81 740.98 DF-17 820.14 90.38 729.76 DF-18 780.28 54.56 725.72 CRA 045136 (13) Byron Generating Station

TABLE 4.5 Page 2 of 2

SUMMARY

OF GROUNDWATER ELEVATIONS - APRIL 24, 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS April 24, 2006 Sample Reference Depth to Groundwater Location Elevation Water Elevation (ft AMSL) (ft below Reference) (ft AMSL)

DF-19 788.53 62.93 725.60 DF-22S 811.85 85.51 726.34 DF-22D 811.56 85.22 726.34 DF-23 755.39 38.22 717.17 DF-24 813.68 89.89 723.79 DF-25 786.36 17.25 769.11 MW-1 861.77 62.14 799.63 MW-2 861.07 176.85 684.22 MW-3 858.6 71.09 787.51 MW-15 822.23 76.67 745.56 MW-16 823.47 77.91 745.56 MW-20R 821.85 140.66 681.19 MW-21 821.63 140.47 681.16 MW-30 758.68 38.42 720.26 MW-36 843.73 97.59 746.14 MW-37 843.33 161.18 682.15 MW-39 836.67 155.18 681.49 MW-41 816.87 71.38 745.49 MW-42 836.31 90.46 745.85 PC-1B 757.28 39.27 718.01 PC-1C 757.89 78.36 679.53 PC-2B 842.54 86.31 756.23 PC-3B 828.3 67.72 760.58 PC-4B 802.8 76.31 726.49 PC-5B 788.35 64.75 723.60 PC-6B 831.01 87.83 743.18 Notes:

ft AMSL - feet above Mean Sea Level CRA 045136 (13) Byron Generating Station

TABLE 4.7 Page 1 of 8

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - FLEETWIDE SAMPLING EVENT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Initial Depth Time Dissolved Depth to (3)

Location Date to Water Purged pH Temperature Conductivity Turbidity ORP Oxygen Water Observations (ft below Reference) (minutes) (Std. Units) (°C) (µS/cm) (1) (NTU) (2) (mV) (4)

(mg/L) (5) (ft below Reference)

AR-1 4/26/06 34.91 7 7.70 13.37 543 11.3 53.6 10.79 37.30 --

12 7.51 13.72 538 -- 57.3 9.68 -- --

Equipment malfunction 58 8.14 14.23 531 7.5 43.7 9.42 38.02 --

63 7.89 13.69 531 4.3 54.7 10.64 42.45 --

68 7.72 13.69 529 3.2 60.4 10.54 43.36 --

73 7.66 13.82 530 2.4 61.5 10.94 43.62 --

76 7.68 13.82 528 2.5 62.8 10.16 43.45 --

AR-2 4/26/06 68.72 10 7.18 13.28 814 50 112 8.20 72.45 Slightly cloudy, no odor 15 7.16 13.54 820 27 112 8.15 73.90 Slightly cloudy, no odor 20 7.11 13.84 814 22 114 7.97 74.03 Clear 25 7.13 13.22 814 18 114 7.89 74.10 Clear 30 7.15 13.20 820 15 110 7.86 74.14 Clear 35 7.14 13.18 824 16 109 7.82 74.17 Clear AR-3 4/26/06 63.90 10 7.02 13.09 683 50 91 6.58 64.10 Slightly cloudy, no odor 15 7.01 13.23 684 50 95 6.57 64.12 Slightly cloudy, no odor 20 6.98 13.20 682 33 100 6.32 64.13 Clear 25 7.01 13.17 683 19 101 6.29 64.15 Clear 30 6.98 13.22 682 12 105 6.40 64.17 Clear AR-4 4/27/06 89.63 8 7.99 15.90 1,138 232 30.1 7.45 93.27 --

13 9.22 15.86 1,133 265 31.4 6.97 93.59 --

18 9.69 15.44 1,125 294 30.3 6.48 93.91 --

23 9.66 15.79 1,125 282 29.3 5.90 94.31 --

28 9.60 15.86 1,123 270 28.3 5.40 94.62 --

33 9.27 16.10 1,124 252 31.3 5.11 94.88 --

36 9.33 16.19 1,124 226 30.2 4.92 95.00 --

39 9.25 16.57 1,124 208 29.7 4.72 95.09 --

42 9.20 16.67 1,125 188 30.6 4.62 95.15 --

AR-5 4/27/06 107.49 5 7.55 16.16 988 497 20.4 4.88 110.99 --

10 7.83 16.94 997 404 16.3 3.09 111.37 --

15 7.96 17.52 1,002 349 17.3 2.90 111.69 --

20 8.19 18.23 1,008 332 13.8 2.97 112.10 --

25 8.38 18.52 1,013 318 10.1 2.91 112.38 --

28 8.39 18.77 1,017 308 8.0 2.94 112.51 --

AR-6 4/27/06 109.51 5 7.55 15.83 606 119 15.1 5.58 111.75 --

10 7.76 15.48 599 167 11.7 3.23 112.47 --

15 7.60 17.21 608 167 17.5 2.83 112.43 --

20 7.49 17.93 612 197 18.1 2.70 112.74 --

25 7.54 18.56 617 154 16.5 2.52 113.10 --

CRA 045136 (13) Byron Generating Station

TABLE 4.7 Page 2 of 8

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - FLEETWIDE SAMPLING EVENT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Initial Depth Time Dissolved Depth to (3)

Location Date to Water Purged pH Temperature Conductivity Turbidity ORP Oxygen Water Observations (ft below Reference) (minutes) (Std. Units) (°C) (µS/cm) (1) (NTU) (2) (mV) (4)

(mg/L) (5) (ft below Reference) 30 7.52 19.82 615 99.1 17.9 2.17 113.50 --

35 7.52 20.94 616 90.2 18.4 2.04 113.59 --

38 7.51 21.23 619 75.9 18.3 2.02 113.66 --

AR-7 4/27/06 104.61 10 7.28 19.45 1,206 800 325 4.63 104.40 Brown color, no odor 15 7.42 19.08 1,199 577 333 3.70 104.60 Very cloudy 20 7.45 19.15 1,196 454 338 3.67 104.40 Very cloudy 25 7.31 21.10 1,221 978 335 3.46 104.40 Very cloudy 30 7.11 21.47 1,199 >1000 329 3.70 104.40 Brown color 35 7.39 18.58 1,190 304 337 3.79 104.40 Cloudy 40 7.60 18.38 1,191 79 340 3.76 104.40 Slightly cloudy 45 7.38 18.54 1,189 41.1 342 3.74 104.40 Slightly cloudy 48 7.29 18.65 1,190 25.5 343 3.75 104.40 Slightly cloudy 51 7.24 18.75 1,188 23 344 3.70 104.40 Clear 54 7.24 18.75 1,187 24 344 3.71 104.40 Clear AR-8 4/27/06 33.30 10 7.90 17.80 644 167 286 7.61 34.45 Cloudy 15 7.76 18.20 642 154 283 7.64 34.55 Cloudy 20 7.58 18.20 642 127 285 7.59 34.65 Cloudy 25 7.42 18.90 639 115 291 7.45 34.63 Cloudy 30 7.30 189.00 639 109 267 7.30 34.63 Cloudy 33 7.28 19.00 639 112 266 7.29 34.63 Cloudy AR-9 4/27/06 59.30 10 6.95 18.80 910 263 231 6.20 61.16 Cloudy 20 6.87 19.80 907 83 182 5.98 61.60 Slightly cloudy 25 6.83 20.80 906 32 175 5.59 61.90 Clear 28 6.80 20.50 907 29 180 5.60 61.90 Clear 31 6.80 20.50 908 29 175 5.59 61.90 Clear 33 6.80 20.50 908 29 177 5.59 61.90 Clear AR-10 4/26/06 21.46 10 7.05 13.00 3,220 90 119 1.11 21.55 Cloudy 15 7.04 12.56 3,225 70 118 1.11 21.55 Slightly cloudy 20 7.03 12.45 3,220 29 121 1.04 21.58 Clear 25 7.02 12.42 3,225 17 127 0.93 21.60 Clear 30 7.04 12.40 3,220 11 127 0.90 21.60 Clear AR-11 4/26/06 87.12 18 8.27 14.78 979 179 -0.8 5.89 -- --

23 8.82 14.40 983 200 5.5 2.36 97.57 --

28 8.69 15.17 983 138 16.6 1.70 98.32 --

33 8.66 14.83 979 111 18.2 1.36 99.72 --

38 7.49 15.55 980 77.7 29.6 1.14 100.20 --

43 8.48 15.40 977 69.3 19.6 1.03 100.71 --

48 8.53 15.86 978 59.5 16.7 0.99 100.70 --

53 8.32 15.53 972 79 22.7 0.95 100.70 --

58 8.38 14.75 975 115 21.2 0.91 101.09 --

CRA 045136 (13) Byron Generating Station

TABLE 4.7 Page 3 of 8

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - FLEETWIDE SAMPLING EVENT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Initial Depth Time Dissolved Depth to (3)

Location Date to Water Purged pH Temperature Conductivity Turbidity ORP Oxygen Water Observations (ft below Reference) (minutes) (Std. Units) (°C) (µS/cm) (1) (NTU) (2) (mV) (4)

(mg/L) (5) (ft below Reference) 61 8.37 14.78 967 101 20.0 0.86 101.68 --

64 8.45 14.76 964 68.5 19.0 0.78 102.15 --

67 8.43 14.71 966 52.1 16.9 0.69 102.43 --

70 8.43 14.92 969 46.1 15.9 0.69 102.59 --

73 8.43 14.79 967 46.5 15.3 0.69 102.75 --

CAR-1 4/27/06 22.51 7 7.93 12.80 552 514 42.9 7.52 22.63 --

12 6.96 13.15 547 285 52.3 6.78 22.61 --

17 8.22 13.13 546 102 44.3 6.69 22.61 --

22 8.32 13.06 548 41.1 42.3 6.70 22.63 --

27 6.22 13.08 547 16.6 55.9 6.67 22.64 --

32 6.56 13.23 546 8.4 51.3 6.62 22.64 --

35 6.52 13.20 548 8.4 49.6 6.74 22.63 --

38 6.59 13.17 546 5.5 48.7 6.71 22.63 --

CAR-2 4/27/06 35.23 0 8.06 14.02 822 32.5 29.3 10.74 -- --

3 8.20 12.60 817 23.8 19.9 10.40 -- --

CAR-3 4/27/06 45.40 10 7.15 21.40 974 12 244 7.00 46.10 Clear 13 7.08 21.50 986 10 254 7.00 46.10 Clear 16 7.08 21.50 990 7.5 255 6.99 46.10 Clear 19 7.08 21.50 991 4.8 256 6.99 46.10 Clear DF-1D 4/25/06 61.81 7 8.43 12.89 801 4.16 25.7 3.58 61.95 --

12 8.26 13.23 808 2.21 27.0 2.88 61.95 --

17 8.30 13.42 808 1.79 33.6 2.70 61.95 --

22 8.41 13.36 809 1.78 18.2 2.63 61.95 --

25 8.49 13.26 807 1.74 13.9 2.60 61.95 --

28 8.52 13.32 807 1.71 10.5 2.59 61.95 --

31 8.49 13.24 809 1.87 11.7 2.59 61.95 --

36 8.62 13.19 807 1.5 10.4 2.55 61.95 --

DF-1S 4/25/06 60.83 10 6.98 14.09 804 100 -110 0.40 61.03 Slightly cloudy, no odor 15 7.00 13.34 794 65 -115 0.40 60.96 Slightly cloudy, no odor 20 7.04 14.10 798 65 -125 0.33 60.97 Slightly cloudy, no odor 25 7.02 14.12 792 50 -130 0.29 60.99 Slightly cloudy, no odor 30 6.99 14.04 788 40 -123 0.28 61.02 Slightly cloudy, no odor DF-2S 4/25/06 67.81 10 7.00 12.25 687 9.4 65 3.17 70.74 Clear 15 7.05 11.54 691 13 39 2.50 71.42 Clear 20 7.00 11.55 694 9.4 40 2.29 72.40 Clear 25 6.98 11.55 691 7.1 42 2.28 72.66 Clear 30 6.99 11.54 690 7 40 2.25 72.69 Clear CRA 045136 (13) Byron Generating Station

TABLE 4.7 Page 4 of 8

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - FLEETWIDE SAMPLING EVENT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Initial Depth Time Dissolved Depth to (3)

Location Date to Water Purged pH Temperature Conductivity Turbidity ORP Oxygen Water Observations (ft below Reference) (minutes) (Std. Units) (°C) (µS/cm) (1) (NTU) (2) (mV) (4)

(mg/L) (5) (ft below Reference)

DF-3S 4/25/06 64.47 10 6.95 10.81 728 110 140 4.44 64.52 Cloudy, yellow, no odor Slightly cloudy, yellow, no 15 6.95 10.87 737 70 141 3.89 64.52 odor 20 6.96 10.98 745 37 139 3.38 64.52 Slightly cloudy DF-4DS 4/25/06 57.20 10 6.96 9.68 669 55 139 7.21 59.15 Slightly cloudy, no odor 15 6.96 10.45 670 37 130 7.48 60.35 Slightly cloudy, no odor 20 6.96 10.70 668 270 89.0 6.83 61.35 Cloudy DF-6 4/25/06 88.18 13 8.99 11.99 881 12.3 12.2 1.60 96.10 --

18 8.69 12.46 671 12.3 15.1 1.13 98.00 --

23 8.54 13.36 665 12.9 9.4 1.13 98.61 --

28 8.81 14.35 660 12.9 8.6 1.08 100.30 --

31 8.60 14.80 661 12.9 14.3 1.07 101.02 --

34 8.60 14.75 661 12.7 18.7 1.03 101.95 --

DF-12 4/25/06 88.42 10 6.52 12.51 775 2.4 11.4 7.58 88.39 --

15 6.77 12.51 772 1.9 20.7 7.08 88.42 --

20 6.98 12.51 772 1.8 -2.1 6.97 88.41 --

30 8.67 11.89 768 1.6 -26.6 7.00 88.42 --

35 9.24 11.91 768 1.5 -34.3 6.97 88.40 --

40 9.55 11.90 768 1.1 -41.5 6.99 88.40 --

45 9.80 11.90 767 1.4 -45.8 6.97 88.40 --

48 9.81 11.90 767 1.3 -44.6 6.97 88.40 --

51 10.16 11.90 767 0.8 -53.2 6.94 88.40 --

54 10.17 11.90 767 1 -51.2 6.90 88.40 --

57 10.23 11.91 767 1.2 -53.7 6.84 88.40 --

DF-13 4/26/06 93.13 5 10.03 14.87 825 25.6 -5.5 3.43 93.30 --

10 9.77 15.12 807 20 5.7 2.16 93.30 --

15 9.50 15.37 794 12.5 4.8 1.97 93.30 --

20 9.42 15.41 788 9.5 5.5 1.97 93.30 --

25 9.29 15.33 785 7.5 7.1 1.97 93.30 --

28 9.31 15.28 784 7 5.5 1.97 93.30 --

DF-19 4/25/06 62.93 10 6.95 10.48 760 >1000 73 2.48 63.04 Orange, no odor 15 6.97 11.12 781 >1000 32 1.28 63.08 Very cloudy, orange 20 6.98 11.07 785 589 1 1.01 63.07 Cloudy, orange tint 25 6.95 11.09 791 334 -7 0.93 63.08 Cloudy 30 6.98 11.19 786 191 -18 0.96 63.08 Cloudy 35 6.97 11.41 785 128 -19 0.96 63.08 Cloudy 40 6.98 11.34 785 120 -13 0.95 63.08 Cloudy 45 6.95 11.35 786 85 -11 0.97 63.08 Cloudy DF-24 4/25/06 89.91 7 9.33 12.49 855 3.75 21.5 7.28 89.91 --

CRA 045136 (13) Byron Generating Station

TABLE 4.7 Page 5 of 8

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - FLEETWIDE SAMPLING EVENT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Initial Depth Time Dissolved Depth to (3)

Location Date to Water Purged pH Temperature Conductivity Turbidity ORP Oxygen Water Observations (ft below Reference) (minutes) (Std. Units) (°C) (µS/cm) (1) (NTU) (2) (mV) (4)

(mg/L) (5) (ft below Reference) 12 9.33 13.01 850 28.2 19.8 7.21 89.91 --

17 8.88 13.10 843 22.4 28.6 7.42 89.91 --

22 8.74 13.16 842 19.4 31.3 7.51 89.91 --

25 8.75 13.08 840 17.3 30.7 7.56 89.91 --

GW-9 4/28/06 96.30 10 7.21 14.40 963 11 389 5.68 97.00 Clear 15 6.65 15.20 962 7 395 5.70 97.50 Clear 20 6.65 15.20 962 6.6 396 5.73 97.50 Clear 23 6.63 15.20 962 6.8 396 5.72 97.50 Clear 26 6.63 15.20 961 7 396 5.72 97.50 Clear MW-1 4/26/06 62.30 10 7.03 10.09 543 >1000 -17 5.12 63.75 Tan color, no odor 15 7.03 10.75 549 >1000 -11 4.97 64.25 Tan color, no odor 20 7.03 11.11 549 >1000 -2 4.63 64.55 Tan color, no odor 25 7.01 11.38 549 >1000 10 4.56 64.81 Tan color, no odor 30 7.00 11.41 553 >1000 3.7 4.75 64.95 Brownish color 35 7.06 11.72 539 >1000 26 5.31 65.70 Very cloudy 40 6.99 11.46 536 >1000 38 5.31 65.95 Very cloudy 45 7.00 11.40 535 >1000 40 5.36 65.99 Very cloudy 50 7.01 11.45 537 >1000 41 5.35 65.99 Very cloudy 55 7.04 11.36 533 950 44 5.41 66.00 Very cloudy 60 7.04 11.33 531 950 46 5.45 66.00 Very cloudy MW-2 4/27/06 177.10 5 8.06 13.06 489 4.5 -68.9 1.79 178.34 --

10 8.01 14.16 509 8.4 -72.5 0.98 178.51 --

15 7.72 14.26 564 4.2 -37.3 0.84 178.60 --

20 7.62 14.02 568 2.3 -21.2 0.72 178.66 --

25 7.56 13.88 569 1.9 -11.8 0.68 178.66 --

30 7.53 13.96 568 2.4 -7.3 0.63 178.70 --

33 7.52 13.92 569 2 -4.7 0.61 178.70 --

MW-3 4/26/06 71.45 10 6.97 11.13 639 100 37 8.15 72.39 Slightly cloudy 15 7.02 11.70 639 90 37 8.08 73.53 Slightly cloudy 20 7.02 11.94 638 65 41 8.01 73.86 Slightly cloudy 25 7.00 11.99 637 65 47 8.05 74.37 Slightly cloudy 30 6.99 12.05 638 60 55 8.02 74.87 Slightly cloudy 35 6.99 12.09 637 55 60 7.94 74.90 Slightly cloudy 40 6.99 12.10 637 55 63 8.06 74.92 Slightly cloudy MW-30 4/28/06 38.51 15 6.51 11.26 579 >1000 148.9 10.55 -- --

MW-36 4/25/06 97.16 5 9.26 12.19 974 79.4 23.8 3.66 99.70 --

10 8.55 13.46 973 32.2 25.9 1.59 99.80 --

15 9.59 13.32 852 20 11.3 1.04 99.80 --

CRA 045136 (13) Byron Generating Station

TABLE 4.7 Page 6 of 8

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - FLEETWIDE SAMPLING EVENT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Initial Depth Time Dissolved Depth to (3)

Location Date to Water Purged pH Temperature Conductivity Turbidity ORP Oxygen Water Observations (ft below Reference) (minutes) (Std. Units) (°C) (µS/cm) (1) (NTU) (2) (mV) (4)

(mg/L) (5) (ft below Reference) 20 9.99 13.31 828 20 2.2 0.91 99.80 --

25 9.98 13.34 818 12.3 1.6 0.82 99.80 --

30 9.88 13.45 814 9.86 10.9 0.73 99.93 --

MW-37 4/26/06 161.37 5 8.99 14.14 602 17.2 35.6 1.80 161.95 --

10 8.57 15.06 603 8.8 34.3 0.90 161.97 --

15 8.82 14.83 601 4.9 32.2 0.65 162.03 --

20 8.82 14.68 599 3.5 32.2 0.57 162.02 --

23 8.69 14.62 598 3.1 33.3 0.54 162.02 --

MW-39 4/26/06 154.82 5 10.98 13.76 637 682 -10.8 6.35 157.18 --

10 10.25 16.16 551 325 19.5 1.99 157.50 --

15 9.88 15.75 589 54.5 26.4 1.35 -- --

20 9.77 15.58 598 28.9 26 1.05 -- --

25 9.84 15.57 598 18.8 24.9 0.89 157.64 --

30 9.83 15.59 599 16.3 23.5 0.76 157.64 --

33 9.68 15.65 600 15.4 24.9 0.69 157.54 --

36 9.74 15.67 598 16.8 23.8 0.66 157.64 --

PC-1B 4/26/06 39.28 35 7.18 12.53 790 6.7 56.9 6.70 39.23 --

40 7.30 12.59 792 6.2 59.0 6.29 39.23 --

45 7.33 12.60 794 4.7 60.7 6.26 39.34 --

48 7.64 12.59 794 3.85 54.0 6.27 39.34 --

51 7.64 12.56 795 3.54 52.7 6.27 39.34 --

54 7.69 12.59 794 3.27 51.4 6.27 39.34 --

PC-1C 4/26/06 78.63 9 9.10 12.61 619 393 17.0 8.07 79.44 --

14 8.58 12.64 617 275 21.0 3.83 79.44 --

19 8.44 12.65 615 187 24.0 3.54 79.44 --

24 8.34 12.67 615 103 26.1 3.50 79.44 --

29 8.28 12.68 614 58.3 27.8 3.49 79.46 --

34 8.22 12.71 612 42.3 29.3 3.53 79.46 --

37 8.18 12.75 612 37.7 29.9 3.57 79.46 --

40 8.19 12.80 612 34.7 30.9 3.56 79.46 --

43 8.16 12.85 610 30.7 31.6 3.61 79.46 --

PC-2B 4/25/06 86.67 10 9.80 13.40 696 21.1 28.4 9.60 87.79 --

15 8.68 13.93 695 23 0.8 7.26 87.90 --

20 7.22 14.88 686 18.6 53.3 7.18 88.17 --

25 8.11 14.50 691 22.5 27.3 6.99 88.85 --

30 8.17 13.77 692 13.2 26.3 6.97 89.38 --

35 8.35 12.72 694 22.4 19.7 6.89 89.78 --

40 8.52 11.76 693 22.6 13.6 6.93 89.95 --

45 8.61 11.06 692 23.9 17.5 6.75 90.28 --

CRA 045136 (13) Byron Generating Station

TABLE 4.7 Page 7 of 8

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - FLEETWIDE SAMPLING EVENT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Initial Depth Time Dissolved Depth to (3)

Location Date to Water Purged pH Temperature Conductivity Turbidity ORP Oxygen Water Observations (ft below Reference) (minutes) (Std. Units) (°C) (µS/cm) (1) (NTU) (2) (mV) (4)

(mg/L) (5) (ft below Reference) 50 8.26 18.73 705 -- 14.7 6.07 -- --

PC-5B 4/25/06 164.94 5 9.92 12.84 813 79.9 -11.6 6.62 64.94 --

10 9.23 13.02 815 25 -11.0 4.90 64.94 --

15 9.17 13.05 815 10.1 -5.7 4.70 64.94 --

20 9.15 13.02 815 5.48 -4.4 4.69 64.94 --

25 9.13 13.02 815 4.34 -3.7 4.69 64.94 --

28 9.13 13.01 816 3.75 -3.6 4.69 64.94 --

PC-6B 4/26/06 87.78 10 8.27 14.38 929 123 -2.5 6.77 90.11 --

15 8.24 14.59 927 145 -2.2 6.37 90.20 --

20 8.18 15.42 932 141 -1.7 5.94 90.21 --

25 8.10 15.81 934 114 -0.6 5.57 90.15 --

30 8.03 16.00 936 93.2 1.3 5.52 89.97 --

35 8.02 15.96 936 77.2 1.5 5.40 89.93 --

40 7.94 15.82 935 67.1 3 5.15 89.73 --

45 7.93 15.75 936 58.1 2.1 5.22 89.73 --

50 7.92 16.01 937 48.1 0.7 5.18 89.69 --

TW-13 4/27/06 17.16 7 6.69 13.16 784 >1000 26.7 12.38 17.37 --

12 6.87 11.90 769 268 36.2 10.52 17.37 --

17 6.87 12.03 768 71.8 43.7 10.42 17.37 --

22 6.89 11.97 769 26.2 43.3 10.44 17.37 --

27 6.93 11.91 771 12.1 41.6 10.58 17.37 --

32 6.94 11.94 770 8 39.8 10.48 17.37 --

35 6.89 11.96 770 6.6 39.6 10.47 17.37 --

TW-14 4/27/06 26.72 7 7.31 13.28 742 712 43.0 8.88 26.73 --

12 7.33 14.34 738 570 39.2 7.57 26.74 --

17 7.34 14.66 742 448 38.1 7.50 26.75 --

22 7.26 14.64 742 362 38.3 7.58 26.74 --

27 6.89 14.78 740 299 39.3 7.47 26.75 --

32 6.93 14.90 738 257 38.4 7.41 26.72 --

35 7.21 14.98 739 236 35.0 7.19 26.74 --

38 7.06 15.11 739 203 36.6 7.23 26.73 --

41 7.56 15.24 739 178 32.7 7.19 26.73 --

44 7.49 15.45 739 164 33.8 7.26 26.73 --

47 7.46 15.48 739 158 33.4 7.17 26.73 --

TW-15 4/27/06 23.08 13 7.08 12.83 738 261 34.3 8.18 23.08 --

18 7.34 12.82 735 107 40.4 7.95 23.08 --

23 6.91 12.81 734 49 46.6 7.99 23.08 --

28 6.85 12.88 732 25.4 47.4 7.99 23.08 --

31 6.89 12.69 732 18.5 46.3 8.06 23.08 --

CRA 045136 (13) Byron Generating Station

TABLE 4.7 Page 8 of 8

SUMMARY

OF MONITORING WELL PURGING PARAMETERS - FLEETWIDE SAMPLING EVENT FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Initial Depth Time Dissolved Depth to (3)

Location Date to Water Purged pH Temperature Conductivity Turbidity ORP Oxygen Water Observations (ft below Reference) (minutes) (Std. Units) (°C) (µS/cm) (1) (NTU) (2) (mV) (4)

(mg/L) (5) (ft below Reference) 34 6.92 12.62 732 15.1 45.0 8.16 23.08 --

37 6.90 12.70 731 9.7 43.4 8.19 23.08 --

Well 7 4/27/06 115.60 10 8.00 14.60 791 10 369 7.50 115.60 Clear 15 7.36 15.90 790 12 375 7.30 115.60 Clear 18 7.27 16.20 790 11 375 7.26 115.60 Clear 21 7.25 16.30 790 10 376 7.24 115.60 Clear 24 7.25 16.30 790 10 376 7.24 115.60 Clear Notes:

(1) µS/cm - microSiemens per centimeter (2) NTU - nephelometric turbidity units (3) ORP - oxidation reduction potential (4) mV - millivolts (5) mg/L - milligrams per liter CRA 045136 (13) Byron Generating Station

TABLE 5.1 Page 1 of 1 CALCULATED VERTICAL HYDRAULIC GRADIENTS FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Well Elevation of Water Level Vertical Cluster Screen Middle April 24, 2006 Gradient (ft AMSL) (1) (ft AMSL) (ft/ft downward)

Water Table to Lower Galena-Platteville AR-4 720.7 742.74 0.009 AR-11 684.9 742.41 TW-14 668.4 672.93 0.011 CAR-1 642.3 672.63 DF-1S 734.0 726.04 0.013 DF-1D 704.8 725.67 PC-3B 754.1 760.58 0.443 DF-6 705.8 739.20 DF-11 757.6 749.00 0.053 DF-12 701.9 746.06 DF-22S 727.7 726.34 0.0 DF-22D 705.2 726.34 MW-30 722.7 720.26 0.095 DF-23 690.1 717.17 MW-15 740.7 745.56 0.0 MW-16 706.8 745.56 PC-1B 714.5 718.01 0.021 DF-8 694.6 717.60 Across the Glenwood Formation MW-1 818.0 799.63 0.622 MW-2 632.6 684.22 MW-16 706.8 745.56 0.892 MW-20R 634.6 681.19 MW-36 690.6 746.14 1.379 MW-37 644.2 682.15 MW-42 688.2 745.85 1.893 MW-39 654.2 681.49 DF-8 694.6 717.60 0.850 PC-1C 649.8 679.53 Within the St. Peter Sandstone MW-20R 634.6 681.19 0.001 MW-21 591.4 681.16 Notes:

(1) ft AMSL - feet above Mean Sea Level CRA 045136 (13) Byron Generating Station

TABLE 5.2 Page 1 of 1

SUMMARY

OF TRITIUM CONCENTRATIONS IN WATER - STATION SAMPLING LOCATIONS FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Result Sample Location Sample Identification Sample Date Laboratory Analysis Tritium (pCi/L) Error ABANDONED VAULT ABANDONED VAULT 2/3/2006 EI ND (200) -

CROP CROP 3/23/2006 EI ND (200) -

CWBD STEEL POT CWBD STEEL POT 2/27/2006 EI ND (200) -

CWBD STEEL POT 1CW 4/24/2006 EI 263 +/-89 OREPRO10 OREPRO10 2/27/2006 EI ND (200) -

Potable Water POTABLE WATER 3/23/2006 EI ND (200) -

VAULT #1 1 Blowdown 3/16/2006 EI ND (1960) * -

VAULT #2 VAULT #2 2/3/2006 EI 40727 +/-552 VAULT #2 VAULT #2 2/16/2006 EI 33900 NR VAULT #2 VAULT #2 3/2/2006 EI 1680 NR VAULT #2 2 Blowdown 3/16/2006 EI ND (1960) * -

VAULT #3 VAULT #3 2/3/2006 EI 37895 +/-523 VAULT #3 VAULT #3 2/16/2006 EI 34400 NR VAULT #3 3 Blowdown 3/16/2006 EI 7730 NR VAULT #4 VAULT #4 2/3/2006 EI 80123 +/-756 VAULT #4 VAULT #4 2/16/2006 EI 72300 NR VAULT #4 VAULT #4 3/2/2006 EI 18100 NR VAULT #4 4 Blowdown 3/16/2006 EI 9100 NR VAULT #4 Vault 4 4/24/2006 EI 375 +/-93 VAULT #5 VAULT #5 2/3/2006 EI 1843 +/-138 VAULT #5 VAULT #5 2/16/2006 EI 5430 NR VAULT #5 5 Blowdown 3/16/2006 EI 3130 NR VAULT #5 Vault 5 4/24/2006 EI 423 +/-95 VAULT #6 VAULT #6 2/3/2006 EI 29162 +/-460 VAULT #6 VAULT #6 2/16/2006 EI 29600 NR VAULT #6 6 Blowdown 3/16/2006 EI 7580 NR VAULT #6 Vault 6 4/24/2006 EI 645 +/-103 Notes:

EI - Environmental, Inc.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

- Non-detect at the value in parentheses.

NR - +/- value not reported.

- - Non-detect value, +/- value not reported.

CRA 45136 (13) Byron Generating Station

TABLE 5.3 Page 1 of 3

SUMMARY

OF TRITIUM CONCENTRATIONS IN GROUNDWATER - FEBRUARY - APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Result Sample Location Sample Identification Sample Date QC Sample Laboratory Analyses Tritium (pCi/L) Error AR-1 GW-19232-032306-SP-AR-1 3/24/2006 EI ND (200) -

AR-1 GW-19232-032906-NK-AR-1 3/29/2006 EI ND (200) -

AR-1 GW-19232-040606-BW-AR-1 4/6/2006 EI ND (200) -

AR-1 GW-19232-041106-EV-AR-1 4/12/2006 EI ND (200) -

AR-1 WG-BYN-042606-SS-25 4/26/2006 TBE ND (200) -

AR-2 GW-19232-032306-SP-AR-2 3/24/2006 EI 205 +/-84 AR-2 GW-19232-032306-SP-AR-2 3/24/2006 EI Recount ND (200) -

AR-2 GW-19232-032306-SP-AR-2 3/24/2006 EI Repeat Recount ND (200) -

AR-2 GW-19232-032708-EV-AR-2 3/27/2006 EI 315 +/-96 AR-2 GW-19232-032906-NK-AR-2 3/29/2006 EI 361 +/-95 AR-2 GW-19232-032906-NK-AR-2 3/29/2006 EI Original Recount 208 +/-96 AR-2 GW-19232-032906-NK-AR-2 3/29/2006 EI Original Recount #2 223 +/-97 AR-2 GW-19232-032906-NK-AR-2 3/29/2006 EI 1st Repeat ND (200) -

AR-2 GW-19232-032906-NK-AR-2 3/29/2006 EI 1st Repeat Recount 200 +/-96 AR-2 GW-19232-032906-NK-AR-2 3/29/2006 EI 2nd Repeat ND (200) -

AR-2 GW-19232-032906-NK-AR-2 3/29/2006 EI 2nd Repeat Recount ND (200) -

AR-2 GW040306-NK-AR-2 4/3/2006 EI 442 +/-100 AR-2 GW040306-NK-AR-2 4/3/2006 EI Recount 475 +/-93 AR-2 GW-19232-041006-EV-AR-2 4/10/2006 EI 566 NR AR-2 WG-BYN-042606-JK-22 4/26/2006 TBE 432 +/-140 AR-2 WG-BYN-042606-JK-22 4/26/2006 TBE Re-run 527 +/-142 AR-3 GW-19232-032306-SP-AR-3 3/24/2006 EI 214 +/-84 AR-3 GW-19232-032306-SP-AR-3 3/24/2006 EI Recount ND (200) -

AR-3 GW-19232-032306-SP-AR-3 3/24/2006 EI Repeat Recount 271 +/-95 AR-3 GW-19232-032706-NK-AR-3 3/27/2006 EI 459 +/-124 AR-3 GW-19232-032706-NK-AR-3 3/27/2006 EI Recount 346 +/-109 AR-3 GW-19232-032906-NK-AR-3 3/29/2006 EI 372 +/-122 AR-3 GW040306-NK-AR-3 4/3/2006 EI 489 +/-102 AR-3 GW-19232-041006-EV-AR-3 4/10/2006 EI 351 NR AR-3 WG-BYN-042606-JK-20 4/26/2006 TBE 234 +/-128 AR-4 GW-19232-032806-NK-CAR-4 3/28/2006 EI 3572 +/-198 AR-4 GW-19232-032806-NK-CAR-4 3/28/2006 EI Recount 3631 +/-192 AR-4 GW-19232-032906-EV-CAR-4 3/29/2006 EI 3817 +/-202 AR-4 GW040406-NK-AR-4 4/4/2006 EI 3741 +/-183 AR-4 GW-19232-041006-EV-AR-4 4/10/2006 EI 3469 NR AR-4 WG-BYN-042706-SS-44 4/27/2006 TBE 3260 +/-367 AR-4 WG-BYN-042706-SS-44 4/27/2006 TBE Re-run 4080 +/-463 AR-5 GW-19232-032306-SP-AR-5 3/24/2006 EI ND (200) -

AR-5 GW-19232-032906-EV-AR-5 3/29/2006 EI ND (200) -

AR-5 GW-040606-NK-AR-5 4/6/2006 EI ND (200) -

AR-5 GW-19232-041106-EV-AR-5 4/11/2006 EI ND (200) -

AR-5 WG-BYN-042706-SS-42 4/27/2006 TBE ND (200) -

AR-6 GW-19232-032306-SP-AR-6 3/24/2006 EI ND (200) -

AR-6 GW-19232-032906-EV-AR-6 3/29/2006 EI ND (200) -

AR-6 GW-040606-NK-AR-6 4/6/2006 EI ND (200) -

AR-6 GW-19232-041106-EV-AR-6 4/11/2006 EI ND (200) -

AR-6 WG-BYN-042706-SS-41 4/27/2006 TBE ND (200) -

AR-7 AR-7 3/30/2006 EI ND (200) -

AR-7 GW-040506-NK-AR-7 4/5/2006 EI ND (200) -

AR-7 GW-19232-041106-EV-AR-7 4/11/2006 EI ND (200) -

AR-7 WG-BYN-042706-KD-32 4/27/2006 TBE ND (200) -

AR-8 GW-040506-NK-AR-8 4/5/2006 EI ND (200) -

AR-8 GW-19232-041106-EV-AR-8 4/11/2006 EI ND (200) -

AR-8 WG-BYN-042706-KD-30 4/27/2006 TBE ND (200) -

AR-9 GW-040506-NK-AR-9 4/5/2006 EI ND (200) -

AR-9 GW-19232-041106-EV-AR-9 4/11/2006 EI ND (200) -

AR-9 WG-BYN-042706-KD-26 4/27/2006 TBE ND (200) -

AR-10 GW-19232-040606-BW-AR-10 4/6/2006 EI ND (200) -

AR-10 GW-19232-041106-EV-AR-10 4/12/2006 EI ND (200) -

AR-10 WG-BYN-042606-JK-24 4/26/2006 TBE ND (200) -

AR-11 GW-041806-KD-AR-11 4/18/2006 EI 2260 +/-162 AR-11 GW-041806-KD-AR-11 4/18/2006 EI Repeat 1965 NR AR-11 WG-BYN-042606-SS-27 4/26/2006 TBE 2340 +/-282 AR-11 WG-BYN-042606-SS-27 4/26/2006 TBE Re-run 2340 +/-282 CRA 045136 (13) Byron Generating Station

TABLE 5.3 Page 2 of 3

SUMMARY

OF TRITIUM CONCENTRATIONS IN GROUNDWATER - FEBRUARY - APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Result Sample Location Sample Identification Sample Date QC Sample Laboratory Analyses Tritium (pCi/L) Error CAR-1 GW-19232-032306-SP-CAR-1 3/23/2006 EI ND (200) -

CAR-1 GW-19232-032906-NK-CAR-1 3/29/2006 EI ND (200) -

CAR-1 GW-19232-040606-BW-CAR-1 4/6/2006 EI ND (200) -

CAR-1 GW-19232-041106-EV-CAR-1 4/12/2006 EI ND (200) -

CAR-1 WG-BYN-042706-SS-36 4/27/2006 TBE ND (200) -

CAR-2 GW-19232-032306-SP-CAR-2 3/24/2006 EI ND (200) -

CAR-2 GW-19232-032906-EV-CAR-2 3/29/2006 EI ND (200) -

CAR-2 GW-19232-040606-BW-CAR-2 4/6/2006 EI ND (200) -

CAR-2 GW-19232-041106-EV-CAR-2 4/12/2006 EI ND (200) -

CAR-2 GW-19232-041106-EV-CAR-2 4/12/2006 Duplicate (CAR-2) EI ND (200) -

CAR-2 WG-BYN-042706-SS-47 4/27/2006 TBE ND (200) -

CAR-3 CAR-3 3/30/2006 EI ND (200) -

CAR-3 GW-040506-NK-CAR-3 4/5/2006 EI ND (200) -

CAR-3 GW-19232-041106-EV-CAR-3 4/11/2006 EI ND (200) -

CAR-3 WG-BYN-042706-KD-28 4/27/2006 TBE ND (200) -

DF-1D DF-1D 3/30/2006 EI ND (200) -

DF-1D GW-19232-040606-BW-DF-1D 4/6/2006 EI ND (200) -

DF-1D WG-BYN-042506-SS-03 4/25/2006 TBE ND (200) -

DF-1S DF-1S 3/30/2006 EI ND (200) -

DF-1S GW-19232-040606-BW-DF-1S 4/6/2006 EI ND (200) -

DF-1S WG-BYN-042506-JK-04 4/25/2006 TBE ND (200) -

DF-2S DF-2S 3/30/2006 EI ND (200) -

DF-2S GW-19232-040606-BW-DF-2S 4/6/2006 EI ND (200) -

DF-2S WG-BYN-042506-JK-06 4/25/2006 TBE ND (200) -

DF-3S DF-3S 3/31/2006 EI ND (200) -

DF-3S GW-19232-040606-DW-DF-3S 4/6/2006 EI ND (200) -

DF-3S WG-BYN-042506-JK-08 4/25/2006 TBE ND (200) -

DF-3S WG-BYN-042506-JK-10 4/25/2006 Duplicate (JK-08) TBE ND (200) -

DF-4DS DF-4DS 3/30/2006 EI ND (200) -

DF-4DS GW-19232-040606-BW-DF-4DS 4/6/2006 EI ND (200) -

DF-4DS GW-19232-040606-BW-DF-4DS 4/6/2006 Duplicate (DF-4DS) EI ND (200) -

DF-4DS WG-BYN-042506-JK-02 4/25/2006 TBE ND (200) -

DF-6 DF-6 3/30/2006 EI ND (200) -

DF-6 GW-040606-NK-DF-6 4/6/2006 EI ND (200) -

DF-6 GW-040606-NK-DF-6 4/6/2006 Duplicate (DF-6) EI ND (200) -

DF-6 WG-BYN-042506-SS-05 4/25/2006 TBE ND (200) -

DF-12 DF-12 3/31/2006 EI ND (200) -

DF-12 GW-040606-NK-DF-12 4/6/2006 EI ND (200) -

DF-12 WG-BYN-042506-SS-01 4/25/2006 TBE ND (200) -

DF-13 WG-BYN-042606-SS-31 4/26/2006 TBE ND (200) -

DF-19 DF-19 3/30/2006 EI ND (200) -

DF-19 GW-19232-040606-BW-DF-19 4/6/2006 EI ND (200) -

DF-19 WG-BYN-042506-JK-12 4/25/2006 TBE ND (200) -

DF-24 DF-24 3/30/2006 EI ND (200) -

DF-24 GW-040606-NK-DF-24 4/6/2006 EI ND (200) -

DF-24 WG-BYN-042506-SS-13 4/25/2006 TBE ND (200) -

GW-9 GW-030806-KD-01 3/8/2006 EI ND (200) -

GW-9 WG-BYN-042806-KD-48 4/28/2006 TBE ND (200) -

MW-1 MW-1 3/31/2006 EI ND (200) -

MW-1 GW-040606-NK-MW-12 4/6/2006 EI ND (200) -

MW-1 WG-BYN-042606-JK-14 4/26/2006 TBE ND (200) -

MW-2 MW-2 3/31/2006 EI ND (200) -

MW-2 GW-040606-NK-MW-12 4/6/2006 EI ND (200) -

MW-2 WG-BYN-042706-SS-34 4/27/2006 TBE ND (200) -

MW-3 MW-3 3/31/2006 EI ND (200) -

MW-3 GW-19232-0406060-BW-MW-3 4/6/2006 EI ND (200) -

MW-3 WG-BYN-042606-JK-18 4/26/2006 TBE ND (200) -

MW-30 MW-30 3/31/2006 EI ND (200) -

MW-30 GW-19232-040606-GW-MW-30 4/6/2006 EI ND (200) -

MW-30 WG-BYN-042806-SS-49 4/28/2006 TBE ND (200) -

MW-36 MW-36 3/31/2006 EI ND (200) -

MW-36 GW-040606-NK-MW-36 4/6/2006 EI ND (200) -

MW-36 WG-BYN-042506-SS-09 4/25/2006 TBE ND (200) -

MW-37 MW-37 3/31/2006 EI ND (200) -

CRA 045136 (13) Byron Generating Station

TABLE 5.3 Page 3 of 3

SUMMARY

OF TRITIUM CONCENTRATIONS IN GROUNDWATER - FEBRUARY - APRIL 2006 FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Result Sample Location Sample Identification Sample Date QC Sample Laboratory Analyses Tritium (pCi/L) Error MW-37 GW-040606-NK-MW-37 4/6/2006 EI ND (200) -

MW-37 WG-BYN-042606-SS-33 4/26/2006 TBE ND (200) -

MW-39 MW-39 3/31/2006 EI ND (200) -

MW-39 GW-040606-NK-MW39 4/6/2006 EI ND (200) -

MW-39 WG-BYN-042606-SS-29 4/26/2006 TBE ND (200) -

PC-1B PC-1B 3/31/2006 EI ND (200) -

PC-1B GW-19232-040606-BW-PC-1B 4/6/2006 EI ND (200) -

PC-1B WG-BYN-042606-SS-23 4/26/2006 TBE ND (200) -

PC-1C PC-1C 3/31/2006 EI ND (200) -

PC-1C GW-040606-NK-PC-1C 4/6/2006 EI ND (200) -

PC-1C WG-BYN-042606-SS-21 4/26/2006 TBE ND (200) -

PC-2B PC-2B 3/31/2006 EI ND (200) -

PC-2B GW-19232-040606-BW-PC-2B 4/6/2006 EI ND (200) -

PC-2B WG-BYN-042506-SS-07 4/25/2006 TBE ND (200) -

PC-5B PC-5B 3/31/2006 EI ND (200) -

PC-5B PC-5B 3/31/2006 Duplicate (PC-5B) EI ND (200) -

PC-5B GW-19232-040606-BW-PC-5B 4/6/2006 EI ND (200) -

PC-5B WG-BYN-042506-SS-11 4/25/2006 TBE ND (200) -

PC-6B PC-6B 3/31/2006 EI ND (200) -

PC-6B GW-19232-040606-BW-PC-6B 4/6/2006 EI ND (200) -

PC-6B WG-BYN-042606-SS-17 4/26/2006 TBE ND (200) -

PC-6B WG-BYN-042606-SS-19 4/26/2006 Duplicate (SS-17) TBE ND (200) -

TW-13 GW-030806-KD-02 3/8/2006 EI ND (200) -

TW-13 GW-030806-KD-03 3/8/2006 Duplicate (KD-02) EI ND (200) -

TW-13 GW-19232-040606-BW-TW-13 4/6/2006 EI ND (200) -

TW-13 GW-19232-041206-EV-TW-13 4/12/2006 EI ND (200) -

TW-13 WG-BYN-042706-SS-39 4/27/2006 TBE ND (200) -

TW-13 WG-BYN-042706-SS-40 4/27/2006 Duplicate (SS-39) TBE 201 +/-110 TW-14 GW-19232-040606-BW-TW-14 4/6/2006 EI ND (200) -

TW-14 GW-19232-041106-EV-TW-14 4/12/2006 EI ND (200) -

TW-14 WG-BYN-042706-SS-37 4/27/2006 TBE ND (200) -

TW-15 GW-030806-KD-04 3/8/2006 EI ND (200) -

TW-15 GW-19232-040606-BW-TW-15 4/6/2006 EI ND (200) -

TW-15 GW-19232-041106-EV-TW-15 4/12/2006 EI ND (200) -

TW-15 WG-BYN-042706-SS-38 4/27/2006 TBE ND (200) -

Well 7 WG-BYN-042706-KD-45 4/27/2006 TBE ND (200) -

Well 7 WG-BYN-042706-KD-46 4/27/2006 Duplicate (KD-45) TBE ND (200) -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

QC - Quality Control NR - +/- value not reported.

CRA 045136 (13) Byron Generating Station

TABLE 5.4 Page 1 of 1

SUMMARY

OF TRITIUM CONCENTRATIONS IN WATER - RESIDENTIAL WATER SUPPLY WELLS FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Result Sample Location Sample Identification Sample Date Laboratory Analyses Tritium (pCi/L) Error ALEXANDER WELL ALEXANDER WELL 2/28/2006 EI ND (200) -

BLANCHARD WELL BLANCHARD RESIDENCE 2/16/2006 EI ND (200) -

BLANCHARD WELL BLANCHARD WELL 2/28/2006 EI ND (200) -

BRENDEL WELL BRENDEL WELL 2/28/2006 EI ND (200) -

DILLINGER WELL DILLINGER WELL 2/28/2006 EI ND (200) -

GORAL WELL GORAL WELL 2/28/2006 EI ND (200) -

LANDIS WELL LANDIS WELL 2/28/2006 EI ND (200) -

MASTNY WELL MASTNY WELL 2/28/2006 EI ND (200) -

STORZ WELL STORZ WELL 2/28/2006 EI ND (200) -

VANCKO WELL VANECKO RESIDENCE 2/16/2006 EI ND (200) -

VANCKO WELL VANCKO WELL 2/28/2006 EI ND (200) -

WILSON WELL WILSON WELL 2/28/2006 EI ND (200) -

Notes:

EI - Environmental, Inc.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

- - Non-detect value, +/- value not reported.

CRA 045136 (13) Byron Generating Station

TABLE 5.5 Page 1 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: AR-1 AR-1 AR-1 AR-1 AR-1 AR-1 AR-2 AR-2 Sample Identification: GW-19232-040606-BW-AR-1 Result GW-19232-041106-EV-AR-1 Result WG-BYN-042606-SS-25 Result GW-19232-041006-EV-AR-2 Result Sample Date: 4/6/2006 Error 4/12/2006 Error 4/26/2006 Error 4/10/2006 Error Laboratory: EI EI TBE EI Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) - ND (10) - ND (10) U* - ND (10) -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) U* - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) - ND (10) - ND (10) U* - ND (10) -

Strontium-89 pCi/L ND (2) - ND (2) - NA - ND (2) -

Strontium-89/90 (Total) pCi/L NA - NA - ND (2) - NA -

Strontium-90 pCi/L ND (2) - ND (2) - NA - ND (2) -

Zinc-65 pCi/L ND (30) - ND (30) - ND (30) U* - ND (30) -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - NA - RNI - NA -

Thorium-228 (1) pCi/L NA - NA - RNI - NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 2 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: AR-2 AR-2 AR-3 AR-3 AR-3 AR-3 AR-4 AR-4 Sample Identification: WG-BYN-042606-JK-22 Result GW-19232-041006-EV-AR-3 Result WG-BYN-042606-JK-20 Result GW-19232-041006-EV-AR-4 Result Sample Date: 4/26/2006 Error 4/10/2006 Error 4/26/2006 Error 4/10/2006 Error Laboratory: TBE EI TBE EI Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) U* - ND (10) - ND (10) U* - ND (10) -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) U* - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) U* - ND (10) - ND (10) U* - ND (10) -

Strontium-89 pCi/L NA - ND (2) - NA - ND (2) -

Strontium-89/90 (Total) pCi/L ND (2) - NA - ND (2) - NA -

Strontium-90 pCi/L NA - ND (2) - NA - ND (2) -

Zinc-65 pCi/L ND (30) U* - ND (30) - ND (30) U* - ND (30) -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L RNI - NA - RNI - NA -

Thorium-228 (1) pCi/L RNI - NA - RNI - NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 3 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: AR-4 AR-4 AR-5 AR-5 AR-5 AR-5 AR-5 AR-5 Sample Identification: WG-BYN-042706-SS-44 Result GW-040606-NK-AR-5 Result GW-19232-041106-EV-AR-5 Result WG-BYN-042706-SS-42 Result Sample Date: 4/27/2006 Error 4/6/2006 Error 4/11/2006 Error 4/27/2006 Error Laboratory: TBE EI EI TBE Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) U* - ND (10) - ND (10) - ND (10) U* -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

Strontium-89 pCi/L NA - ND (2) - ND (2) - NA -

Strontium-89/90 (Total) pCi/L ND (2) - NA - NA - ND (2) -

Strontium-90 pCi/L NA - ND (2) - ND (2) - NA -

Zinc-65 pCi/L ND (30) U* - ND (30) - ND (30) - ND (30) U* -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L RNI - NA - NA - RNI -

Thorium-228 (1) pCi/L RNI - NA - NA - 5.123 +/-2.552 Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 4 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: AR-6 AR-6 AR-6 AR-6 AR-6 AR-6 AR-7 AR-7 Sample Identification: GW-040606-NK-AR-6 Result GW-19232-041106-EV-AR-6 Result WG-BYN-042706-SS-41 Result GW-040506-NK-AR-7 Result Sample Date: 4/6/2006 Error 4/11/2006 Error 4/27/2006 Error 4/5/2006 Error Laboratory: EI EI TBE EI Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) - ND (10) - ND (10) U* - ND (10) -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) - ND (10) - ND (10) U* - ND (10) -

Strontium-89 pCi/L ND (2) - ND (2) - NA - ND (2) -

Strontium-89/90 (Total) pCi/L NA - NA - ND (2) - NA -

Strontium-90 pCi/L ND (2) - ND (2) - NA - ND (2) -

Zinc-65 pCi/L ND (30) - ND (30) - ND (30) U* - ND (30) -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - NA - RNI - NA -

Thorium-228 (1) pCi/L NA - NA - RNI - NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 5 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: AR-7 AR-7 AR-7 AR-7 AR-8 AR-8 AR-8 AR-8 AR-8 Sample Identification: GW-19232-041106-EV-AR-7 Result WG-BYN-042706-KD-32 Result GW-040506-NK-AR-8 Result GW-19232-041106-EV-AR-8 Result WG-BYN-042706-KD-30 Sample Date: 4/11/2006 Error 4/27/2006 Error 4/5/2006 Error 4/11/2006 Error 4/27/2006 Laboratory: EI TBE EI EI TBE Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) - ND (60)

Cesium-134 pCi/L ND (10) - ND (10) U* - ND (10) - ND (10) - ND (10) U*

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) - ND (18) - ND (18)

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) - ND (15)

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) - ND (15)

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) - ND (30)

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) - ND (15)

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) - ND (15)

Niobium-95 pCi/L ND (10) - ND (10) U* - ND (10) - ND (10) - ND (10) U*

Strontium-89 pCi/L ND (2) - NA - ND (2) - ND (2) - NA Strontium-89/90 (Total) pCi/L NA - ND (2) - NA - NA - ND (2)

Strontium-90 pCi/L ND (2) - NA - ND (2) - ND (2) - NA Zinc-65 pCi/L ND (30) - ND (30) U* - ND (30) - ND (30) - ND (30) U*

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) - ND (10)

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - RNI - NA - NA - RNI Thorium-228 (1) pCi/L NA - RNI - NA - NA - RNI Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 6 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: AR-8 AR-9 AR-9 AR-9 AR-9 AR-9 AR-9 AR-10 AR-10 Sample Identification: Result GW-040506-NK-AR-9 Result GW-19232-041106-EV-AR-9 Result WG-BYN-042706-KD-26 Result GW-19232-040606-BW-AR-10 Result Sample Date: Error 4/5/2006 Error 4/11/2006 Error 4/27/2006 Error 4/6/2006 Error Laboratory: EI EI TBE EI Analysis:

Target Radionuclides Units Barium-140 pCi/L - ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L - ND (10) - ND (10) - ND (10) U* - ND (10) -

Cesium-137 pCi/L - ND (18) - ND (18) - ND (18) - ND (18) -

Cobalt-58 pCi/L - ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L - ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L - ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L - ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L - ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L - ND (10) - ND (10) - ND (10) U* - ND (10) -

Strontium-89 pCi/L - ND (2) - ND (2) - NA - ND (2) -

Strontium-89/90 (Total) pCi/L - NA - NA - ND (2) - NA -

Strontium-90 pCi/L - ND (2) - ND (2) - NA - ND (2) -

Zinc-65 pCi/L - ND (30) - ND (30) - ND (30) U* - ND (30) -

Zirconium-95 pCi/L - ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L - NA - NA - RNI - NA -

Thorium-228 (1) pCi/L - NA - NA - RNI - NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 7 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: AR-10 AR-10 AR-10 AR-10 AR-11 AR-11 AR-11 AR-11 Sample Identification: GW-19232-041106-EV-AR-10 Result WG-BYN-042606-JK-24 Result GW-041806-KD-AR-11 Result WG-BYN-042606-SS-27 Result Sample Date: 4/12/2006 Error 4/26/2006 Error 4/18/2006 Error 4/26/2006 Error Laboratory: EI TBE EI TBE Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) - ND (10) U* - ND (10) - ND (10) U* -

Cesium-137 pCi/L ND (18) - ND (18) U* - ND (18) - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L 13.6 NR ND (10) U* - ND (10) - ND (10) -

Strontium-89 pCi/L ND (2) - NA - ND (2) - NA -

Strontium-89/90 (Total) pCi/L NA - ND (2) - NA - ND (2) -

Strontium-90 pCi/L ND (2) - NA - ND (2) - NA -

Zinc-65 pCi/L ND (30) - ND (30) U* - ND (30) - ND (30) U* -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - RNI - NA - RNI -

Thorium-228 (1) pCi/L NA - 6.173 +/-3.26 NA - RNI -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 8 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: CAR-1 CAR-1 CAR-1 CAR-1 CAR-1 CAR-1 CAR-2 CAR-2 Sample Identification: GW-19232-040606-BW-CAR-1 Result GW-19232-041106-EV-CAR-1 Result WG-BYN-042706-SS-36 Result GW-19232-040606-BW-CAR-2 Result Sample Date: 4/6/2006 Error 4/12/2006 Error 4/27/2006 Error 4/6/2006 Error Laboratory: EI EI TBE EI Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) - ND (10) - ND (10) U* - ND (10) -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) - ND (10) - ND (10) U* - ND (10) -

Strontium-89 pCi/L ND (2) - ND (2) - NA - ND (2) -

Strontium-89/90 (Total) pCi/L NA - NA - ND (2) - NA -

Strontium-90 pCi/L ND (2) - ND (2) - NA - ND (2) -

Zinc-65 pCi/L ND (30) - ND (30) - ND (30) U* - ND (30) -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - NA - RNI - NA -

Thorium-228 (1) pCi/L NA - NA - 6.113 +/-3.568 NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 9 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: CAR-2 CAR-2 CAR-2 CAR-2 CAR-2 CAR-2 CAR-3 CAR-3 Sample Identification: GW-19232-041106-EV-CAR-2 Result GW-19232-041106-EV-CAR-2 Result WG-BYN-042706-SS-47 Result GW-040506-NK-CAR-3 Result Sample Date: 4/12/2006 Error 4/12/2006 Error 4/27/2006 Error 4/5/2006 Error Duplicate Laboratory: EI EI TBE EI Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) - ND (10) - ND (10) U* - ND (10) -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) - ND (10) - ND (10) U* - ND (10) -

Strontium-89 pCi/L ND (2) - ND (2) - NA - ND (2) -

Strontium-89/90 (Total) pCi/L NA - NA - ND (2) - NA -

Strontium-90 pCi/L ND (2) - ND (2) - NA - ND (2) -

Zinc-65 pCi/L ND (30) - ND (30) - ND (30) U* - ND (30) -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - NA - RNI - NA -

Thorium-228 (1) pCi/L NA - NA - RNI - NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 10 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: CAR-3 CAR-3 CAR-3 CAR-3 GW-9 GW-9 TW-13 TW-13 Sample Identification: GW-19232-041106-EV-CAR-3 Result WG-BYN-042706-KD-28 Result WG-BYN-042806-KD-48 Result GW-19232-040606-BW-TW-13 Result Sample Date: 4/11/2006 Error 4/27/2006 Error 4/28/2006 Error 4/6/2006 Error Laboratory: EI TBE TBE EI Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) - ND (10) U* - ND (10) U* - ND (10) -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) - ND (10) U* - ND (10) U* - ND (10) -

Strontium-89 pCi/L ND (2) - NA - NA - ND (2) -

Strontium-89/90 (Total) pCi/L NA - ND (2) - ND (2) - NA -

Strontium-90 pCi/L ND (2) - NA - NA - ND (2) -

Zinc-65 pCi/L ND (30) - ND (30) U* - ND (30) U* - ND (30) -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - RNI - 40.44 +/-23.27 NA -

Thorium-228 (1) pCi/L NA - 6.427 +/-2.496 RNI - NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 11 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: TW-13 TW-13 TW-13 TW-13 TW-13 TW-13 TW-14 TW-14 Sample Identification: GW-19232-041206-EV-TW-13 Result WG-BYN-042706-SS-39 Result WG-BYN-042706-SS-40 Result GW-19232-040606-BW-TW-14 Result Sample Date: 4/12/2006 Error 4/27/2006 Error 4/27/2006 Error 4/6/2006 Error Duplicate Laboratory: EI TBE TBE EI Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) - ND (10) U* - ND (10) U* - ND (10) -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) - ND (10) U* - ND (10) U* - ND (10) -

Strontium-89 pCi/L ND (2) - NA - NA - ND (2) -

Strontium-89/90 (Total) pCi/L NA - ND (2) - ND (2) - NA -

Strontium-90 pCi/L ND (2) - NA - NA - ND (2) -

Zinc-65 pCi/L ND (30) - ND (30) U* - ND (30) U* - ND (30) -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - RNI - RNI - NA -

Thorium-228 (1) pCi/L NA - RNI - RNI - NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 12 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: TW-14 TW-14 TW-14 TW-14 TW-15 TW-15 TW-15 TW-15 Sample Identification: GW-19232-041106-EV-TW-14 Result WG-BYN-042706-SS-37 Result GW-19232-040606-BW-TW-15 Result GW-19232-041106-EV-TW-15 Result Sample Date: 4/12/2006 Error 4/27/2006 Error 4/6/2006 Error 4/12/2006 Error Laboratory: EI TBE EI EI Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) - ND (10) U* - ND (10) - ND (10) -

Cesium-137 pCi/L ND (18) - ND (18) - ND (18) - ND (18) -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) - ND (10) U* - ND (10) - ND (10) -

Strontium-89 pCi/L ND (2) - NA - ND (2) - ND (2) -

Strontium-89/90 (Total) pCi/L NA - ND (2) - NA - NA -

Strontium-90 pCi/L ND (2) - NA - ND (2) - ND (2) -

Zinc-65 pCi/L ND (30) - ND (30) U* - ND (30) - ND (30) -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L NA - RNI - NA - NA -

Thorium-228 (1) pCi/L NA - RNI - NA - NA -

Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

TABLE 5.5 Page 13 of 13

SUMMARY

OF RADIONUCLIDE CONCENTRATIONS IN GROUNDWATER FLEETWIDE ASSESSMENT BYRON GENERATING STATION BYRON, ILLINOIS Sample Location: TW-15 TW-15 Well 7 Well 7 Well 7 Well 7 Sample Identification: WG-BYN-042706-SS-38 Result WG-BYN-042706-KD-45 Result WG-BYN-042706-KD-46 Result Sample Date: 4/27/2006 Error 4/27/2006 Error 4/27/2006 Error Duplicate Laboratory: TBE TBE TBE Analysis:

Target Radionuclides Units Barium-140 pCi/L ND (60) - ND (60) - ND (60) -

Cesium-134 pCi/L ND (10) U* - ND (10) U* - ND (10) U* -

Cesium-137 pCi/L ND (18) - ND (18) U* - ND (18) U* -

Cobalt-58 pCi/L ND (15) - ND (15) - ND (15) U* -

Cobalt-60 pCi/L ND (15) - ND (15) - ND (15) -

Iron-59 pCi/L ND (30) - ND (30) - ND (30) -

Lanthanum-140 pCi/L ND (15) - ND (15) U* - ND (15) -

Manganese-54 pCi/L ND (15) - ND (15) - ND (15) -

Niobium-95 pCi/L ND (10) U* - ND (10) U* - ND (10) U* -

Strontium-89 pCi/L NA - NA - NA -

Strontium-89/90 (Total) pCi/L ND (2) - ND (2) - ND (2) -

Strontium-90 pCi/L NA - NA - NA -

Zinc-65 pCi/L ND (30) U* - ND (30) U* - ND (30) U* -

Zirconium-95 pCi/L ND (10) - ND (10) - ND (10) -

(1)

Non-Target Radionuclides Potassium-40 (1) pCi/L RNI - RNI - RNI Thorium-228 (1) pCi/L RNI - RNI - RNI Notes:

EI - Environmental, Inc.

TBE - Teledyne Brown Engineering, Inc.

(1) - These non-targeted radionuclides are included in this table but excluded from the discussion in this report. These radionuclides were either a) naturally occurring and thus not produced by the Station, or b) could be definitively evaluated as being naturally occurring due to the lack of presence of other radionuclides which would otherwise indicate the potential of production from the Station.

RNI- Radionuclide Not Identified during analysis.

NA - Data not available or not analyzed.

ND ( ) - Non-detect; value in parentheses is the LLD.

LLD - Lower limit of detection.

U* - Compound/Analyte not detected.

Peak not identified, but forced activity concentration exceeds Minimum Detectable Concentration and 3 sigma.

- - Non-detect value, +/- value not reported.

q018AI-XT2-WG WS-Historical-37-TH-RADIO CRA 45136 (13) Byron Generating Station 7/13/2006

Revision 0 APPENDIX A WATER SUPPLY WELL INFORMATION 045136 (13) Byron Generating Station

0 1000 2500ft STATION SOURCE: USGS QUADRANGLE MAP; STILLMAN VALLEY, ILLINOIS (1976)

OREGON, ILLINOIS (1983)

LEGEND APPROXIMATE WATER SUPPLY WELL LOCATION figure A.1 WATER SUPPLY WELL LOCATIONS BYRON GENERATING STATION EXELON GENERATION COMPANY, LLC 45136-21(013)GN-CO001 SEP 08/2006

Revision 0 APPENDIX B MONITORING WELL STRATIGRAPHIC AND INSTRUMENTATION LOGS 045136 (13) Byron Generating Station

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-1 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 23, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE SP SAND (FILL) - trace of limestone gravel, Concrete medium grain, brown, dry 2

4" Borehole 4

Cement/Bentonite Grout 6

8 END OF OVERBURDEN HOLE @ 9.0ft BGS 10 12 14 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (BEDROCK) Page 2 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-1 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 23, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER CORE DEPTH DEPTH STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS RUN RQD %

NUMBER RECOVERY %

9.00 WEATHERED DOLOMITE - fissured, fractured, 10 light brown, wet 2" PVC Well Casing 12 14 16 18 20 22 24 26 28 30 Cement/Bentonite Grout 32 34 36 38 BEDROCK LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 40 42 44 46 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (BEDROCK) Page 3 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-1 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 23, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER CORE DEPTH DEPTH STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS RUN RQD %

NUMBER RECOVERY %

50 52 54 2" PVC Well Screen 56 58 60 Sand Pack 62 64 66 68 70 70.00 END OF BOREHOLE @ 70.0ft BGS WELL DETAILS Screened interval:

72 50.00 to 70.00ft BGS Length: 20ft Diameter: 2in 74 Slot Size: 0.010 Material: PVC Sand Pack:

76 47.00 to 70.00ft BGS Material: #2 Sand 78 BEDROCK LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 80 82 84 86 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-10 PROJECT NUMBER: 19232-21 DATE COMPLETED: April 5, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA/AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE UNCONSOLIDATED SEDIMENTS Concrete 2

4 Cement/Bentonite Grout 6

8 2" PVC Well Casing 10 9" Borehole from 0-19' 12 14 15.00 LIMESTONE - weathered 16 Bentonite Chips 18

- competent rock at 19.0ft BGS 4" Borehole from 19-29' 20 2" PVC Well Screen 22 Sand Pack 24 26 28 29.00 END OF BOREHOLE @ 29.0ft BGS OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 WELL DETAILS 30 Screened interval:

19.00 to 29.00ft BGS Length: 10ft 32 Diameter: 2in Slot Size: 0.010 Material: PVC 34 Sand Pack:

17.00 to 29.00ft BGS Material: Sand 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 4 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-11 PROJECT NUMBER: 19232-21 DATE COMPLETED: April 11, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: E. VARNAS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE UNCONSOLIDATED SEDIMENTS Concrete 2 6" Borehole from 0-8' 4

Cement/Bentonite Grout 6

8 8.00 4" Borehole BEDROCK - gray limestone from 8-150.5' 10 2" PVC Well Casing 12 14 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 4 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-11 PROJECT NUMBER: 19232-21 DATE COMPLETED: April 11, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: E. VARNAS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 42 44 46 48 50 4" Borehole from 8-150.5' 52 54 56 58 60 62 64 66 68 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 70 - some red color at 70.0ft BGS 72 74 - gray color at 74.0ft BGS 76 78 - red color at 78.0ft BGS NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 3 of 4 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-11 PROJECT NUMBER: 19232-21 DATE COMPLETED: April 11, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: E. VARNAS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 82 84 86 88 90 4" Borehole from 8-150.5' 92 94 96 98 100 102 104 106 - 1' of gray color at 106.0ft BGS 108 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 110 112 114 116 118 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 4 of 4 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-11 PROJECT NUMBER: 19232-21 DATE COMPLETED: April 11, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: E. VARNAS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 122 124 126 128 130 132 134 Bentonite Chips 136 138 4" Borehole from 8-150.5' 140 2" PVC Well Screen 142 Sand Pack 144 146 148 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 150 150.00 SHALE 150.50 END OF BOREHOLE @ 150.5ft BGS WELL DETAILS 152 Screened interval:

139.50 to 149.50ft BGS Length: 10ft 154 Diameter: 2in Slot Size: 0.010 Material: PVC 156 Sand Pack:

136.00 to 150.50ft BGS Material: Sand 158 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-2 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 21, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE SM SILTY SAND - with fine gravel, compact, fine Concrete grained, poorly graded, brown, moist 2

4 Cement/Bentonite Grout 6

6" Borehole from 0-10' 8

10 10.00 2" PVC Well DOLOSTONE - fissured, fractured, light brown Casing 12 14 16 4" Borehole from 10-81' 18 20 END OF OVERBURDEN HOLE @ 20.0ft BGS 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (BEDROCK) Page 2 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-2 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 21, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER CORE DEPTH DEPTH STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS RUN RQD %

NUMBER RECOVERY %

20 22 24 26 28 30 32 34 36 38 4" Borehole from 10-81' 40 42 44 46 48 BEDROCK LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 50 52 54 56 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (BEDROCK) Page 3 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-2 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 21, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER CORE DEPTH DEPTH STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS RUN RQD %

NUMBER RECOVERY %

60 62 64

- wet at 65.0ft BGS 66 68 4" Borehole from 10-81' 70 72 2" PVC Well Screen 74

- wet at 75.0ft BGS Sand Pack 76 78 80 81.00 END OF BOREHOLE @ 81.0ft BGS WELL DETAILS 82 Screened interval:

71.00 to 81.00ft BGS Length: 10ft 84 Diameter: 2in Slot Size: 0.010 Material: PVC 86 Sand Pack:

68.00 to 81.00ft BGS Material: #2 Sand 88 BEDROCK LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 90 92 94 96 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-3 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 22, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE SM SILTY SAND - with fine gravel, compact, fine Concrete grained, poorly graded, brown, moist 2

4" Borehole 4

Cement/Bentonite Grout 6

8 2" PVC Well Casing 10 END OF OVERBURDEN HOLE @ 11.0ft BGS 12 14 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (BEDROCK) Page 2 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-3 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 22, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER CORE DEPTH DEPTH STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS RUN RQD %

NUMBER RECOVERY %

11.00 DOLOSTONE - fissured, fractured, light brown 12 14 16 18 20 22 24 4" Borehole 26 28 30 32 34 36 38 40 BEDROCK LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 42 44 46 48 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (BEDROCK) Page 3 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-3 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 22, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: SONIC LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: S. POOLER CORE DEPTH DEPTH STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS RUN RQD %

NUMBER RECOVERY %

52 Cement/Bentonite Grout 54 56 58 4" Borehole 60 62 2" PVC Well Screen 64 Sand Pack

- wet at 65.0ft BGS 66 68 70 71.00 END OF BOREHOLE @ 71.0ft BGS WELL DETAILS 72 Screened interval:

60.00 to 70.00ft BGS Length: 10ft 74 Diameter: 2in Slot Size: 0.010 Material: PVC 76 Sand Pack:

57.00 to 71.00ft BGS Material: #2 Sand 78 80 BEDROCK LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 82 84 86 88 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-4 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 24, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: N. KUHL DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE UNCONSOLIDATED SEDIMENTS Concrete (see logs for TW-7 and TW-8) 2 Bentonite Grout 4

2" PVC Well Casing 6

6" Borehole from 0-12' 8 8.00 BEDROCK 10 12 - competent rock at 12.0ft BGS 14 16 18 4" Borehole from 12-121.5 20 22 24 26 28 30 32 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 34 36 38 40 42 44 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-4 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 24, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: N. KUHL DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 46 48 50 Cement/Bentonite Grout 52 4" Borehole from 12-121.5 54 56 58 60 62 64 66 68 70 72 74 76 78 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 80 82 84 86 88 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 3 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-4 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 24, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: N. KUHL DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 92 94 Bentonite Chips 96 4" Borehole 98 from 12-121.5 100 2" PVC Well Screen 102 Sand Pack 104 106 108 110 112 114 116 118 120 121.50 122 END OF BOREHOLE @ 121.5ft BGS WELL DETAILS Screened interval:

OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 124 99.50 to 119.50ft BGS Length: 20ft Diameter: 2in 126 Slot Size: 0.010 Material: PVC Sand Pack:

128 95.50 to 121.50ft BGS Material: Sand 130 132 134 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-5 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 23, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: N. KUHL DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE UNCONSOLIDATED SEDIMENTS Concrete (see logs for TW-9 and TW-10) 2 3.50 4 BEDROCK - weathered, gray limestone Cement/Bentonite Grout 6

6" Borehole from 0-12' 8

10 2" PVC Well Casing 12 - competent rock at 12.0ft BGS 14 16 18 20 4" Borehole from 12-122' 22 24 26 28 30 32 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 34 36 38 40 42 44 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-5 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 23, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: N. KUHL DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 46 48 50 52 54 56 58 60 4" Borehole from 12-122' 62 - gray-brown at 62.0ft BGS 64 66 68 70 72 74 76 78 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 80 82 84 86 88 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 3 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-5 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 23, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: N. KUHL DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 92 94 96 Bentonite Chips 98 100 4" Borehole from 12-122' 102 104 2" PVC Well Screen 106 Sand Pack 108 110 112 114 116 118 120 122 122.00 END OF BOREHOLE @ 122.0ft BGS WELL DETAILS OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 Screened interval:

124 102.00 to 122.00ft BGS Length: 20ft 126 Diameter: 2in Slot Size: 0.010 Material: PVC 128 Sand Pack:

98.00 to 122.00ft BGS Material: #6 Sand 130 132 134 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-6 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 21, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: E. VARNAS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE UNCONSOLIDATED SEDIMENTS Concrete (see logs for TW-11 and TW-12) 2 4

Cement/Bentonite Grout 6

8 8.00 6" Borehole BEDROCK from 0-12' 10 2" PVC Well Casing 12 - competent rock at 12.0ft BGS 14 16 18 20 4" Borehole from 12-122' 22 24 26 28 30 32 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 34 36 38 40 42 44 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-6 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 21, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: E. VARNAS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 46 48 50 52 54 56 58 4" Borehole from 12-122' 60 62 64 66 68 70 72 74 Cement/Bentonite Grout 76 78 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 80 82 Bentonite Chips 84 86 88 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 3 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-6 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 21, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: E. VARNAS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 92 4" Borehole from 12-122' 94 96 2" PVC Well Screen 98 Sand Pack 100 102 104 106 108 110 112 114 116 118 120 122 122.00 END OF BOREHOLE @ 122.0ft BGS WELL DETAILS OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 Screened interval:

124 95.00 to 115.00ft BGS Length: 20ft 126 Diameter: 2in Slot Size: 0.010 Material: PVC 128 Sand Pack:

85.00 to 122.00ft BGS Material: #6 Sand 130 132 134 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-7 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE SP SAND/GRAVEL FILL Concrete 2

9" Borehole from 0-20' 4

6 8 Cement/Bentonite Grout 10 2" PVC Well Casing 12 14 15.00 SC CLAYEY SAND 16 17.00 BEDROCK LIMESTONE - weathered 18 20 - competent rock at 20.0ft BGS 4" Borehole from 20-113' 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-7 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 42 44 46 48 50 52 54 56 58 60 - occasional sand pockets from 60-79' at 60.0ft BGS 62 64 66 68 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 70 72 74 76 78 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 3 of 3 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-7 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 82 84 86 88 90 92 94 96 98 100 Bentonite Chips 102 104 2" PVC Well Screen 106 Sand Pack 108 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 110 112 113.00 END OF BOREHOLE @ 113.0ft BGS WELL DETAILS 114 Screened interval:

102.00 to 113.00ft BGS Length: 11ft 116 Diameter: 2in Slot Size: 0.010 Material: PVC 118 Sand Pack:

100.00 to 113.00ft BGS Material: #5 Sand NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-8 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 31, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA/AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE GPS SAND/GRAVEL (FILL) Concrete 2 2.00 LIMESTONE - weathered 9" Borehole from 0-5' 4

- competent rock at 5.0ft BGS 4" Borehole from 5-53' 6

8 Cement/Bentonite Grout 10 2" PVC Well Casing 12 14 16 18 20 22 24 26 Bentonite Chips 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 2" PVC Well Screen 34 Sand Pack 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-8 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 31, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA/AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 42 44 4" Borehole from 5-53' 46 48 50 52 53.00 END OF BOREHOLE @ 53.0ft BGS WELL DETAILS 54 Screened interval:

30.00 to 50.00ft BGS Length: 20ft 56 Diameter: 2in Slot Size: 0.010 Material: PVC 58 Sand Pack:

28.00 to 53.00ft BGS Material: Sand 60 62 64 66 68 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 70 72 74 76 78 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-9 PROJECT NUMBER: 19232-21 DATE COMPLETED: April 4, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA/AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE UNCONSOLIDATED SEDIMENTS Concrete 2

4 Cement/Bentonite Grout 6

8 9" Borehole from 0-25' 10 2" PVC Well Casing 12 14 16 18 20 20.00 BEDROCK - weathered 22 24

- competent rock at 25.0ft BGS 4" Borehole from 25-68' 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: AR-9 PROJECT NUMBER: 19232-21 DATE COMPLETED: April 4, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA/AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 42 44 46 4" Borehole from 25-68' 48 50 52 Bentonite Chips 54 56 2" PVC Well Screen 58 Sand Pack 60 62 64 66 68 68.00 END OF BOREHOLE @ 68.0ft BGS WELL DETAILS Screened interval:

OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 70 55.50 to 65.50ft BGS Length: 10ft Diameter: 2in 72 Slot Size: 0.010 Material: PVC Sand Pack:

74 54.00 to 68.00ft BGS Material: #6 Sand 76 78 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: CAR-1 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 21, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE SP SAND - fine grained, trace medium sand, poorly graded, medium brown, moist Concrete 2

4 6

8 8" Borehole 10

- some coarse sand, dark brown at 11.2ft BGS 12 14

- trace fine gravel at 15.0ft BGS 16 18 20 - some fine gravel at 20.0ft BGS Cement/Bentonite 22 Grout 24 26

- wet at 27.0ft BGS 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 2" PVC Well Casing NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: CAR-1 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 21, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 42 Bentonite Chips 44 8" Borehole 46 2" PVC Well Screen 48 Sand Pack 50 - dense at 50.0ft BGS 52 54 55.00 END OF BOREHOLE @ 55.0ft BGS WELL DETAILS 56 Screened interval:

45.00 to 55.00ft BGS Length: 10ft 58 Diameter: 2in Slot Size: 0.010 Material: PVC 60 Sand Pack:

43.00 to 55.00ft BGS Material: Sand 62 64 66 68 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 70 72 74 76 78 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: CAR-2 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 22, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA/4" ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE SP SAND Concrete 2

4 6

8 9" Borehole 10 2" PVC Well Casing Cement/Bentonite Grout 12 14 16 18 20 END OF OVERBURDEN HOLE @ 20.0ft BGS 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (BEDROCK) Page 2 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: CAR-2 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 22, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: 4-1/4" HSA/4" ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS CORE DEPTH DEPTH STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS RUN RQD %

NUMBER RECOVERY %

20 20.00 8" Borehole LIMESTONE/DOLOMITE (highly weathered) - thinly from 0-20' bedded, trace fine sand pockets, white/beige, dry, calcareous nodules 22 Bentonite Chips 1 4.6 24 26 2" PVC Well Screen 28 4" Borehole from 20-36.5' 2 100 30 Sand Pack 32 34 3 100 36 36.50 END OF BOREHOLE @ 36.5ft BGS WELL DETAILS 38 Screened interval:

25.00 to 35.00ft BGS Length: 10ft 40 Diameter: 2in Slot Size: 0.010 Material: PVC 42 Sand Pack:

23.00 to 36.50ft BGS Material: Sand 44 46 48 BEDROCK LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 50 52 54 56 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: CAR-3 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 29, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE UNCONSOLIDATED SEDIMENTS Concrete 2

4 6

8 10 12 14 Cement/Bentonite Grout 16 18 19.00 WEATHERED LIMESTONE BEDROCK 20 9" Borehole from 0-25' 22 24 2" PVC Well Casing 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 Bentonite Chips NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 2 of 2 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: CAR-3 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 29, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: AIR ROTARY LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: B. WILLIAMS DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Monitoring Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE 4" Borehole 42 from 25-63' 44 2" PVC Well Screen 46 Sand Pack 48 50 52 54 56 58 60 62 63.00 END OF BOREHOLE @ 63.0ft BGS WELL DETAILS 64 Screened interval:

43.00 to 63.00ft BGS Length: 20ft 66 Diameter: 2in Slot Size: 0.010 Material: PVC 68 Sand Pack:

40.00 to 63.00ft BGS OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 Material: #5 Sand 70 72 74 76 78 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-1 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 27, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite SP SAND (FILL) - trace limestone gravel, medium Chips 2 grain, brown, dry 2" PVC Well Casing 1GP 0.0 8" Borehole 4

2" PVC Well Screen 6

Sand Pack 2GP 0.0 8 8.00 LIMESTONE - sandy and silty, weathered, brown, dry 9.00 WELL DETAILS 10 - AUGER REFUSAL at 8.5ft BGS Screened interval:

- GEOPROBE REFUSAL at 9.0ft BGS 3.50 to 8.50ft BGS END OF BOREHOLE @ 9.0ft BGS Length: 5ft 12 Diameter: 2in Slot Size: 0.010 Material: PVC 14 Sand Pack:

2.50 to 8.50ft BGS Material: Sand 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-10 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 1, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL Bentonite 1.00 Chips CL CLAY (FILL) - sandy, low plasticity, brown, 2" PVC Well 2 moist Casing 8" Borehole 1GP 0.0 3.00 SP SAND - medium grain, brown, dry 4 2" PVC Well Screen 6 Sand Pack 2GP 0.0 7.00 WEATHERED LIMESTONE - sandy, silty, brown, 8 dry 8.00 WELL DETAILS

- AUGER REFUSAL at 7.5ft BGS Screened interval:

- GEOPROBE REFUSAL at 8.0ft BGS 2.50 to 7.50ft BGS 10 END OF BOREHOLE @ 8.0ft BGS Length: 5ft Diameter: 2in Slot Size: 0.010 12 Material: PVC Sand Pack:

1.50 to 7.50ft BGS 14 Material: Sand 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-11 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 1, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, brown, Chips 2 moist 1GP 0.0 2" PVC Well Casing 4

4.50 8" Borehole SP SAND - medium grained, brown, dry 6

2" PVC Well 2GP 0.0 Screen 8

9.00 Sand Pack WEATHERED LIMESTONE - sandy, silty, brown, 10 dry 10.00

- GEOPROBE REFUSAL at 9.0ft BGS WELL DETAILS

- AUGER REFUSAL at 10.0ft BGS Screened interval:

12 END OF BOREHOLE @ 10.0ft BGS 5.00 to 10.00ft BGS Length: 5ft Diameter: 2in 14 Slot Size: 0.010 Material: PVC Sand Pack:

16 4.00 to 10.00ft BGS Material: Sand 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-12 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 1, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, moist Chips 2

1GP 0.0 2" PVC Well Casing 4

4.50 SP SAND - medium grained, brown, dry 6 8" Borehole 2GP 0.0 8

9.00 2" PVC Well WEATHERED LIMESTONE - sandy, silty, brown, Screen 10 dry

- GEOPROBE REFUSAL at 9.0ft BGS Sand Pack 12 - AUGER REFUSAL at 12.0ft BGS 12.00 END OF BOREHOLE @ 12.0ft BGS WELL DETAILS Screened interval:

14 7.00 to 12.00ft BGS Length: 5ft Diameter: 2in 16 Slot Size: 0.010 Material: PVC Sand Pack:

18 5.50 to 12.00ft BGS Material: Sand 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-13 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 1, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 CL CLAY - sandy, low plasticity, brown, moist 2

1GP 0.0 Bentonite Chips 4 4.00 SP SAND - medium grain, brown, dry 2" PVC Well Casing 6

2GP 0.0 8 8.00 GC CLAYEY GRAVEL (limestone) - sandy, orange/brown, dry 10 10.00 SP SAND - medium grain, brown, dry 3GP 0.0 12 - GEOPROBE REFUSAL at 12.0ft BGS 8" Borehole 14 2" PVC Well Screen

- saturated at 15.0ft BGS 16 Sand Pack 18 - AUGER REFUSAL at 18.0ft BGS 18.00 END OF BOREHOLE @ 18.0ft BGS WELL DETAILS Screened interval:

20 13.00 to 18.00ft BGS Length: 5ft Diameter: 2in 22 Slot Size: 0.010 Material: PVC Sand Pack:

24 11.00 to 18.00ft BGS Material: Sand 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE WATER FOUND

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-14 PROJECT NUMBER: 19232-21 DATE COMPLETED: April 5, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL Concrete 1.00 CL CLAY - sandy, low plasticity, brown, moist 2

1GP 0.0 4 4.00 SP SAND - medium grained, brown, dry 6

2GP 0.0 8

- moist at 8.5ft BGS 10 Cement/Bentonite Grout 12 3GP 0.0 13.00 GC CLAYEY GRAVEL (limestone) - sandy, 14 orange/brown, moist 2" PVC Well Casing 16 4GP 0.0 18 20

- interbedded layers of sand at 21.0ft BGS Bentonite Chips 22 5GP 0.0 9" Borehole 24 - weathered sandstone pieces mixed in medium grained, green/gray at 24.0ft BGS

- GEOPROBE REFUSAL at 25.0ft BGS 26 2" PVC Well Screen 28 Sand Pack 30 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 32 34 34.00 END OF BOREHOLE @ 34.0ft BGS WELL DETAILS Screened interval:

36 24.00 to 34.00ft BGS Length: 10ft Diameter: 2in 38 Slot Size: 0.010 Material: PVC 40 Sand Pack:

22.00 to 34.00ft BGS Material: Sand 42 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-15 PROJECT NUMBER: 19232-21 DATE COMPLETED: March 1, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 SP SAND - medium grained, brown, moist 2

1GP 0.0 4

Bentonite Chips 6

2GP 0.0 8

10 2" PVC Well Casing 12 3GP 0.0 14 - increasing clay with depth at 14.0ft BGS 16 16.00 CI CLAY - silty, medium plasticity, brown, moist 4GP 0.0 18 18.00 SP SAND - medium grained, brown, moist 20 22 5GP 0.0 8" Borehole 24 25.00 GC CLAYEY GRAVEL - sandy, light brown, 26 saturated 2" PVC Well Screen Sand Pack 6GP 0.0 28

- GEOPROBE REFUSAL at 29.0ft BGS OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 WELL DETAILS 30 - AUGER REFUSAL at 30.0ft BGS 30.00 Screened interval:

END OF BOREHOLE @ 30.0ft BGS 24.00 to 29.00ft BGS Length: 5ft 32 Diameter: 2in Slot Size: 0.010 Material: PVC 34 Sand Pack:

22.00 to 29.00ft BGS Material: Sand 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-2 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 27, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL Bentonite 1.00 Chips SP SAND (FILL) - trace of limestone gravel, 2" PVC Well 2 medium grain, brown, dry Casing 8" Borehole 1GP 0.0 2" PVC Well Screen 4 Sand Pack 6

- AUGER REFUSAL at 7.0ft BGS 2GP 0.0 WELL DETAILS 8 8.00 WEATHERED LIMESTONE - sandy, silty, brown, Screened interval:

dry 9.00 2.00 to 7.00ft BGS 10 - GEOPROBE REFUSAL at 9.0ft BGS Length: 5ft END OF BOREHOLE @ 9.0ft BGS Diameter: 2in Slot Size: 0.010 Material: PVC 12 Sand Pack:

1.50 to 7.00ft BGS Material: Sand 14 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-3 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, brown, Chips 2 moist 1GP 0.0 2" PVC Well Casing 4 4.00 SP SAND - medium grain, brown, dry 8" Borehole 6

2" PVC Well 2GP 0.0 Screen 8

- moist at 8.5ft BGS 9.00 Sand Pack WEATHERED LIMESTONE - sandy, silty, brown, 10 dry 10.50

- GEOPROBE REFUSAL at 9.0ft BGS WELL DETAILS

- AUGER REFUSAL at 10.5ft BGS 12 Screened interval:

END OF BOREHOLE @ 10.5ft BGS 5.50 to 10.50ft BGS Length: 5ft 14 Diameter: 2in Slot Size: 0.010 Material: PVC 16 Sand Pack:

4.50 to 10.50ft BGS Material: Sand 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-4 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, brown, Chips 2 moist 1GP 0.0 2" PVC Well Casing 4 4.00 SP SAND - medium grain, brown, dry 8" Borehole 6

2" PVC Well 2GP 0.0 Screen 8

9.00 Sand Pack WEATHERED LIMESTONE - sandy, silty, brown, 10 dry 10.50

- GEOPROBE REFUSAL at 9.0ft BGS WELL DETAILS

- AUGER REFUSAL at 10.5ft BGS 12 Screened interval:

END OF BOREHOLE @ 10.5ft BGS 5.50 to 10.50ft BGS Length: 5ft 14 Diameter: 2in Slot Size: 0.010 Material: PVC 16 Sand Pack:

4.50 to 10.50ft BGS Material: Sand 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-5 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, brown, Chips 2 moist 2" PVC Well Casing 1GP 0.0 8" Borehole 4 4.00 2" PVC Well SP SAND - medium grain, brown, dry Screen Sand Pack 6

2GP 0.0 8 - GEOPROBE REFUSAL at 8.0ft BGS 8.00

- AUGER REFUSAL at 8.0ft BGS WELL DETAILS END OF BOREHOLE @ 8.0ft BGS Screened interval:

10 3.00 to 8.00ft BGS Length: 5ft Diameter: 2in 12 Slot Size: 0.010 Material: PVC Sand Pack:

14 2.00 to 8.00ft BGS Material: Sand 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-6 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, brown, Chips 2 moist 2" PVC Well Casing 1GP 0.0 8" Borehole 4 4.00 SP SAND - medium grain, brown, dry 2" PVC Well Screen 6

2GP 0.0 Sand Pack 8

- GEOPROBE REFUSAL at 8.5ft BGS 8.50

- AUGER REFUSAL at 8.5ft BGS WELL DETAILS 10 END OF BOREHOLE @ 8.5ft BGS Screened interval:

3.50 to 8.50ft BGS Length: 5ft 12 Diameter: 2in Slot Size: 0.010 Material: PVC 14 Sand Pack:

2.50 to 8.50ft BGS Material: Sand 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-7 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, brown, Chips 2 moist 1GP 0.0 2" PVC Well 3.50 Casing 4 SP SAND, medium grain, brown, dry 8" Borehole 6

2" PVC Well 2GP 0.0 Screen 8

Sand Pack 9.50 10 CL CLAY - sandy, low plasticity, brown, moist

- GEOPROBE REFUSAL at 9.5ft BGS 11.00

- AUGER REFUSAL at 11.0ft BGS WELL DETAILS 12 END OF BOREHOLE @ 11.0ft BGS Screened interval:

6.00 to 11.00ft BGS Length: 5ft 14 Diameter: 2in Slot Size: 0.010 Material: PVC 16 Sand Pack:

5.00 to 11.00ft BGS Material: Sand 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-8 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, brown, Chips 2 moist 1GP 0.0 2" PVC Well 3.50 Casing 4 SP SAND - medium grain, brown, dry 6

8" Borehole 2GP 0.0 8 2" PVC Well Screen 9.50 10 CL CLAY - sandy, low plasticity, brown, moist Sand Pack

- GEOPROBE REFUSAL at 9.5ft BGS 12 - AUGER REFUSAL at 12.0ft BGS 12.00 END OF BOREHOLE @ 12.0ft BGS WELL DETAILS Screened interval:

14 7.00 to 12.00ft BGS Length: 5ft Diameter: 2in 16 Slot Size: 0.010 Material: PVC Sand Pack:

18 6.00 to 12.00ft BGS Material: Sand 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

STRATIGRAPHIC AND INSTRUMENTATION LOG (OVERBURDEN) Page 1 of 1 PROJECT NAME: EXELON-BYRON HOLE DESIGNATION: TW-9 PROJECT NUMBER: 19232-21 DATE COMPLETED: February 28, 2006 CLIENT: EXELON GENERATION COMPANY LLC DRILLING METHOD: GEOPROBE/4-1/4" HSA LOCATION: BYRON, ILLINOIS FIELD PERSONNEL: R. AAMOT DEPTH DEPTH SAMPLE STRATIGRAPHIC DESCRIPTION & REMARKS Temporary Well ft BGS ft BGS NUMBER INTERVAL REC (%) 'N' VALUE PID (ppm)

TOPSOIL 1.00 Bentonite CL CLAY (FILL) - sandy, low plasticity, brown, Chips 2 moist 2" PVC Well Casing 1GP 0.0 3.00 8" Borehole SP SAND - medium grain, brown, dry 4 2" PVC Well Screen 6 Sand Pack 2GP 0.0 7.00 WEATHERED LIMESTONE - sandy, silty, brown, 8 dry 8.00

- GEOPROBE REFUSAL at 8.0ft BGS WELL DETAILS

- AUGER REFUSAL at 8.0ft BGS Screened interval:

10 END OF BOREHOLE @ 8.0ft BGS 3.00 to 8.00ft BGS Length: 5ft Diameter: 2in 12 Slot Size: 0.010 Material: PVC Sand Pack:

14 2.00 to 8.00ft BGS Material: Sand 16 18 20 22 24 26 28 OVERBURDEN LOG 19232-21.GPJ CRA_CORP.GDT 5/29/06 30 32 34 36 38 NOTES: MEASURING POINT ELEVATIONS MAY CHANGE; REFER TO CURRENT ELEVATION TABLE

Revision 0 APPENDIX C QUALITY ASSURANCE PROGRAM C.1 ENVIRONMENTAL, INC.

C.2 TELEDYNE BROWN ENGINEERING, INC.

045136 (13) Byron Generating Station

Revision 0 C.1 ENVIRONMENTAL, INC.

045136 (13) Byron Generating Station

Revision 0 C.2 TELEDYNE BROWN ENGINEERING, INC.

045136 (13) Byron Generating Station

TABLE OF CONTENTS Section Title Page 1.0 KNOXVILLE QAM SECTION INTRODUCTION 7 2.0 QUALITY SYSTEM 10 2.1 Policy 10 2.2 Quality System Structure 10 2.3 Quality System Objectives 10 2.4 Personnel Orientation, Training, and Qualification 11 3.0 ORGANIZATION, AUTHORITY, AND RESPONSIBILITY 12 4.0 PERSONNEL ORIENTATION, DATA INTEGRITY, TRAINING, AND QUALIFICATION 13 4.1 Orientation 13 4.2 Data Integrity 13 4.3 Training 13 4.4 Qualification 13 4.5 Records 13 5.0 CUSTOMER INTERFACES 14 5.1 Interface Personnel 14 5.2 Bid Requests and Tenders 14 5.3 Contracts 14 5.4 TBEs Expectation of Customers 14 5.5 Customer Satisfaction 15 5.5.1 Customer Complaints 15 5.5.2 Customer Confidentiality 15 6.0 DOCUMENTATION GENERATION AND CONTROL 16 6.1 General 16 6.2 New Documentation 16 6.3 Documentation Changes 16 Page 2 of 32

TABLE OF CONTENTS - Continued 6.4 Documentation Lists and Distributions 16 6.5 Other Documentation 16 6.6 Documentation Reviews 16 7.0 DESIGN OF LABORATORY CONTROLS 17 7.1 General 17 7.2 Facility 17 7.3 Technical Processes and Methods 17 7.3.1 Operational Flow 17 7.3.2 Methods 18 7.3.3 Data Reduction and Analysis 18 7.4 Verification of Technical Processes, Methods, and Software 18 7.4.1 Operational Flow Verification 18 7.4.2 Method Verifications 18 7.4.3 Data Reduction and Analysis Verification 18 7.5 Design of Quality Controls 18 7.5.1 General 19 7.5.2 Demonstration of Capability (D of C) 19 7.5.3 Process Control Checks 19 7.6 Counting Instrument Controls 20 8.0 PURCHASING AND SUBCONTRACT CONTROLS 21 8.1 General 21 8.2 Source Selection 21 8.3 Procurement of Supplies and Support Services 21 8.3.1 Catalog Supplies 21 8.3.2 Support Services 21 8.3.3 Equipment and Software 22 8.4 Subcontracting of Analytical Services 22 8.5 Acceptance of Items or Services 22 Page 3 of 32

TABLE OF CONTENTS - Continued 9.0 TEST SAMPLE IDENTIFICATION AND CONTROL 23 9.1 Sample Identification 23 9.2 LIMS 23 9.3 Sample Control 23 10.0 SPECIAL PROCESSES, INSPECTION, AND TEST 24 10.1 Special Processes 24 10.2 Inspections and Tests 24 10.2.1 Intra Laboratory Checks (QC Checks) 24 10.2.2 Inter Laboratory Checks 24 10.2.3 Data Reviews 24 10.3 Control of Sampling of Samples 24 10.4 Reference Standards / Material 24 10.4.1 Weights and Temperatures 25 10.4.2 Radioactive Materials 25 11.0 EQUIPMENT MAINTENANCE AND CALIBRATION 26 11.1 General 26 11.2 Support Equipment 26 11.3 Instruments 26 11.4 Nonconformances and Corrective Actions 26 11.5 Records 27 12.0 NONCONFORMANCE CONTROLS 28 12.1 General 28 12.2 Responsibility and Authority 28 12.3 10CFR21 Reporting 28 Page 4 of 32

TABLE OF CONTENTS - Continued 13.0 CORRECTIVE AND PREVENTIVE ACTIONS 29 13.1 General 29 13.2 Corrective Actions 29 13.3 Preventive Actions 29 14.0 RESULTS ANALYSIS AND REPORTING 30 14.1 General 30 14.2 Results Review 30 14.3 Reports 30 15.0 RECORDS 31 15.1 General 31 15.2 Type of Records 31 15.3 Storage and Retention 31 15.4 Destruction or Disposal 31 16.0 ASSESSMENTS 32 16.1 General 32 16.2 Audits 32 16.3 Management Reviews 32 Page 5 of 32

REVISION HISTORY Revision 7 Complete re-write January 1, 2005 Bill Meyer Revision 8 Updated organization chart, minor change to 1.0, 4.4, 7.5.3.2, 10.2.3, and 12.3 Page 6 of 32

1.0 Knoxville QAM Section Introduction This Quality Assurance Manual (QAM) and related Procedures describes the Knoxville Environmental Services Laboratorys QA system. This system is designed to meet multiple quality standards imposed by Customers and regulatory agencies including:

NRCs 10 CFR 50 Appendix B NRCs Regulatory Guide 4.15 DOEs Order 414.1 DOEs QSAS ANSI N 42.23 ANSI N 13.30 NELAC Standard, Chapter 5 The Environmental Services (ES) Laboratory does low level radioactivity analyses for Power Plants and other customers. It primarily analyzes environmental samples (natural products from around plants such as milk), in-plant samples (air filters, waters), bioassay samples from customers employees, and waste disposal samples (liquids and solids).

Potable and non-potable water samples are tested using methods based on EPA standards as cited in State licenses (see Procedure 4010). The listing [current as of initial printing of this Manual - see current index for revision status and additions / deletions] of implementing Procedures (SOPs) covering Administration, Methods, Counting Instruments, Technical, Miscellaneous, and LIMS is shown in Table 1-1. Reference to these Procedures by number is made throughout this QAM.

Table 1-1 Number Title Part 1 Administrative Procedures Validation and Verification of Computer Programs for Radiochemistry Data 1001 Reduction 1002 Organization and Responsibility 1003 Control, Retention, and Disposal of Quality Assurance Records 1004 Definitions 1005 Data Integrity 1006 Job Descriptions 1007 Training and Certifications 1008 Procedure and Document Control 1009 Calibration System 1010 Nonconformance Controls 1011 10CFR21 Reporting 1012 Corrective Action and Preventive Action Page 7 of 32

Number Title 1013 Internal Audits and Management Reviews 1014 RFP, Contract Review, and Order Entry (formerly 4001) 1015 Procurement Controls Part 2 Method Procedures 2001 Alpha Isotopic and Plutonium-241 2002 Carbon-14 Activity in Various Matrices Carbon-14 and Tritium in Soils, Solids, and Biological Samples; Harvey 2003 Oxidizer Method 2004 Cerium-141 and Cerium-144 by Radiochemical Separation 2005 Cesium-137 by Radiochemical Separation 2006 Iron-55 Activity in Various Matrices 2007 Gamma Emitting Radioisotope Analysis 2008 Gross Alpha and/or Gross Beta Activity in Various Matrices 2009 Gross Beta Minus Potassium-40 Activity in Urine and Fecal Samples 2010 Tritium and Carbon-14 Analysis by Liquid Scintillation 2011 Tritium Analysis in Drinking Water by Liquid Scintillation 2012 Radioiodine in Various Matrices 2013 Radionickel Activity in Various Matrices 2014 Phosphorus-32 Activity in Various Matrices 2015 Lead-210 Activity in Various Matrices 2016 Radium-226 Analysis in Various Matrices 2017 Total Radium in Water Samples 2018 Radiostrontium Analysis by Chemical Separation 2019 Radiostrontium Analysis by Ion Exchange 2020 Sulfur-35 Analysis 2021 Technetium-99 Analysis by Eichrom Resin Separation 2022 Total Uranium Analysis by KPA 2023 Compositing of Samples 2024 Dry Ashing of Environmental Samples 2025 Preparation and Standardization of Carrier Solutions 2026 Radioactive Reference Standard Solutions and Records 2027 Glassware Washing and Storage 2028 Moisture Content of Various Matrices 2029 Polonium-210 Activity in Various Matrices 2030 Promethium-147 Analysis Page 8 of 32

Number Title Part 3 Instrument Procedures 3001 Calibration and Control of Gamma-Ray Spectrometers 3002 Calibration of Alpha Spectrometers 3003 Calibration and Control of Alpha and Beta Counting Instruments 3004 Calibration and Control of Liquid Scintillation Counters 3005 Calibration and Operation of pH Meters 3006 Balance Calibration and Check 3008 Negative Results Evaluation Policy 3009 Use and Maintenance of Mechanical Pipettors 3010 Microwave Digestion System Use and Maintenance Part 4 Technical Procedures 4001 Not Used 4002 QC Checks on Data 4003 Sample Regent and Control 4004 Data Package Preparation and Reporting 4005 Blank, Spike, and Duplicate Controls 4006 Inter-Laboratory Comparison Study Process 4007 Method Basis and Initial Validation Process 4008 Not Used 4009 MDL Controls 4010 State Certification Process 4011 Accuracy, Precision, Efficiency, and Bias Controls and Data Quality Objectives 4012 Not Used 4013 Not Used 4014 Facility Operation and Control 4015 Documentation of Analytical Laboratory Logbooks (formerly 1002) 4016 Total Propagated Uncertainty (formerly 1004) 4017 LIMS Operation 4018 Instrument Calibration System 4019 Radioactive Reference Material Standards Part 5 Miscellaneous Procedures 5001 Laboratory Hood Operations 5002 Operation and Maintenance of Deionized Water System 5003 Waste Management 5004 Acid Neutralization and Purification System Operation Procedure Page 9 of 32

Part 6 LIMS 6001 LIMS Raw Data Processing and Reporting 6002 Software Development and/or Pilots of COTS Packages 6003 Software Change and Version Control 6004 Backup of Data and System Files 6005 Disaster Recovery Plan 6006 LIMS Hardware 6007 LIMS User Access 6008 LIMS Training 6009 LIMS Security 2.0 QUALITY SYSTEM The TBE-ES QA system is designed to comply with multiple customer- and regulatory agency-imposed specifications related to quality. This quality system applies to all activities of TBE-ES that affect the quality of analyses performed by the laboratory.

2.1 Policy The TBE quality policy, given in Company Policy P-501, is TBE will continually improve our processes and effectiveness in providing products and services that exceed our customers expectations.

This policy is amplified by this Laboratorys commitment, as attested to by the title page signatures, to perform all work to good professional practices and to deliver high quality services to our customers with full data integrity. (See Section 4.0 and Procedure 1005).

2.2 Quality System Structure The Quality System is operated by the organizations described in Section 3.0 of this Manual. The Quality System is described in this Manual and in the Procedures Manual, both of which are maintained by the QA Manager. Procedures are divided into 6 sections - Administrative, Methods, Equipments, Technical, Miscellaneous, and LIMS. This Manual is structured as shown in the Table of Contents and refers to Procedures when applicable. Cross references to the various imposed quality specifications are contained in Appendices to this Manual.

2.3 Quality System Objectives The Quality System is established to meet the objective of assuring all operations are planned and executed in accordance with system requirements. The Quality System also assures that performance evaluations are performed (see Procedure 4006), and that appropriate verifications are performed (see Procedures in the 1000 and 4000 series) to further assure compliance. Verification includes Page 10 of 32

examination of final reports (prior to submittal to customers) to determine their quality (see Procedure 4004).

To further these objectives, various in-process assessments of data, as well as assessments of the system, via internal audits and management reviews, are performed. Both internal experts and customer / regulatory agencies perform further assessments of the system and compliance to requirements.

2.4 Personnel Orientation, Training, and Qualification TBE provides indoctrination and training to employees and performs proficiency evaluation of technical personnel. This effort is described in Section 4.0.

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3.0 ORGANIZATION, AUTHORITY, AND RESPONSIBILITY TBE has established an effective organization for conducting laboratory analyses at the Knoxville Environmental Services Laboratory. The basic organization is shown in Figure 3-1. Detail organization charts with names, authorities, and responsibilities are given in Procedure 1002. Job descriptions are given in Procedure 1006.

This organization provides clearly established Quality Assurance authorities, duties, and functions. QA has the organizational freedom needed to:

(1) Identify problems (2) Stop nonconforming work (3) Initiate investigations (4) Recommend corrective and preventive actions (5) Provide solutions or recommend solutions (6) Verify implementation of actions All Laboratory personnel have the authority and resources to do their assigned duties and have the freedom to act on problems. The QA personnel have direct, independent access to Company management as shown in Figure 3-1.

President VP VP Administration & QA Environmental Product Assurance Director Lab QA Manager Lab Operations Manager Program Lab Administration Managers Supervisor Staff Figure 3.1. Laboratory Organization Page 12 of 32

4.0 PERSONNEL ORIENTATION, DATA INTEGRITY, TRAINING, AND QUALIFICATION 4.1 Orientation All laboratory personnel must receive orientation to the quality program if their work can affect quality. Orientation includes a brief review of customer- and regulatory agency-imposed quality requirements, the structure of the QAM, and the implementing procedures. The goal of orientation is to cover the nature and goals of the QA program.

4.2 Data Integrity The primary output of the Laboratory is data. Special emphasis and training in data integrity is given to all personnel whose work provides or supports data delivery. The Laboratory Data Integrity Procedure (Procedure 1005) describes training, personnel attestations, and monitoring operations. Annual reviews are required.

4.3 Training The Quality Assurance Manager (QAM) maintains a training matrix indicating which laboratory personnel need training in which specific Procedures. This matrix is updated when personnel change or change assignments. All personnel are trained per these requirements and procedures. This training program is described in Procedure 1007. The assigned responsibilities for employees are described in Procedure 1002 (See Section 3.0) on Organization and in Procedure 1006, Job Descriptions. Refresher training or re-training is given annually as appropriate.

4.4 Qualification Personnel are qualified as required by their job description. Management and non-analysts are evaluated based on past experience, education, and managements assessment of their capabilities. Formal qualification is required of analysts and related technical personnel who perform laboratory functions. Each applicable person is given training and then formally evaluated by the Operations Manager (or his designees) and by QA. Each analyst must initially demonstrate capability to perform each assigned analytical effort. Each year, thereafter, he or she must perform similar analyses on Interlab Comparison Samples (see Procedure 4006) or on equivalent blanks and spikes samples. Acceptable results extend qualifications (certification). Unacceptable results require retraining in the subject method / Procedures. (See Procedure 1007 for added information, records, forms, etc. used.)

4.5 Records Records of training subjects, contents, attendees, instructors, and certifications are maintained by QA.

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5.0 CUSTOMER INTERFACES 5.1 Interface Personnel The Laboratory has designated Program Managers as the primary interface with all customers. Other interfaces may be the QA Manager or the Lab Operations Manager.

5.2 Bid Requests and Tenders The Program Managers respond to customer requests for bids and proposals per Procedure 1014 for bids, proposals, and contract reviews. They clarify customer requests so both the customer and the lab staff understand requests. As responses are developed, internal reviews are conducted to ensure that requirements are adequately defined and documented and to verify that the Laboratory has adequate resources in physical capabilities, personal skills, and technical information to perform the work. Accreditation needs are reviewed. If subcontracts are required to perform any analysis, the subcontractor is similarly evaluated and the client notified in writing of the effort. Most qualifications are routine with standard pricing and the review of these quotes is performed by the Program Manager. Larger or more complex quotes are reviewed by the Operations Manager and the QA Manager (or designees). Evidence of review is by initialing and dating applicable papers, signatures on quotations, or by memo.

5.3 Contracts The Program Managers receive contract awards (oral or written) and generate the work planning for initiation preparation (charge numbers, data structure or contents in LIMS, etc.). They review contracts for possible differences from quotations and, if acceptable, contracts are processed. Documentation of the review is by initials and date as a minimum. Contract changes receive similar reviews and planning.

5.4 TBEs Expectation of Customers TBE expects customers to provide samples suitable for lab analysis. These expectations include:

Accurate and unambiguous identification of samples Proper collection and preservation of samples Use of appropriate containers free from external and internal contamination Integrity preservation during shipment and timely delivery of samples that are age sensitive Adequate sized samples that allow for retest, if needed Specification of unique MOA/MDC requirements Alerting the lab about abnormal samples (high activity, different chemical contents, etc.)

Chain of custody initiation, when required.

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5.5 Customer Satisfaction TBEs quality policy centers on customer satisfaction (See 2.0). TBE will work to satisfy customers through full compliance with contract requirements, providing accurate data and properly responding to any questions or complaints.

Customers are provided full cooperation in their monitoring of Laboratory performance. Customers are notified if any applicable State Accreditation is withdrawn, revoked, or suspended.

5.5.1 Customer Complaints Any customer complaints are documented and tracked to closure. Most complaints concern analysis data and are received by Program Managers. They log each such complaint, order retests for verification, and provide documented results to customers. Complaints may also be received by QA or Operations.

If complaints are other than re-test type, the nonconformance and corrective action systems (Sections 12 and 13) are used to resolve them and record all actions taken.

5.5.2 Customer Confidentiality All laboratory personnel maintain confidentiality of customer-unique information.

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6.0 DOCUMENTATION GENERATION & CONTROL 6.1 General The documentation generation and control system is detailed in Procedure 1008. An overview is given below. The basic quality system documents are described in Section 2.0.

6.2 New Documentation Each Procedure and this QAM is written by appropriate personnel, validated if applicable (see Section 7.0), reviewed for adequacy, completeness, and correctness, and, if acceptable, accepted by the authorized approver [QA Manager, Operations Manager (or their designee)]. Both approvals are required if a Procedure affects both QA and Operations. (See Responsibilities in Section 3.0). These procedures control the quality measurements and their accuracy.

Each document carries a unique identification number, a revision level, dates, page numbers and total page count, and approver identification and sign off. If TBE writes code for software, the software is version identified and issued after Verification and Validation per Section 7.0.

6.3 Documentation Changes Each change is reviewed in the same manner and by the same people as new documentation. Revision identifications are updated and changes indicated by side bars, italicized words, or by revision description when practical. Obsolete revisions are maintained by QA after being identified as obsolete.

6.4 Documentation Lists and Distributions Computer indexes of documents are maintained by Quality showing the current authorized revision level of each document. These revisions are placed on the Laboratory server and obsolete ones are removed so that all personnel have only the current documents. If hard copies are produced and distributed, separate distribution lists are maintained indicating who has them and their revision level(s).

Copies downloaded off the server are uncontrolled unless verified by the user (on the computer) to be the latest revision.

6.5 Other Documentation In addition to TBE-generated documentation, QA maintains copies of applicable specifications, regulations, and standard methods.

6.6 Documentation Reviews Each issued document is reviewed at least every third year by the approving personnel. This review determines continued suitability for use and compliance with requirements.

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7.0 DESIGN OF LABORATORY CONTROLS 7.1 General The Laboratory and its operating procedures are designed specifically for low level (environmental and in-plant) radioactive sample analysis. The various aspects of the laboratory design include the following which are discussed in subsequent paragraphs of this Section:

(a) Facility (b) Technical Processes and Methods (c) Verification of Design of Processes, Methods, and Software.

(d) Design of Quality Controls (e) Counting Instrument Controls 7.2 Facility The facility was designed and built in 2000 to facilitate correct performance of operations in accordance with good laboratory practices and regulatory requirements. It provides security for operations and samples. It separates sample storage areas based on activity levels, separates wet chemistry from counting instrumentation for contamination control, and provides space and electronic systems for documentation, analysis, and record storage. Procedure 4014 describes the facility, room uses, layouts, etc.

7.3 Technical Processes and Methods 7.3.1 Operational Flow The laboratory design provides for sample receipt and storage (including special environmental provisions for perishable items) where samples are received from clients and other labs (see Section 9.0). The samples are logged into the computer based Laboratory Information Management System (LIMS) and receive unique identification numbers and bar code labels. (See Procedure 4017 for LIMS description and user procedures). The Program Managers then plan the work and assure LIMS contains any special instructions to analysts. Samples then go to sample preparation, wet chemistry (for chemical separation), and counting based on the radionuclides. See Procedures in the 2000 and 3000 series. Analysts perform the required tasks with data being entered into logbooks, LIMS, and counting equipment data systems as appropriate. Results are collected and reviewed by the Operations Manager and Program Managers and reports to clients are generated (See Section 14.0). All records (electronic or hard copy) are maintained in files or in back-up electronic copies (see Section 15.0). After the required hold periods and client notification and approval, samples are disposed of in compliance with regulatory requirements (see Procedures 5003 and 5004).

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7.3.2 Methods The laboratory methods documented in the 2000 and 3000 series of Procedures were primarily developed by senior TBE laboratory personnel based on years of experience at our prior facility in New Jersey. They have been improved, supplemented and implemented here. Where EPA or other accepted national methods exist (primarily for water analyses under State certification programs - see Procedure 4010), the TBE methods conform to the imposed requirements or State accepted alternate requirements. Any method modifications are documented and described in the Procedure. There are no nationally recognized methods for most other analysis methods but references to other method documents are noted where applicable.

7.3.3 Data Reduction and Analysis Whenever possible automatic data capture and computerized data reduction programs are used. Calculations are either performed using commercial software (counting system operating systems) or TBE developed and validated software is used (see 7.4 below). Analysis of reduced data is performed as described in Section 14.0 and Procedure 4004.

7.4 Verification of Technical Processes, Methods, and Software 7.4.1 Operational Flow Verification The entire QA Manual and related procedures describe the verification of elements of the technical process flow and the establishment of quality check points, reviews, and controls.

7.4.2 Method Verifications Methods are verified and validated per Procedure 4007 prior to use unless otherwise agreed to by the client. For most TBE methods initial validation occurred well in the past. New or significantly revised Methods receive initial validation by demonstration of their performance using known analytes (NIST traceable) in appropriate matrices. Sufficient samples are run to obtain statistical data that provides evidence of process capability and control, establishes detection levels (see procedure 4009), bias and precision data (see Procedure 4011). All method procedures and validation data are available to respective clients. Also see Section 7.5 below for the Demonstration of Capability program.

7.4.3 Data Reduction and Analysis Verification Data reduction and analysis verification is performed by personnel who did not generate the data. (See Section 14.0).

7.5 Design of Quality Controls Page 18 of 32

7.5.1 General There are multiple quality controls designed into the laboratory operations.

Many of these are described elsewhere in this manual and include personnel qualification (Section 4.0), Document control (6.0), Sample identification and control (9.0), Use of reference standards (10.0), intra- and inter- laboratory tests (10.0), etc.

This Section describes the basic quality control systems used to verify Method capability and performance.

7.5.2 Demonstration of Capability (D of C)

The demonstration of capability system verifies and documents that the method, analyst, and the equipment can perform within acceptable limits. The D of C is certified for each combination of analyte, method, and instrument type. D of C's are certified based on objective evidence at least annually. This program is combined with the analyst D of C program (See Section 4.0). Initial D of C's use the method validation effort as covered above. Subsequent D of C's use Inter-Laboratory samples (Procedure 4006) or, if necessary, laboratory generated samples using NIST traceable standards. If results are outside of control limits, re-demonstration is required after investigation and corrective action is accomplished (See Sections 12.0 and 13.0) 7.5.3 Process Control Checks Process control checks are designed to include Inter-Lab samples, Intra-lab QC check samples, and customer provided check samples. 10% of laboratory analysis samples are for process control purposes.

7.5.3.1 Inter- Lab Samples. Inter-lab samples are procured or obtained from sources providing analytes of interest in matrices similar to normal client samples. These samples may be used for Demonstration of Capability of analyst's, equipment and methods. They also provide for independent insight into the lab's process capabilities. Any value reported as being in the warning zone (over 2 sigma) is reviewed and improvements taken. Any value failing (over 3 sigma) is documented on an NCR and formal investigation per Section 12.0 and 13.0 is performed. If root causes are not clearly understood and fixed, re-tests are required using lab prepared samples (See Procedure 4006).

7.5.3.2 QC Samples. QC samples, along with Inter-lab samples and customer check samples, are 10% of the annual lab workload for the applicable analyte and method. If batch processing is used, some specifications require specific checks with each batch or each day rather than as continuous process controls.

(See Procedure 4005)

QC samples consist of multiple types of samples including:

(a) Method blanks (b) Blank spikes (c) Matrix spikes Page 19 of 32

(d) Duplicates (e) Tracers and carriers Acceptance limits for these samples are given in Procedures or in lab standards. The number, frequency, and use of these sample types varies with the method, matrix, and supplemental requirements. The patterns of use versus method and the use of the resulting test data is described in Procedure 4005.

7.5.3.3 Customer Provided Check Samples. Customers may provide blind check samples and duplicates to aid in their evaluation of the Laboratory. When the lab is notified that samples are check samples their results are included in the QC sample percentage counts. Any reported problems are treated as formal complaints and investigated per Section 5.

7.6 Counting Instrument Controls The calibration of instruments is their primary control and is described in Section 11.0. In addition, counting procedures (3000 series) also specify use of background checks (method blank data is not used for this) to evaluate possible counting equipment contamination. Instrument calibration checks using a lab standard from a different source than the one used for calibration are also used.

Background data can be used to adjust client and test data. Checks with lab standards indicate potential calibration changes.

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8.0 PURCHASING AND SUBCONTRACT CONTROLS 8.1 General Procurement and Subcontracts efforts use the Huntsville-based Cost Point computer system to process orders. The Laboratory-generated Purchase Requisitions are electronically copied into Purchase Orders in Huntsville. The Laboratory also specifies sources to be used. Procured items and services are received at the Laboratory where receiving checks and inspections are made.

Laboratory Procedure 1015 provides details on the procurement control system at the Laboratory and references the Huntsville procedures as applicable.

8.2 Source Selection Sources for procurements of items and services are evaluated and approved by QA as described in Procedure 1015. Nationally recognized catalog item sources are approved by the QA Manager based on reputation. Maintenance services by an approved distributor or the equipment manufacturing company are pre-approved.

Sources for other services are evaluated by QA, based on service criticality to the quality system, by phone, mail out, or site visit.

Subcontract sources for laboratory analysis services are only placed with accredited laboratories (by NELAP, NUPIC, State, Client, etc.) as applicable for the type of analysis to be performed. QA maintains lists of approved vendors and records of evaluations performed.

8.3 Procurement of Supplies and Support Services 8.3.1 Catalog Supplies The Laboratory procures reagents, processing chemicals, laboratory glassware, consumables, and other catalog items from nationally known vendors and to applicable laboratory grades, purities, concentrations, accuracy levels, etc.

Purchase Requisitions for these items specify catalog numbers or similar call-outs for these off-the-shelf items. Requisitions are generated by the personnel in the lab needing the item and are approved by the Operations or Production Manager.

Reagents are analytical reagent grade only.

8.3.2 Support Services Purchase Requisitions for support services (such as balance calibration, equipment maintenance, etc.) are processed as in 8.3.1 but technical requirements are specified and reviewed before approvals are given.

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8.3.3 Equipment and Software Purchase Requisitions for new equipment, software programs, and major facility modifications affecting the quality system are reviewed and approved by the Operations Manager and the QA Manager.

8.4 Subcontracting of Analytical Services When necessary, the Laboratory may subcontract analytical services required by a client. This may be because of special needs, infrequency of analysis, etc.

Applicable quality and regulatory requirements are imposed in the Purchase Requisition and undergo a technical review by QA. TBE reserves the right of access by TBE and our client for verification purposes.

8.5 Acceptance of Items or Services Items and services affecting the quality system are verified at receipt based on objective evidence supplied by the vendor. Supply items are reviewed by the requisitioner and, if acceptable, are accepted via annotation on the vendor packing list or similar document. Similarly, equipment services are accepted by the requisitioning lab person. Calibration services are accepted by QA based on certification reviews. (See Section 11.0.)

Data reports from analytical subcontractors are evaluated by Program Managers and subsequently by the Operations Manager (or designee) as part of client report reviews.

Items are not used until accepted and if items or services are rejected, QA is notified and nonconformance controls per Section 12.0 are followed. Vendors may be removed from the approved vendors list if their performance is unacceptable.

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9.0 TEST SAMPLE IDENTIFICATION AND CONTROL 9.1 Sample Identification Incoming samples are inspected for customer identification, container condition, chain of custody forms, and radioactivity levels. If acceptable, the sample information is entered into LIMS which generates bar coded labels for attachment to the sample(s). The labels are attached and samples stored in the assigned location.

If environmental controls are needed (refrigeration, freezing, etc.), the samples are placed in these storage locations. If not acceptable, the Program Manager is notified, the customer contacted, and the problem resolved (return of sample, added data receipts, etc.). See Procedure 4003 for more information on sample receipt.

9.2 LIMS The LIMS is used to schedule work, provide special information to analysts, and record all actions taken on samples. See Procedure 4017 and the 6000 series of procedures for more information on LIMS operations.

9.3 Sample Control The sample, with its bar coded label, is logged out to the applicable lab operation where the sample is processed per the applicable methods (Procedures 2000 and 3000). The LIMS-assigned numbers are used for identification through all operations to record data. Data is entered into LIMS, log books (kept by the analysts) or equipment data systems to record data. The combination of LIMS, logbooks, and equipment data systems provide the Chain of Custody data and document all actions taken on samples. Unused sample portions are returned to its storage area for possible verification use. Samples are discarded after required time limits are passed and after client notification and approval, if required.

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10.0 SPECIAL PROCESSES, INSPECTION, AND TEST 10.1 Special Processes The Laboratorys special processes are the methods used to analyze a sample and control equipment. These methods are defined in Procedures in the 2000 and 3000 series. These processes are performed to the qualified methods (see Section 7.0) by qualified people (see 4.0).

10.2 Inspections and Tests The quality of the process is monitored by indirect means. This program involves calibration checks on counting equipments (see Section 11.0), intra-laboratory checks, and inter-laboratory checks. In addition, some customers submit quality control check samples (blinds, duplicates, external reference standards). All generated data gets independent reviews.

10.2.1 Intra Laboratory Checks (QC Checks)

The quantity and types of checks varies with the method, but basic checks which may include blanks, spiked blanks, matrix spikes, matrix spike duplicates, and duplicates are used as appropriate for customer samples. This process is described in Procedure 4005 and in Section 7.0.

10.2.2 Inter Laboratory Checks TBE participates in Inter-lab performance evaluation (check) programs with multiple higher level labs. These programs provide blind matrices for the types of matrix/analyte combinations routinely processed by the Lab, if available. This program is described in Procedure 4006.

10.2.3 Data Reviews Raw data and reports are reviewed by the Operations Manager, or designees. This review checks for data logic, expected results, procedure compliance, etc. (See Section 14.0).

10.3 Control of Sampling of Samples Samples for analysis are supplied by customers preferably in quantities sufficient to allow re-verification analyses if needed. The samples are prepared for analysis by analysts and then an aliquot (partial sample extraction) is taken from the homogeneous customer sample for the initial analysis. Methods specify standard volumes of sample material required. Sampling data is recorded in LIMS and/or logbooks.

10.4 Reference Standards / Material Page 24 of 32

10.4.1 Weights and Temperatures Reference standards are used by the Laboratorys calibration vendor to calibrate the Labs working instruments measuring weights and thermometers.

10.4.2 Radioactive Materials Reference radioactive standards, traceable to NIST, are procured from higher level laboratories. These reference materials are maintained in the standards area and are diluted down for use by laboratory analysts. All original and diluted volumes are fully traceable to source, procedure, analyst, dilution, and acquisition dates. See Section 11.0 and Procedure 1009.

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11.0 EQUIPMENT MAINTENANCE AND CALIBRATION 11.1 General There are two types of equipment used by the Laboratory: support equipment (scales, glassware, weights, thermometers, etc.) and instruments for counting. Standards traceable to NIST are used for calibration and are of the needed accuracy for laboratory operations. Procedures 1009, 4018, and 4019 describe the calibration and maintenance programs.

11.2 Support Equipment Analytical support equipment is purchased with the necessary accuracies and appropriate calibration data. If needed, initial calibration by the Laboratory or its calibration vendor is performed. Recalibration schedules are established and equipment recalibrated by the scheduled date by a calibration vendor or by Laboratory personnel. Maintenance is performed, as needed, per manufacturers manuals or lab procedures.

In addition to calibrations and recalibrations, checks are made on the continued accuracy of items as described in Procedure 1009. Records are maintained of calibration and specified checks.

11.3 Instruments Instruments receive initial calibration using radioactive sources traceable to NIST. The initial calibration establishes statistical limits of variation that are used to set control limits for future checks and recalibration. This process is described in Procedure 4018. Instruments are maintained per Instrument Manual requirements.

Recalibrations are performed per the Procedure.

Between calibrations, check sources are used to assure no significant changes have occurred in the calibration of items. Background checks are performed to check for possible radioactive contamination. Background values are used to adjust sample results. Hardware and software are safeguarded from adjustments that could invalidate calibrations or results.

11.4 Nonconformances and Corrective Actions If calibrations or checks indicate a problem, the nonconformance system (Section 12.0) and corrective action system (Section 13.0) are initiated to document the problem and its resolution. Equipment is promptly removed from service if questionable.

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11.5 Records Records of calibrations are maintained. Calibration certificates from calibration vendors are maintained by QA. Other calibration data and check data is maintained in log books, LIMS, or instrument software as appropriate and as described in Procedures 1009, 4018, and 4019.

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12.0 NONCONFORMANCE CONTROLS 12.1 General The nonconformance control system is implemented whenever a nonconforming condition on any aspect of Laboratory analysis, testing, or results exist. The system takes graded actions based on the nature and severity of the nonconformance. Nonconforming items or processes are controlled to prevent inadvertent use. Nonconformances are documented and dispositioned. Notification is made to affected organizations, including clients. Procedure 1010 describes the procedures followed. Sample results are only reported after resolution.

12.2 Responsibility and Authority Each Laboratory employee has the responsibility to report nonconformances and the authority to stop performing nonconforming work or using nonconforming equipment. Laboratory supervision can disposition and take corrective actions on minor problems. Any significant problem is documented by QA using the Laboratorys NCR system per Procedure 1010. QA conducts or assures the conduct of cause analyses, disposition of items or data, and initiation of corrective action if the nonconformance could recur.

12.3 10CFR21 Reporting The QA Manager reviews NCRs for possible need of customer and/or NRC notification per the requirements of 10CFR21. Procedure 1011 is followed in this review and for any required reporting.

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13.0 CORRECTIVE AND PREVENTIVE ACTIONS 13.1 General The Laboratory takes corrective actions on significant nonconformances (see Section 12.0). It also initiates preventive and improvement actions per the Company Quality Policy (see Section 2.0). The procedures for Corrective Action/Preventive Action systems are contained in Procedure 1012.

13.2 Corrective Actions Corrective actions are taken by Operations and Quality to promptly correct significant conditions adverse to quality. The condition is identified and cause analysis is performed to identify root causes. Solutions are evaluated and the optimum one selected that will prevent recurrence, can be implemented by the Laboratory, allows the Laboratory to meet its other goals, and is commensurate with the significance of the problem. All steps are documented, action plans developed for major efforts, and reports made to Management. QA verifies the implementation effectiveness. Procedure 1012 provides instructions and designates authorities and responsibilities.

13.3 Preventive Actions Preventive actions are improvements intended to reduce the potential for nonconformances. Possible preventive actions are developed from suggestions from employees and from analysis of Laboratory technical and quality systems by management. If preventive actions or improvements are selected for investigation, the issues, investigation, recommendations, and implementation actions are documented. Follow up verifies effectiveness.

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14.0 RESULTS ANALYSIS AND REPORTING 14.1 General The Laboratorys role is to provide measurement-based information to clients that is technically valid, legally defensible, and of known quality.

14.2 Results Review The results obtained from analytical efforts are collected and reviewed by the Operations Manager and the Program Manager. This review verifies the reasonableness and consistency of the results. It includes review of sample and the related QC activity data. Procedure 4002 describes the process. Any deficiencies are corrected by re-analyses, recalculations, or corrective actions per Sections 12.0 and 13.0. Use of the LIMS with its automatic data loading features (see Procedure 4017) minimizes the possibility of transcription or calculation errors.

14.3 Reports Reports range from simple results reporting to elaborate analytical reports based on the client requirements and imposed specifications and standards. (See Procedure 4004.) Reports present results accurately, clearly, unambiguously, objectively, and as required by the applicable Method(s). Reports include reproduction restrictions, information on any deviations from methods, and any needed data qualifiers based on QC data. If any data is supplied by analytical subcontractors (see Section 8.0), it is clearly identified and attributed to that Laboratory by either name or accreditation number.

If results are faxed or transmitted electronically, confidentiality statements are included in case of receipt by other than the intended client.

Reports are approved by the Program Manager and Operations Manager and record copies kept in file (See Section 15.0).

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15.0 RECORDS 15.1 General The Laboratory collects generated data and information related to quality or technical data and maintains them as records. Records are identified, prepared, reviewed, placed in storage, and maintained as set forth in Procedure 1003.

15.2 Type of Records All original observations, calculations, derived data, calibration data, and test reports are included. In addition QA data such as audits, management reviews, corrective and preventive actions, manuals, and procedures are included.

15.3 Storage and Retention Records are stored in files after completion in the lab. Files are in specified locations and under the control of custodians. Filing systems provide for retrieval.

Electronic files are kept on Company servers (with regular back up) or on media stored in fireproof file cabinets. Records are kept in Laboratory files for at least 2 years after the last entry and then in Company files for another year as a minimum.

Some customers specify larger periods - up to 7 years - which is also met. Generic records supporting multiple customers are kept for the longest applicable period.

15.4 Destruction or Disposal Records may be destroyed after the retention period and after client notification and acceptance, if required. If the Laboratory closes, records will go in to company storage in Huntsville unless otherwise directed by customers. If the Laboratory is sold, either the new owner will accept record ownership or the records will go into Company storage as stated above.

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16.0 ASSESSMENTS 16.1 General Assessments consist of internal audits and management reviews as set forth in Procedure 1013.

16.2 Audits Internal audits are planned, performed at least annually on all areas of the quality system, and are performed by qualified people who are as independent as possible from the activity audited. (The Laboratorys small size inhibits full independence in some technical areas.) Audits are coordinated by the Quality Manager who assures audit plans and checklists are generated and the results documented. Reports include descriptions of any findings and provide the auditors assessment of the effectiveness of the audited activity. Report data includes personnel contacted.

Audit findings are reviewed with management and corrective actions agreed to and scheduled. Follow up is performed by QA to verify accomplishment and effectiveness of the corrective action.

16.3 Management Reviews The Annual Quality Assurance Report, prepared for some clients, is the Management Review vehicle. These reports cover audit results, corrective and preventive actions, external assessments, and QC and inter-laboratory performance checks. The report is reviewed with Management by the QA Manager for the continued suitability of the Quality Program and its effectiveness. Any needed improvements are defined, documented, and implemented. Follow ups are made to verify implementation and effectiveness.

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Revision 0 APPENDIX D LABORATORY ANALYTICAL REPORTS D.1 ENVIRONMENTAL, INC.

D.2 TELEDYNE BROWN ENGINEERING, INC.

045136 (13) Byron Generating Station

Revision 0 D.1 ENVIRONMENTAL, INC.

045136 (13) Byron Generating Station

Revision 0 D.2 TELEDYNE BROWN ENGINEERING, INC.

045136 (13) Byron Generating Station

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