ML14030A287

Plan Completion Report for the VB 6 Area

ML14030A287
Person / Time
Site:	Braidwood
Issue date:	08/31/2009
From:	Conestoga-Rovers & Associates
To:	Exelon Generation Co, Office of Nuclear Reactor Regulation
Shared Package
ML14030A308	List: ML14030A264 ML14030A266 ML14030A267 ML14030A268 ML14030A269 ML14030A273 ML14030A274 ML14030A275 ML14030A276 ML14030A278 ML14030A279 ML14030A280 ML14030A284 ML14030A285 ML14030A286 ML14030A287 ML14030A288 ML14030A289 ML14030A290 ML14030A291 ML14030A292 ML14030A293 ML14030A294 ML14030A295 RS-14-029, Annual Report on the Meteorological Monitoring Program at the Braidwood Nuclear Power Station 2008 RS-14-029, Annual Report on the Meteorological Monitoring Program at the Braidwood Nuclear Power Station 2009 RS-14-029, Annual Report on the Meteorological Monitoring Program at the Braidwood Nuclear Power Station 2011 RS-14-029, Annual Report on the Meteorological Monitoring Program at the Braidwood Nuclear Power Station 2012 RS-14-029, Braidwood Station Kankakee River Fish Monitoring Program, 1991-2013 - Tables Requested by the NRC to Describe the Number of Fish Caught by Sampling Gear and Species at Each Monitoring Location RS-14-029, Braidwood Station Kankakee River Fish Monitoring Program, 2010 RS-14-029, Braidwood Station, 2011 Benthos Monitoring and Historical Fish and Benthos Comparisons RS-14-029, Braidwood Station, Kankakee River Fish Monitoring Program, 2012 RS-14-029, Employment and Land Requirements for Alternatives to Byron Units 1 and 2 and Braidwood Units 1 and 2 - Lr Chapter 7 Energy Alternatives RS-14-029, Final Report: Characterization of Unionid Communities Near the Braidwood Nuclear Station Kankakee River Discharge Location RS-14-029, Final Report: Unionid Relocation Near the Braidwood Nuclear Station Kankakee River Discharge Location RS-14-029, Investigations to Determine Presence of State-Listed Species of Fish and Freshwater Mussels in the Kankakee River Near the Braidwood Nuclear Station Warmwater Discharge Channel RS-14-029, Monthly Report on the Meteorological Monitoring Program at the Braidwood Nuclear Generating Station RS-14-029, Plan Completion Report for the VB 1 Area RS-14-029, Plan Completion Report for the VB 2/3 and Pond Area RS-14-029, Plan Completion Report for the VB 4 Area RS-14-029, Plan Completion Report for the VB 6 Area RS-14-029, Plan Completion Report for the VB 7 Area RS-14-029, Standard Operating Procedures for Braidwood Station'S Fisheries Monitoring Program in the Kankakee River and Horse Creek RS-14-029, Status of Fish Communities and Sport Fishery in the Kankakee River and Tributary Streams: 2005 Basin Survey RS-14-029, Transmittal of Annual Report on the Meteorological Monitoring Program at the Braidwood Nuclear Power Station 2010 RS-14-029, Transmittal of Application for an Incidental Take Permit for Threatened or Endangered Species and Conservation Plan
References
RS-14-029 046907 (7)
Download: ML14030A287 (28)

Text

.4 PLAN COMPLETION REPORT FOR THE VB 6 AREA BRAIDWOOD GENERATION STATION BRACEVILLE, ILLINOIS Prepared For: Exelon Generation Company, LLC DISCLAIMER:

SOME FORMATTING CHANGES MAY HAVE OCCURRED WHEN THE ORIGINAL DOCUMENT WAS PRINTED TO PDF; HOWEVER, THE ORIGINAL CONTENT REMAINS UNCHANGED.

Prepared by: Conestoga-Rovers

& Associates 8615 West Bryn Mawr Chicago, Illinois 60631 AUGUST 2009 REF. NO. 046907 (7)This report is printed on recycled paper.Office: (773) 380-9933 Fax: (773) 380-6421 web: http:\\www.CRAwodd.com b.TABLE OF CONTENTS Page

1.0 INTRODUCTION

...............................................................................................................

1

1.1 BACKGROUND

AND PURPOSE ................................................................

1

1.2 DESCRIPTION

OF THE REMEDIATION AREA .....................................

2 1.3

SUMMARY

OF REMEDIAL ACTIONS TO DATE AND CURRENT GROUNDWATER CONDITIONS

.............

2 2.0 CURRENT GROUNDWATER CONDITIONS AT VB 6 ..............................................

3

2.1 BACKGROUND

.............................................................................................

3 2.2 PRE-REMEDIATION GROUNDWATER CONDITIONS

........................

3 2.3 REMEDIAL ACTION PLAN IMPLEMENTED AT VB 6 .........................

4 2.4 CURRENT GROUNDWATER CONDITIONS

.........................................

4 2.5 EVALUATION OF REMEDIAL ACTIVITIES TO DATE ........................

5

3.0 CONCLUSION

S

......................................................................................................................

7 4.0 PLANNED COMPLETION ACTIVITIES

........................................................................

8

5.0 REFERENCES

..........................................................................................................................

9 046907(7)

CONESTOGA-ROVERS

& AssociATEs 046907 (7)CONEsToGA-ROVERS

& AssoctATEs LIST OF FIGURES (Following Text)FIGURE 1.1 FIGURE 1.2 FIGURE 2.1 FIGURE 2.2 FIGURE 2.3 FIGURE 2.4 FIGURE 2.5 FIGURE 2.6 FIGURE 2.7 FIGURE 2.8 SITE LOCATION MAP LOCATION MAP FOR VB 6 AREA MONITORING WELL LOCATIONS

-VB 6 GROUNDWATER LEVEL CONTOURS -MARCH 2006 -SHALLOW GROUNDWATER ZONE GROUNDWATER LEVEL CONTOURS -MARCH 2006 -DEEP GROUNDWATER ZONE ESTIMATED TRITIUM RESULTS -MARCH 2006 -SHALLOW GROUNDWATER ZONE ESTIMATED TRITIUM RESULTS -MARCH 2006 -DEEP GROUNDWATER ZONE TRITIUM CONCENTRATION TRENDS AROUND VB 6 AREA GROUNDWATER LEVEL CONTOURS -VB 6 AND VB 7 AREAS -SEPTEMBER 15-18, 2008 ESTIMATED TRITIUM RESULTS -SEPTEMBER 2008 -VB 6 GROUNDWATER ZONE 048907 (7) CONESTOGA-ROVERS

& ASSOCIATES 046907 (7)CONESTOGA-ROVERS

& AssocIATES "I LIST OF TABLES (Following Text)TABLE 2.1 TABLE 4.1

SUMMARY

OF TRITIUM STATISTICAL ANALYSES NEAR VB 6

SUMMARY

OF WELLS TO BE ABANDONED 048907(7)

CONESTOGA-ROVERS

& Assoc~Es 046907 (7)CONEsToGA-RovERs

& AssoctATEs 4

1.1 BACKGROUND

AND PURPOSE This document has been prepared for the Illinois Environmental Protection Agency (IEPA) to address on-going groundwater remediation at the Exelon Generation Company LLC (Exelon) Braidwood Generating Station property' located in Braceville, Illinois.

More specifically, this Plan Completion Report addresses the Vacuum Breaker#6 area (Site) and discusses the groundwater investigation, monitoring, and remedial actions that were implemented in accordance with the Agreed Preliminary Injunction Order (PIO) dated May 24, 2006. Information collected to date as a result of Action Plan implementation is sufficient to determine that remediation at the VB 6 area is complete and can be concluded.

Among other things, the May 24, 2006 PIO required Exelon to submit a Groundwater Action Plan to address tritium in groundwater at or near Braidwood Generating Station's Vacuum Breaker #6 (VB 6). In November 2006, the Minimization Impairment Plan for Vacuum Breaker 6 was prepared and submitted to the IEPA (hereinafter referred to as the "Action Plan"). Upon approval by the IEPA, the Action Plan was implemented.

As a result of the implementation of the approved Action Plan, the levels of tritium detected in groundwater have been reduced to below the Lower Level of Detection (LLD) of 200 picocuries per liter (pCi/L) in the VB 6 area. Additionally, a significant amount of environmental data has been collected as part of the Action Plan implementation.

Analyses of these data have revealed the geologic and hydrogeologic characteristics of the subject area, providing an understanding of the groundwater movement and tritium migration.

This Plan Completion Report for the VB 6 area is based on Site characterization data collected through May 2009 which indicate a substantial reduction in tritium levels through passive remediation.

Information collected to date as a result of Action Plan implementation is sufficient to determine that remediation at the VB 6 area is complete and can be concluded.

Section 5.0 of this Plan Completion Report provides a list of references specific to the VB 6 area as well as pertinent documents related to the other areas on the Braidwood Station property where remediation of tritium in groundwater is being performed.

1 The Braidwood Station property includes lands listed under the Station's Nuclear Regulatory Commission (NRC) licensed property along the blowdown line and property recently purchased by Exelon along Smiley Road and Center Street.046907 (7)1 CONEsToGA-ROVERS

& AssociATEs

1.2 DESCRIPTION

OF THE REMEDIATION AREA Land surrounding the VB 6 area falls mainly into the agricultural, residential, and recreational use categories (Figure 1.1). The center of the Village of Braidwood is approximately 10,000 feet from the vacuum breaker VB 6. To the northwest of the Site, there are two main highways (Illinois State Highway 53 and Illinois Route 129) running parallel to each other with a railroad (Southern Pacific Railroad) between them. The Will County Forest Preserve is located to the north of the Site. Five monitoring wells have been installed in the vicinity of the Site (Figure 1.2).1.3

SUMMARY

OF REMEDIAL ACTIONS TO DATE AND CURRENT GROUNDWATER CONDITIONS The current groundwater remediation program for the VB 6 area utilizes passive techniques, which includes monitored natural attenuation (MNA).The concentration of tritium in groundwater at monitoring wells in the VB 6 area has been reduced by as much as 100% since September 2006 (e.g., MW-148D and MW-150D).As of May 2009, tritium concentrations in groundwater samples collected from all the monitoring wells at the VB 6 location were below the LLD of 200 pCi/L. All monitoring wells at the VB 6 location have been below the LLD for six consecutive sampling events since December 2007.046907(7) 2 CONESTOGA-ROVERS

& AssociATEs 046No7 (7)2 CONEsToGA-RovERs

& AssoctATEs

2.0 CURRENT

GROUNDWATER CONDITIONS AT VB 6 This section presents a description of the pre-remediation and current groundwater conditions at the VB 6 area.

2.1 BACKGROUND

Vacuum breaker VB 6 is located on the blowdown line about 425 yards east of Essex Road and 450 yards north of Smiley Road on the Exelon transmission tower right-of-way (Figure 1.2). This land is leased to a local resident for agriculture.

The Will County Forrest Preserve District (WCFPD) owns the property directly north of the right-of-way.

A search of work history for leaks from the VB 6 and its associated air release valve determined the following:

• Engineers discovered minor leakage of the main seat on November 10, 2000. The valve had been previously verified leak free on March 3, 2000.* Another main seat leak with the same description was discovered on October 30, 2003. This leak was repaired on October 17, 2005.2.2 PRE-REMEDIATION GROUNDWATER CONDITIONS A total of 20 monitoring wells have been installed into the deep and shallow zones of the overburden sand aquifer in the VB 6 area. The majority of these monitoring wells have been abandoned.

Currently, there are five monitoring wells in the VB 6 area used for routine groundwater monitoring.

Figure 2.1 presents the monitoring well network in the vicinity of VB 6. This figure includes temporary 1-inch diameter monitoring wells and permanent 2-inch diameter monitoring wells.Figures 2.2 and 2.3 present the groundwater elevations and flow directions in the shallow and deep zones of the overburden sand aquifer for March 2006, respectively.

Groundwater in the vicinity of VB 6 flows generally northeast in the deep zone.Figures 2.4 and 2.5 present the estimated horizontal distribution of tritium in the vicinity of VB 6 in the shallow and deep zones of the overburden aquifer, respectively, in the winter of 2005. These figures indicate that the highest tritium concentrations were downgradient of VB 6.046907 (7)3 CONEsToGA-ROVERS

& AssocIATES

2.3 REMEDIAL

ACTION PLAN IMPLEMENTED AT VB 6 The remedial action plan selected for the VB 6 area and approved by the IEPA is MNA.The monitoring phase of the plan was designed to insure that the residual levels of tritium in groundwater did not further impair groundwater for current groundwater users (those outside the limits of the Station's property).

This monitoring program was specifically designed to assess and evaluate residual levels of tritium in groundwater.

Since the winter of 2005, Exelon has been monitoring tritium levels in groundwater near the VB 6 area. As a result, more than 3.5 years of data, including groundwater levels and tritium concentrations, has been collected.

More specifically, in September 2006, Exelon implemented routine quarterly groundwater monitoring as part of the Action Plan described above. Since implementation of the Action Plan, an additional 11 quarters of sampling data has been collected, analyzed, and submitted to the IEPA for evaluation.

This groundwater monitoring is in addition to the Nuclear Regulatory Commission (NRC) required groundwater sampling performed under the Station's Radiological Environmental Monitoring Program (REMP).Groundwater flow and tritium transport modeling performed at the VB 6 area was presented in the report prepared by CRA entitled "Groundwater Flow and Tritium Transport Modeling, Braidwood Generating Station" (CRA, August 2006). The modeling indicated that the tritium in the VB 6 area would not impact groundwater users off the Station property.

The modeling results presented in this report also suggest that 200 pCi/L would be reached within a few years at locations off the licensed property.2.4 CURRENT GROUNDWATER CONDITIONS The current trends of decreasing tritium concentrations within groundwater at the VB 6 area (January 2006 through May 2009) have been depicted on Figure 2.6 and in Table 2.1.Table 2.1 provides a summary of the statistical analyses of the monitoring wells sampled generally between the time period from January 2006 to May 2009. These analyses indicate a predominately downward trend of tritium concentrations in the groundwater monitoring wells in the vicinity of VB 6. Three monitoring wells in the VB 6 area were sampled and continue to indicate levels of tritium below the LLD of 200 pCi/L from January 2006 and May 2009 and therefore were excluded from the statistical analysis.046907 (7)4 CONEsToGA-ROVERS

& AssociATEs Two monitoring wells that have had tritium detected at concentrations greater than 200 pCi/L between January 2006 and May 2009 were utilized for statistical analysis.

The overall percent reduction of tritium concentrations between January 2006 and May 2009 is also presented in Table 2.1. Tritium concentrations have been reduced by as much as 100% from 520 pCi/L in September 2006 to less than the LLD of 200 pCi/L in May 2009, as shown at locations MW-148D and MW-150D. Groundwater samples collected from monitoring wells in the VB 6 area are at levels significantly below the drinking water standard of 20,000 pCi/L and, in fact, all sample data are currently less than the LLD of 200 pCi/L. Figure 2.6 presents the predominately downward trend in tritium concentrations over time at select monitoring wells in the VB 6 area.Figure 2.7 provides the September 2008 groundwater level contours.

Groundwater flow in the vicinity of VB 6 is generally towards the northeast.

Figure 2.8 provides the September 2008 estimated tritium results.Previous BIOSCREEN modeling in 2006 of the area indicated that tritium concentrations would not exceed 200 pCi/L beyond approximately 490 feet from the source concentration.

Previous modeling results estimated that steady state would be achieved in 15 years. In less than 2 years after the initial modeling results, all sampled monitoring well locations in the VB 6 area had tritium concentrations less than the LLD of 200 pCi/L.2.5 EVALUATION OF REMEDIAL ACTIVITIES TO DATE A review of the groundwater data, evaluations, and graphical presentations provided in Table 2.1 and on Figures 2.4 through 2.8 provides sufficient information to document the following: " There is no groundwater in this area that is above the drinking water standard of 20,000 pCi/L;" As of May 2009 tritium concentrations in all sampled monitoring wells in this area are less than the LLD of 200 pCi/L;* The average reduction in tritium concentrations per monitoring well is 100%;* With the exception of one out of two monitoring wells in this area utilized for statistical analysis, the trend in tritium concentrations in routine sampling events has been downward.

For one monitoring well a statistical trend could not be identified since the majority of results for that location were below LLD; and 046907 (7)5 CONESTOGA-ROVERS

& AssocIATES

• The maximum extent of tritium migration in the VB 6 area has been limited to less than 52 feet 2 from time of discovery in later 2005 and early 2006.Based on the results of the monitoring program, no detectable levels of tritium in groundwater above the LLD of 200 pCi/L, it is apparent that the MNA remedy proved successful in reducing tritium levels both on and off the Station property.2 The maximum extent was determined based upon the estimated plume length in 2006.046907 (7)6 CONEsToGA-ROVERS

& AssociATEs

3.0 CONCLUSION

S The previous sections of this Plan Completion Report have identified the nature and extent of tritium in groundwater near VB 6 and the progress of the remediation completed over the last 3.5 years. This information demonstrates the success of the cleanup of tritium in groundwater at VB 6 area.Specifically, the following remedial objectives have been met for the VB 6 area: " Concentrations of tritium in groundwater from the vacuum breaker releases are below the drinking water standard of 20,000 pCi/L; and* Any residual concentrations of tritium will not impact off-Site, private groundwater users; all monitoring wells are currently less than the LLD of 200 pCi/L.These remedial objectives are documented through the following facts: " All VB 6 area monitoring wells are below 20,000 pCi/L and have been since December 2005; and" All tritium concentrations as of May 2009 are below 200 pCi/L and have had a reduction of 100% since September 2006.046907 (7) 7 CON ESTOGA-ROVERS

& ASSOCIATES 046907 (7)7 CONESToGA-ROVERS

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4.0 PLANNED

COMPLETION ACTIVITIES Groundwater sampling and analyses for tritium at the VB 6 area will be eliminated, and all monitoring wells will be plugged and abandoned.

The monitoring wells to be abandoned are listed in Table 4.1.046907(7) 8 CONESTOGA-ROVERS

& AssociATEs 04607 (7)8 CONEsToGA-RovERs

& AssociATEs

5.0 REFERENCES

CRA, March 2006. Tritium Investigation, Exelon Generation

-Braidwood Station.CRA, March 2006, Interim Remedial Action Plan, Exelon Generation

-Braidwood Station.CRA, May 2006. Agreed Preliminary Injunction Order.CRA, June 2006. Migration Control Plan, Vacuum Breaker 1, Braidwood Generation Station, Braceville, Illinois.CRA, June 2006. Migration Control Plan, Vacuum Breakers 2 and 3, Braidwood Generation Station, Braceville, Illinois.CRA, August 2006. Groundwater Flow and Tritium Transport Modeling, Braidwood Generating Station, Braceville, Illinois.CRA, September 2006. Hydrogeologic Investigation Report, Fleetwide Assessment, Braidwood Generating Station.CRA, November 2006. Wedron Clay Till Investigation Report, Braidwood Generating Station, Braceville, Illinois.CRA, December 2006. CRA Memorandum, Transient Groundwater Flow Model Calibration and Transport Model Scenario Update.CRA, January 2007, 2006 Annual Groundwater Sampling Report, Tritium Remediation Program, Braceville, Illinois.Harbaugh, A.W. and M.G. McDonald, 1996a. User's Documentation for MODFLOW-96, an update to the U.S. Geological Survey Modular Finite-Difference Ground-Water Flow Model, United States Geological Survey Open-File Report 96-485, Reston, Virginia.Harbaugh, A.W. and M.G. McDonald, 1996b. User's Documentation for MODFLOW-96, an update to the U.S. Geological Survey Modular Finite-Difference Ground-Water Flow Model, United States Geological Survey Open-File Report 96-485, Reston, Virginia.McDonald, M.G. and A.W. Harbaugh, 1988. A modular Three-Dimensional Finite-Difference Ground-Water Flow Model, United States Geological Survey Open-File Report 83-875.Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, M.G., 2000. MODFLOW-2000, The U. S. Geological Survey Modular Ground-Water Model -User Guide To Modularization Concepts And The Ground-Water Flow Process, United States Geological Survey Open-File Report 00-92, Reston, Virginia.046907 (7)9 CONESTOGA-ROVERS

& AssociATEs Pollock, D.W., 1994. User's Guide for MODPATH/MODPATH-PLOT, Version 3: A particle tracking post-processing package for MODFLOW, the U.S. Geological Survey finite-difference ground-water flow model: U.S. Geological Survey Open-File Report 94-464.Sargent and Lundy, 1988. Updated Final Safety Analysis Report (UFSAR) Revision 1.0, December 1994. Chapters 2.4 and 2.5.Zheng, C., and P. Wang, 1999. MT3DMS: MT3DMS: A Modular Three-Dimensional Multispecies Transport Model for Simulation of Advection, Dispersion, and Chemical Reactions of Contaminants in Groundwater Systems; Documentation and User's Guide. Prepared by University of Alabama, Prepared for US Army Corps of Engineers.

048907(7) 10 CONESTOGA-ROVERS

& AssociATEs 046907(7)10 CONEsToGA-Rovms

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-IT MORRký,, ;rý CDl A )4 6txnx VS-I A Va-1-I 0 APPROXIMATE BLOWDOWN PROPERTY LINE SLOWDOWN LIE MAK(EUP LIE VACUUM BREAK(ER MID POINT MONITORING WELL LOCATION AND IDENTITjR VACUUM BREAKER MONITOJRING WELL LOCATION AND WDENIMER figure 1.2 LOCATION MAP FOR VB 6 AREA EXELON GENERATION BRAIDWOOD STATION Bra"vi/te, I/inois FOREST PRESERVE-- ----------------------

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410 201t VB-.6,o YAM V8-o MW-150O sovs4-"ID volmpVB-6-l MWl1 4 BOE VBd4-5 VB-6-~4 4-VE6 0 MW-48D VB--61)III L-23 VB-64D* V94B 0 ________VB-6630 LEGEND APPROXIMATE SLOWDOMWN PROPERTY LINE D EMW-14-D AUGUST 2006 PERMANENT MONITORING WELL LOCATION MAKUPLIN V___2 M WL.,BEENANDOWD figure 2.1 TREEUNE MONITORING WELL LOCATIONS

-VB 6 GROUNDWATER MONITORING PROGRAM VB-3 A VACUUM BREAKER LOCATION EXELON GENERATION BRAIDWOOD STATION BL-23 W B-WIWOOWN UNE MONITORING r=^,mdzo Illmih V S 54W r,,ss., SISI55~IC 46W07-00(07)N-C0003 AUG I111200 FOREST PRESERVE 0 10 20tt (V5 -.7 0(5a242)*V9-I-(582A3)V114 A Vs,.3-76 (512.42)LEGEND APPROXIMATE SLOWDOWN PROPERLY LIE SLOWDOWN LINE MAKEUP LINE TREELIN VACUUM BREAKER LOCATION SHAL.LOW VACUUM BREAKER SAMPUNG LOCATION GROUNDWATER ELEVATION (f AMSL)GROUNDWATER ELEVATION CONTOUR (3AUG14 GROUNDWATER FLOW DIRECTION figure 2.2 GROUNDWATER LEVEL CONTOURS -MARCH 2006 SHALLOW GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION (VB 6)Brnaiclle, Ilhmil 0 FOREST PRESERVE 0 10 20fm-----------------------------------

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VB-6-6D (582.46)VB-S-7D (582,43)0(582.26)5VB2-&D (58,08)VB-6-5D (682.34)( .VB-642D (SS2.63)_

VB6 5829 ( 582.42)VS-3iA V(5I-23 4 (511234)==82 LEGEND APPROXIMATE SLOWDOWN PROPERTY LINE SLOWDOWN LINE MAKEUP LINE VACUUM BREAKER LOCATION DEEP VACUUM BREAKER SAMPLING LOCATION GROUNDWATER ELEVATION (It AMSL)GROUONDWATER ELEVATION (ft AMSL)GROUNDWATER FLOW DIRECTION figure 2.3 GROUNDWATER LEVEL CONTOURS -MARCH 2006 DEEP GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION (VB 6)Braceavlle, Il/lins 4SW0-00OOTGN-C=5O AUG I1112=0 FOREST PRESER-IVE 0 10 20ft (NO)VB-S-i O(ND)Ve-49--VB-6-6 (ND4 (ND) VEI8 VS-6-3 LEGEND-APPROXIMATE BLOWDOWN PROPERTY LINE BLOWDOWN LINE MAKEUP LINE TREEUNE VB-3 A VACUUM BREAKER LOCATION Vs-3-70 SHALLOW VACUUM BREAKER SAMPLING LOCATION (2.125) TRIIUM RESULT IN GROUNDWATER pCIpL)-209-- TRITUM CONTOUR TRITIUM RESULTS 200 TO SA000 (pC.L)TRITIUM RESULTS 0 TO 200 (ND) NON-DOETECT BELOW 200 paYL NOTE.BACKGROUND TRITIUM CONCENTRATION:

200 pCV.DRINKING WATER STANARD FOR TRITIUM 20.000 paL MOST RECENT TRITUM RESULTS FOR SAMPLES COLLECTED THROUGH MARCH 2 2006. CONTOURS WERE GENERATED USING LOG VALUES.figure 2.4 ESTIMATED TRITIUM RESULTS -MARCH 2006 SHALLOW GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION (VB 6)Bracev/ole, Iliniois 4U0l74WW7)GN4XAUG IV2O 0 0 FOREST PRESERVE 0 10 205-- --------- ---------- -------------------------------------(NO)VB-oIU (NO)is IND)V(NO-i)(ND)(ND)(ND)LEGEND-APPROXIMATE BLOWDOWN PROPERTY UNE BLOWDOWN UNE MAKEUPL UNE TREELINE VB-3 A VACUUM BREAKER LOCATION VBS-1D 1 DEEP VACUUM BREAKER SAMPLNG LOCATION (79) TRITIUM RESULT IN GROUNDWATER (pCIL)(ND) NON-DETECT BELOW 200 pCUL NOTE: BACKGROUND TRITIUM CONCENTRATION:

200 pCIYL DRINKING WATER STANDARD FOR TRITIUM: 20.000 pCUL MOST RECENT TRITIUM RESULTS FOR SAMPLES COLLECTED THROUGH MARC4 6, 2006.figure 2.5 ESTIMATED TRITIUM RESULTS -MARCH 2006 DEEP GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION (VB 6)Bracevie, Illinois 41.Ji(7-UWJ7N-PJ AUG 11IrU FIGURE 2.6 TRITIUM CONCENTRATION TRENDS AROUND VB 6 AREA EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS 100000 10000 CL 0 0 0.E 1000 100 10--- MW-148D-MW-150D-20,000 pCVL-200 pCi/L 0 m D0 0000 00NNNNNN 0 0 0 E E-c m Date v4 0 175 350ft LEGEND VB-6 .A MW-15D *(595.43)LINE GROUNDWATER ELEVATION CONTOUR GROUDWATER FLOW DIRECTION VACUUM BREAKER LOCATION MONITORING WELL LOCATION AND IDEf GROUNDWATER ELEVATION (FT. AMSL)figure 2.7 GROUNDWATER LEVEL CONTOURS -VB 6 AND VB 7 AREAS SEPTEMBER 15-18, 2008 EXELON GENERATION BRAIDWOOD STATION Braceville, Illinois 469o7 (7)

FOREST PRES.RVE--------------------

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0 10 204 VS-" 71 VS4,870 MW-1500 (ND)am V84-"o VSB6-IDI ((ND)MW-149D thiml'LM148D6 v0~&4oS VD-6o V"4D V" \8-62D* B-* BL-23'wVS-6-3 Va-6-SO r-APPRO)XMATE SLOWWN PROPERTY LINE--S~~~LOWDOWN UNME~.AGS206PRAETM~lRIGWU OAI#MAKEUP UNE V842 I s .SHA E ORf r______figure

2.8 TEEEUNE

ESTIMATED TRITIUM RESULTS-SEPTEMBER 2008 Va-SA VACUUM BREAKER LOCAllON B6 G O N W T R Z E VB 6 GROUNDWATER ZONE M.-23 M EXELON GENERATION BRAIDWOOD STATION 4 U 0 7~(OO7QSCAUbG I IRM Bra~cevile, Illinois TABLE 2.1 Page 1 of 3

SUMMARY

OF TRITIUM STATISTICAL ANALYSES NEAR VB 6 EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Sample Date Result 1 (pCi/L)Percent Reduction 2 Minimum Maximum Sample Location Trend MW-148D MW-148D MW-148D MW-148D MW-148D MW-148D MW-148D MW-148D MW-148D MW-148D MW-148D MW-150D MW-150D MW-150D MW-150D MW-150D MW-150D MW-150D MW-150D MW-150D MW-150D MW-150D 9/11/2006 11/7/2006 3/15/2007 6/12/2007 9/13/2007 12/13/2007 3/11/2008 6/9/2008 9/16/2008 12/17/2008 3/12/2009 9/11/2006 11/7/2006 3/15/2007 6/11/2007 9/13/2007 12/13/2007 3/11/2008 6/9/2008 9/16/2008 12/17/2008 3/12/2009 477 227 ND ND ND ND ND ND ND ND ND 520 1555 1352 403 290 ND ND ND ND ND ND No trend identified 100%ND 477 Downward trend 100%ND 1555 Average Average MIN MAX Reduction 3 Downward trend 100% ND 1555.0 100%Non-Impacted Wells 4 BL-23 BL-23 BL-23 BL-23 BL-23 BL-23 BL-23 BL-23 BL-23 BL-23 6/2/2006 7/10/2006 8/15/2006 9/12/2006 10/10/2006 11/7/2006 12/11/2006 1/9/2007 2/14/2007 3/15/2007 ND ND ND ND ND ND ND ND ND ND CRA 0469( M TABLE 2.1 Page 2 of 3

SUMMARY

OF TRITIUM STATISTICAL ANALYSES NEAR VB 6 EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Sample Result' Percent Sample Location Date (pCi/L) Trend Reduction 2 Minimum Maximum BL-23 4/13/2007 ND BL-23 5/15/2007 ND BL-23 6/12/2007 ND BL-23 7/10/2007 ND BL-23 8/14/2007 ND BL-23 9/12/2007 ND BL-23 10/17/2007 ND BL-23 11/14/2007 ND BL-23 12/13/2007 ND BL-23 1/15/2008 ND BL-23 3/13/2008 ND BL-23 4/17/2008 ND BL-23 5/14/2008 ND BL-23 6/10/2008 ND BL-23 7/15/2008 ND BL-23 8/12/2008 ND BL-23 9/16/2008 ND BL-23 10/14/2008 ND BL-23 11/11/2008 ND BL-23 12/16/2008 ND BL-23 1/14/2009 ND BL-23 2/10/2009 ND BL-23 3/12/2009 ND BL-23 4/16/2009 ND BL-23 5/12/2009 ND MW-149D 9/11/2006 ND MW-149D 11/7/2006 ND MW-149D 3/15/2007 271 MW-149D 6/11/2007 ND MW-149D 9/13/2007 ND MW-149D 12/13/2007 ND MW-149D 3/11/2008 ND MW-149D 6/9/2008 ND MW-149D 9/16/2008 ND MW-149D 12/17/2008 ND MW-149D 3/12/2009 ND VB-6-1 12/20/2005 ND VB-6-1 1/3/2006 ND VB-6-1 7/11/2006 ND VB-6-1 8/15/2006 ND VB-6-1 9/11/2006 ND VB-6-1 10/9/2006 ND CRA 046907 TABLE 2.1 Page 3 of 3

SUMMARY

OF TRITIUM STATISTICAL ANALYSES NEAR VB 6 EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Sample Date Result'(pCVL)Percent Reduction 2 Minimum Maximum Sample Location Trend VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1.VB-6-1 VB-6-1 VB-6.-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 VB-6-1 11/7/2006 12/11/2006 1/9/2007 2/14/2007 3/15/2007 4/11/2007 5/15/2007 6/11/2007 7/9/2007 8/14/2007 9/12/2007 10/17/2007 11/13/2007 12/13/2007 1/15/2008 2/13/2008 3/11/2008 8/12/2008 9/16/2008 10/14/2008 11/11/2008 12/16/2008 1/13/2009 2/10/2009 3/12/2009 4/15/2009 5/12/2009 ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND Note: January 2006 data was used as initial concentrations for statistical analysis where available.

'Non-detect (ND) below 200 picocuries per liter (pCi/L).2 Monitoring Well locations with the most current data at ND were assumed to have 100% reduction.

3Average Reduction excludes well locations with a percent increase in concentration.

• Non impacted well were generally below or near the LLD and were excluded from statistical analysis.CPA 046907 (7)

TABLE 4.1 Page 1 of 1

SUMMARY

OF WELLS TO BE ABANDONED EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Vacuum Breaker Area Sample Location Vacuum Breaker 6 BL-23 MW-148D MW-149D MW-150D VB-6-1 CRA 046907(7)