RS-14-029, Plan Completion Report for the VB 7 Area
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PLAN COMPLETION REPORT FOR THE VB 7 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 FEBRUARY 2010 REF. NO. 046907 (8)This report is printed on recycled paper.Office: (773) 380-9933 Fax: (773) 380-6421 web: http:\\www.CRAworld.com TABLE OF CONTENTS Page
1.0 INTRODUCTION
..............................................................................................................
1 1.1 BACKGROUND AND PURPOSE ................................................................
1
1.2 DESCRIPTION
OF REMEDIATION AREA ...............................................
2 1.3
SUMMARY
OF REMEDIAL ACTIONS TO DATE AND CURRENT GROUNDWATER CONDITIONS
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2 2.0 CURRENT GROUNDWATER CONDITIONS AT VB 7 ...............................................
3 2.1 BACKGROUND
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3 2.2 PRE-REMEDIATION GROUNDWATER CONDITIONS
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3 2.3 REMEDIAL ACTION PLAN IMPLEMENTED AT VB 7 .........................
4 2.4 CURRENT GROUNDWATER CONDITIONS
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4 2.5 EVALUATION OF REMEDIAL ACTIVITIES TO DATE ............
6
3.0 CONCLUSION
S
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7 4.0 PLANNED COMPLETION ACTIVITIES
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8 5.0 R EFER EN C ES ..........................................................................................................................
9 046907 (8) CONESTOGA-ROVERS
& AssoclAns 046907 (8)CONESTOGA-ROVERS
& AssociATEs 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 FIGURE 2.9 SITE LOCATION MAP LOCATION MAP FOR VB 7 AREA MONITORING WELL LOCATIONS
-VB 7 GROUNDWATER LEVEL CONTOURS -JANUARY 2006 -SHALLOW GROUNDWATER ZONE GROUNDWATER LEVEL CONTOURS -JANUARY 2006 -DEEP GROUNDWATER ZONE ESTIMATED TRITIUM RESULTS -FEBRUARY 2006 -SHALLOW GROUNDWATER ZONE ESTIMATED TRITIUM RESULTS -FEBRUARY 2006 -DEEP GROUNDWATER ZONE TRITIUM CONCENTRATION TRENDS AROUND VB 7 AREA GROUNDWATER LEVEL CONTOURS -VB 6 AND VB 7 AREAS -SEPTEMBER 15-18, 2008 ESTIMATED TRITIUM RESULTS -SEPTEMBER 2008 -VB 7 GROUNDWATER ZONE BIOSCREEN MODEL PREDICTED VB 7 PLUME EXTENT TO BACKGROUND CONCENTRATION LIST OF TABLES
SUMMARY
OF TRITIUM STATISTICAL ANALYSES NEAR VB 7
SUMMARY
OF WELLS TO BE ABANDONED LIST OF APPENDICES TABLE 2.1 TABLE 4.1 APPENDIX A BIOSCREEN MODELING RESULTS (46907Memo-9) 046907 (8) CONESTOGA-ROVERS
& ASSOCIATES 046907(8)CONESTOGA-ROVERS
& AssocIATES
1.0 INTRODUCTION
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's LLC (Exelon) Braidwood Generating Station property located in Braceville, Illinois.'
More specifically, this Plan Completion Report addresses the Vacuum Breaker#7 (VB 7) 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 7 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 near Braidwood Station's VB 7 area. As a result, in November 2006, Exelon submitted a Minimize Impairment Plan, hereinafter referred to as the "Action Plan", for VB 7 to the IEPA. Upon the IEPA's approval of the Action Plan, the 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 1,000 picocuries per liter (pCi/L)in the VB 7 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 7 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 7 area is complete and can be concluded.
Section 5.0 of this Plan Completion Report provides a list of references specific to the VB 7 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.
' 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(8)1 CONESTOGA-ROVERS
& ASSOCIATES
1.2 DESCRIPTION
OF REMEDIATION AREA Land surrounding the VB-7 area falls mainly into the agricultural, residential, and recreational use categories (Figure 1.1). The center of the Village of Braidwood is approximately 11,000 feet from vacuum breaker VB 7. 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 VB 7 area is located approximately 14,000 feet east of the Braidwood Station. To the north and south of the Site is a forested area. 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 7 area utilizes passive techniques, which includes monitored natural attenuation (MNA). Groundwater flow and tritium concentrations are monitored quarterly and compared to predictive modeling.
At this location, the tritium detected in groundwater is declining and migrating as predicted through the BIOSCREEN groundwater models.The concentration of tritium in groundwater at monitoring wells in the VB 7 area has been reduced by as much as 100% since January 2006 (e.g., VB-7-1). As of September 2009, the highest tritium concentration detected at the VB 7 area was detected in MW-151D at a concentration of 779 pCi/L, substantially less than the federal drinking water standard of 20,000 pCi/L. With the exception of WCFPD-1D, the tritium concentrations detected in the monitoring wells continue to decline as a result of natural attenuation.
For WCFPD-1D no trend between January 2006 and September 2009 could be established.
WCFP-1D reached its peak tritium concentration of 1,480 pCi/L in March 2008 and has yet to provide a clear trend. This is likely due to the downgradient migration of the tritium as predicted by the BIOSCREEN groundwater model.046907 (8) 2 CONESTOGA-ROVERS
& ASSOCIATES 046907(8)2 CONESTOGA-ROVERS
& AssocIATES 2.0 CURRENT GROUNDWATER CONDITIONS AT VB 7 This section presents a description of the pre-remediation and current groundwater conditions at the VB 7 area.2.1 BACKGROUND Vacuum Breaker VB 7 is located on the blowdown line about 875 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.
Following the installation of the blowdown booster pump in 2003, flow in the line increased.
The increased flow raised the water level in the pipe at this vacuum breaker to the point where the valve would occasionally cycle to relieve air. Each time that a vacuum breaker cycles, it releases a small amount of water. Engineers estimated that this valve cycled every 5 minutes, releasing about 8 ounces of water each time.2.2 PRE-REMEDIATION GROUNDWATER CONDITIONS Since late 2005, a total of 23 monitoring wells have been installed into the deep and shallow zones of the overburden sand aquifer in the VB 7 Area. The majority of these monitoring wells have been abandoned.
Currently, there are five monitoring wells in the VB 7 area used for routine groundwater monitoring.
Figure 2.1 presents the monitoring well network in the vicinity of VB 7. 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 January 2006, respectively.
These figures indicate that groundwater in the vicinity of VB 7 flows generally north.Figures 2.4 and 2.5 present the February 2006 estimated horizontal distribution of tritium in the vicinity of VB 7 in the shallow and deep zones of the overburden aquifer, respectively.
These figures indicate that the highest tritium concentrations are downgradient of VB 7. The groundwater plume of tritium concentrations extends to the north from the valve.046907(8)3 CONESTOGA-ROVERS
& ASSOCIATES 2.3 REMEDIAL ACTION PLAN IMPLEMENTED AT VB 7 The remedial action plan selected for the VB 7 area and approved by the IEPA is MNA.The monitoring phase of this 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 7 area. As a result more than 4 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 14 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).The MNA remedy will ultimately reduce tritium levels both on and off the Station property to below the Lower Level of Detection (LLD) of 200 pCi/L or less than 1% of the established drinking water standard.
Groundwater levels and groundwater samples are currently collected at the VB 7 area on a quarterly schedule.Groundwater flow and tritium transport modeling performed at the VB 7 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 7 area would not impact groundwater users off the Station property.
The modeling results presented in this report also suggest that natural attenuation would reduce tritium concentrations to below 200 pCi/L within a few years at locations off the Station property.2.4 CURRENT GROUNDWATER CONDITIONS The current trends of tritium concentrations within groundwater at the VB 7 area (January 2006 through October 2009) have been depicted on Figure 2.6 and in Table 2.1.Table 2.1 provides a summary of the statistical analysis of the monitoring wells sampled generally between the time period from January 2006 to October 2009. These analyses indicate a downward trend of tritium concentrations in the groundwater monitoring 046907(8)4 CONESTOGA-ROVERS
& AssocIATES wells in the VB 7 area. Two monitoring wells in the VB 7 area were sampled and continued to indicate no detectable levels of tritium above the LLD of 200 pCi/L from January 2006 and October 2009 and therefore were excluded from the statistical analysis.Groundwater samples collected at three monitoring wells in the VB 7 area have contained tritium detected at levels above 200 pCi/L between January 2006 and October 2009, and these were utilized for statistical analysis.
Tritium concentrations have been reduced by as much as 92% from 10,055 pCi/L in September 2006 to 779 pCi/L in September 2009, as shown at location VB-7-1. Figure 2.6 presents the predominately downward trend in tritium concentrations over time at select monitoring wells in the VB 7 area.Figure 2.7 provides the September 2008 groundwater level contours.
Groundwater flow 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 62 feet from the source concentration.
Previous modeling results estimated that steady state would be achieved in 7 years. Data available at the time of the original BIOSCREEN model was limited due to the early status of the groundwater monitoring program. At the time of modeling the maximum tritium concentration at VB 7-1 was 349 pCi/L (February 2006), which was utilized as the source concentration.
That was the lowest historical tritium concentration for this monitoring well prior to October 2008. This low source concentration resulted in a lower estimate of the extent of tritium concentrations above 200 pCi/L.Groundwater sampling data collected in March 2009 (739 pCi/L) was recently utilized to run a BIOSCREEN model under more current groundwater conditions.
The model was run to determine the distance from the source area (WCFPD-1D) to the extent where the tritium concentrations are less than the LLD of 200 pCi/L. The more current BIOSCREEN results indicate that steady state is achieved in 9 years. The distance from the source area to areas with less than the LLD concentrations of tritium is approximately 136 feet. Figure 2.9 illustrates the predicted plume extent to the LLD.Appendix A presents the input and output of the more current BIOSCREEN modeling for this area.The nearest downgradient private well (PW-495-Creek) is located approximately 2,800 feet to the north from the predicted plume extent. Based upon modeling results, the private wells within the vicinity of VB 7 are not expected to be impacted by the plume (with tritium concentrations greater than 200 pCi/L) of tritium originating from the releases at VB 7. The residual levels of tritium in the groundwater in this area remain 046907 (8)5 CONESTOGA-ROVERS
& ASSOCIATES either on the Station property or on the WCFPD property where institutional controls and deed restrictions prohibit groundwater use.2.5 EVALUATION OF REMEDIAL ACTIVITIES TO DATE A review of the groundwater data, modeling evaluations, and graphical presentations provided in Table 2.1, on Figures 2.4 through 2.9, and in Appendix A 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;" The maximum concentration of tritium in this area, as of September 2009, is 779 pCi/L;* Only one monitoring well, WCFPD-1D, had an increase of 23% between January 2006 and September 2009; 2* Two out of five monitoring wells sampled during the quarterly sampling event in March 2009 indicated no detectable concentrations of tritium above the LLD of 200 pCi/L;* One of the five monitoring wells in the VB 7 area, located downgradient of the vacuum breaker, has shown an increase in tritium levels as predicted;" The limits of tritium in groundwater above the LLD of 200 pCi/L in September/October 2009 are restricted to Station property or property owned by the Will County Forest Preserve District; and* The BIOSCREEN modeled maximum extent of tritium migration in the VB 7 area is limited to less than 400 feet 3 from time of discovery in later 2005 and early 2006.2 This upward trend is consistent with modeling predictions.
3 Maximum extent determined by utilizing the distance between VB 7 and the BIOSCREEN maximum extent.046907 (8)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 7 and the progress of the remediation completed over the last 4 years. This information demonstrates the success of the cleanup of tritium in groundwater at the VB 7 area.Specifically, the following remedial objectives have been met for the VB 7 area: " Concentrations of tritium in groundwater from the vacuum breaker releases are below the drinking water standard of 20,000 pCi/L; and* Residual concentrations of tritium above 200 pCi/L will not impact off-Site, private groundwater users.These remedial objectives are documented through the following facts: " All VB 7 area monitoring wells are below 20,000 pCi/L and have been since December 2005;* The highest concentration of tritium as of September 2009 is 779 pCi/L (MW-151D)and has had a reduction of 92% since September 2006;* BIOSCREEN transport modeling of this area indicate that residual levels of tritium in groundwater will not migrate on to private property at levels above the LLD of 200 pCi/L; and" The closest private well receptor downgradient from predicted plume extent is approximately 2,800 feet.046907 (8) 7 CONESTOGA-ROVERS
& ASSOCIATES 046907(8)7 CONESTOGA-ROVERS
& ASSOCIATES 4.0 PLANNED COMPLETION ACTIVITIES Groundwater sampling and analyses for tritium at the VB 7 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 (8) 8 CONESTOGA-ROVERS
& ASSOCIATES 046907 (8)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, June2006.
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 96485, 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 96485, 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(8)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.
046907 (8) 10 CONESTOGA-ROVERS
& AssocIATEs 046907 (8)10 CONESTOGA-ROVERS
& AssocIATES J1~1)1~r 0 4000 800A LEGEND yBi-I A VACUUM BREAKER LOlCATION AND WETIFIER-BLOW 0OYM UNE figure 1.1 SITE LOCATION MAP EXELON GENERATION BRAIDWOOD STATION Brace,4lleo linois e (N.9 0j 100 00ft va-I A V_ B-1-1 ON LEGEND APPROXIMATE BLOWDOWN PROPERTY UNE BLOWDOWN UNE MAKEUP UNE VACUUM BREAKER MID POINT MONITORING WELL LOCATION AND IDENTIFIER VACUUM BREAKER MONITORING WELL LOCATION AND IDENTIFIER figure 1.2 LOCATION MAP FOR VB 7 AREA EXELON GENERATION BRAIDWOOD STATION Braceville, Illinois WCFPD1-20 VCFPLI-20& WCFPD-2DR WCF.7D-1 j50 FOREST PRESERVE-----------------------------------------------------------------------------------------------------
VB-7-3 IVB-74 VB-7-11) VB-7-1 MW'-151D BL-24 VB-7 VS 7 6Si VB-.-7D ]IV D VS7-V- -LEGEND APPROXIMATE BLOWDOWN PROPERTY UNE BLOWDOWN LINE MAKEUP UNE TREELINE VB-7 A, VACUUM BREAKER LOCATION BL-24 M BLOWDOWN LINE MONITORING VB-7-2 S SHALLOW VACUUM BREAKER SAMPLING LOCATION V/8-1D* SHADED WELL HAS BEEN ABANDONED W-1450 g AUGUST 2006 PERMANENT MONITORING WELL LOCATION W- 152D 0' PROPOSED MONITORING WELL LOCATION AND IDENTIFIER SVB-7-2 MY VS-7-1DI figure 2.1 MONITORING WELL LOCATIONS
-VB 7 GROUNDWATER MONITORING PROGRAM EXELON GENERATION BRAIDWOOD STATION Braceville, Illinois WELL HAS BEEN ABANDONED Al -4 4 -
56.WCFPD-2 , 30(50047)0 2i 0R FOREST PRESERVE VB-7-7 (682.91)VB-7-8 (582.77)I 6 VB-7 -------LEGEND --------------(582.03)-
VB-7 ?VS-3-7 6 (582.55)-F82.0--WCFPD-10 APPROXIMATE BLOWDOWN PROPERTY LINE BLOWDOWN UNE MAKEUP UNE TREELINE VACUUM BREAKER LOCATION SHALLOW VACUUM BREAKFR SAMPUNG LOCATION GROUNDWATER ELEVATION (ft AMSL)GROUNDWATER ELEVATION CONTOUR (it AMSL)GROUNDWATER FLOW DIRECTION WILL COUNTY FOREST PRESERVE TEMPORARY MONITORING WELL LOCATION figure 2.2 GROUNDWATER LEVEL CONTOURS -JANUARY 2006 SHALLOW GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION (VB 7)Braceville, Illinois WCFPD-2D (580.?0)WCFPD-ID (580.59) 581,00 2' 51ft FOREST PRESERVE--7-to -582.0 VB-..-- -582.5 V.,-7-ID (582.73)9VB-7-8D (582.61)APPROXIMATE BLOWDOWN PROPERTY LINE BLOWDOWN UNE MAKEUP LINE TREELINE figure 2.3 VE-7 A VACUUM BREAKER LOCATION VB-I-1D & DEEP VACUUM BREAKER SAMPLING LOCATION GROUNDWATER LEVEL CONTOURS -JANUARY 2006 (582.82) GROUNDWATER ELEVATION (It AMSL) DEEP GROUNDWATER ZONE-.O0- GROUNDWATER ELEVATION CONTOUR (ftAMWL) EXELON GENERATION BRAIDWOOD STATION (VB 7)GROUNDWATER FLOW DIRECTION Braweville, Illinois WCFPD-10D WILL COUNTY FOREST PRESERVE TEMPORARY MONMTORING WELL LOCATION 46907-00(008)GN-COM5 AUG 1112009
- WCFPD-2 (ND)(ND)OE0 20 REft FOREST PRESERVE VB-7-3 (ND) (ND)VB-7-5 VB-7-8 V B l.(M !& _ --& N D)(ND)~ ---A---------~
-*(ND)* V B ,-7 -7 (ND)VB-7-8 (ND)Vr-7 &VB-7-2 0 (26)-200----WCPD14 LEGEN.DD LEGEND VB-7-2 APPROXIMATE SLOWDOWN PROPERTY UINE VE(ND)MAKEUP LINE TREEUINE VACUUM BREAKER LOCATION SHALLOW VACUUM BREAKER SAMPLING LOCATION NOTE: TRITIUM RESULT IN GROUNDWATER (pCI/L) BACKGROUND TRITIUM CONCENTRATION:
200 pCIL TRITIUM CONTOUR DRINKING WATER STANDARD FOR TRITIUM: 20,000 figure 2.4 TRITIUM RESULTS 200 TO 5,000 WA) MOST RECENT TRITIUM RESULTS FOR SAMPLES TRITIUM RESULTS 0TO 200 FEBRUARY 2 0, .CONTOURS ESTIMATED TRITIUM RESULTS -FEBRUARY 2006 TR~lM ESLS T 20WERE GENERATED USING LOG VALUES. SHALLOW G O N W T RZONE WILL COUNTY FOREST PRESERVE TEMPORARY MONITORING WELL LOCATION FSYALLO G N TE NON-ETEC GENERATED USING VT IN( 7)NON'DETECT BELOW 200pC/IL, .I (1w (ND)...... .),'B ,IAW OOD STATION (V1 0 7)
WcFPD-2D*WCFPD.ID (ND)(ND) E 0 20 5011 FOREST PRESERVE-------------------- -7 ,VB-7-7D (ND)*VB-7-SD (ND)----------LEGEND------APPROMiMATE SLOWDOWN PROPERTY UINE SLOWDOWN UNE MAKEUP LINE TREEUNE NOTE: VS-7 A VACUUM BREAKER LOCATION BACKGROUND TRITIUM CONCENTRATION:
200 pCVL VI-D DEP VACUUM BREAKER S G LOCAT IDRINKING WATER STANDARD FOR TRITIUM: 20.000 pCI/L 1200 DEEP VACUUM BREAKER SAMPLING LOCATION MOST RECENT TRITIUM RESULTS FOR SAMPLES (339) TRITIUM RESULT IN GROUNDWATER (pa/L) COLLECTED THROUGH FEBRUARY 20. 2005. CONTOURS R L FurY TRITIUM CONTOUR WERE GENERATED USING LOG VALUES ESTIMATED TRITIUM RESULTS -FEBRUARY 2006_ TRITIUM RESULTS 200 TO 5,000 (pClL)NWC)PD-1@
WILL COUNTY FOREST PRESERVE TEMPORARY MONITORING WELL LOCATION EXELON GENERATION BRAIDWOOD STATION (VB 7)(N) NON-OETECT BELOW 200 pCJI. EEO E E AINB AD O DSAIN(B7 (ND)o BL 2B6aceVlle, Illinois FORE 2.6 TRITIUM CONCENTRATION TRENDS AROUND VB 7 AREA EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS 100000 10000 C-)0.0 0 E 4-1000--- MW-151D a VB-7-1-4-- WCFPD-1D-20,000 pCi/L-200 pCi/L 100 10 C.O CoD ,D CO CD CD CO CD(O Co C LL C 0-0)co)co Co 00 E E 0)0>0 004)r- N- r- r- N. N 0 0 0000:,~W U-99999-9990009999---9'-999--9999
~.0flffl CU U... r 75 M ~.0f .0 J, M U M .~ .~E 2E E 2 E .2 E E E 2 E ..2) 0 ) ..Date CO 0 0.0 E 0)0 z 046907(8) 0 175 3505t LEGEND BLOWDOWN LINE GROUNDWATER ELEVATION CONTOUR GROUDWATER FLOW DIRECTION VB-6 .VACUUM BREAKER LOCATION MW-15D
- MONITORING WELL LOCATION AND IDENTIFIER (595.43) 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 46907(8)
WCFPD-2 5 WCFPD-21'*WCFPD-2DR (ND)WCFPD-1O~(894)420 50ft FOREST PRESERVE----------------------
-------------
VB-i7-1 (1,080)a VB--74 BL-21 (ND)B YB7 67S 5 V' 7 -VB-?-iD 11 YB4-7 YB-7-8Iw YE-i-8 --LEGEND--- -- -- APPRO)OMATE SLOWDOWN PROPERTY UINE---SLOWDOWNULNE MAKEUP UINE MAKEUP UINE VB-i A BL-24 M VB-7-2 49 MW-151D 0 PWN-106 YB-i-ID W (417)(ND)VACUUM BREAKER LOCATION BLOWDOWN UNE MONITORING SHALLOW VACUUM BREAKER SAMPUNG LOCATION AUGUST 2006 PERMANENT MONITORING WELL LOCATION PRIVATE WELL LOCATION AND IDENTIFIER WELL HAS BEEN ABANDONED SEPTEMBER 2008 TRITIUM DATA (PCI.L)NON DETECT S VB-7-2 figure 2.8 ESTIMATED TRITIUM RESULTS-SEPTEMBER 2008 VB 7 GROUNDWATER ZONE EXELON GENERATION BRAIDWOOD STATION Braceville, llinois 46907400(008)GN-C0009 AUG 11/2009 0 PW-495-CreeIk (D 9 FOREST PRESERVE LEGEND B1,24 M VB-7-1 19 MW-S1O1 0 PWN-106 00*UUUU U Umpo m APPROXIMATE SLOWDOWN PROPERTY LINE BLOWDOWN LINE MAKEUP LINE VACUUM BREAKER LOCATION BLOWDOWN LINE MONITORING SHALLOW VACUUM BREAKER SAMPLING LOCATION AUGUST 2006 PERMANENT MONITORING WELL LOCATION PRIVATE WELL LOCATION AND IDENTIFIER PREDICTED EXTENT OF TRITIUM PLUME ABOVE BACKGROUND CONCENTRATION (200 pCVL)' f4 00a figure 2.9 BIOSCREEN MODEL PREDICTED VB 7 PLUME EXTENT TO BACKGROUND CONCENTRATION EXELON GENERATION BRAIDWOOD STATION Braceville, Illlno/s TABLE 2.1 Page 1 of 4
SUMMARY
OF TRITIUM STATISTICAL ANALYSES NEAR VB 7 EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Sample Percent Sample Location Date Result' Trend Reduction 2 Minimum Maximum MW-151D 9/11/2006 10055 MW-151D 11/6/2006 10804 MW-151D 3/15/2007 4850 MW-151D 6/11/2007 2873 MW-151D 9/13/2007 2129 MW-151D 12/13/2007 4010 MW-151D 3/11/2008 2370 MW-151D 6/9/2008 1330 MW-151D 9/16/2008 1080 MW-151D 12/16/2008 1470 MW-151D 3/11/2009 802 MW-151D 6/8/2009 ND MW-151D 9/15/2009 779 Downward trend 92% ND 10804 VB-7-1 12/20/2005 1612 VB-7-1 12/22/2005 2358 VB-7-1 1/3/2006 2776 VB-7-1 2/20/2006 349 VB-7-1 7/10/2006 4462 VB-7-1 8/15/2006 5850 VB-7-1 9/11/2006 4174 VB-7-1 10/9/2006 1823 VB-7-1 11/6/2006 1513 VB-7-1 11/29/2006 1318 VB-7-1 12/11/2006 1266 VB-7-1 1/9/2007 1449 VB-7-1 2/14/2007 1604 VB-7-1 3/14/2007 1628 VB-7-1 4/11/2007 1321 VB-7-1 5/16/2007 704 VB-7-1 6/11/2007 732 VB-7-1 7/10/2007 882 VB-7-1 8/14/2007 1357 VB-7-1 9/12/2007 1085 VB-7-1 10/17/2007 1480 VB-7-1 11/13/2007 998 VB-7-1 12/13/2007 928 VB-7-1 1/15/2008 670 VB-7-1 2/12/2008 435 VB-7-1 3/11/2008 745 VB-7-1 4/15/2008 528 VB-7-1 5/13/2008 691 VB-7-1 7/16/2008 499 CRA 046907 (8)
TABLE 2.1 Page 2 of 4
SUMMARY
OF TRITIUM STATISTICAL ANALYSES NEAR VB 7 EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Sample Date Percent Reduction 2 Sample Location Result I Trend Minimum Maximum VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 VB-7-1 WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D WCFPD-1D 8/12/2008 9/16/2008 10/14/2008 11/11/2008 12/16/2008 1/13/2009 2/10/2009 3/11/2009 4/15/2009 5/13/2009 6/8/2009 7/13/2009 8/12/2009 9/15/2009 10/13/2009 11/11/2009 1/12/2006 3/15/2007 6/13/2007 9/13/2007 12/14/2007 3/11/2008 6/10/2008 9/18/2008 12/16/2008 3/12/2009 6/9/2009 9/15/2009 621 417 314 356 316 341 702 619 ND ND ND ND ND ND 297 250 ND ND ND ND 690 1480 406 894 485 739 255 260 Downward trend 91%ND 5850 No trend identified
-23%ND 1480 Non-Impacted Wells 3 BL-24 BL-24 BL-24 BL-24 6/2/2006 7/24/2006 8/15/2006 9/13/2006 ND ND ND ND CRA 046907 (8)
TABLE 2.1 Page 3 of 4
SUMMARY
OF TRITIUM STATISTICAL ANALYSES NEAR VB 7 EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Sample Percent Sample Location Date Result' Trend Reduction 2 Minimum Maximum BL-24 10/10/2006 ND BL-24 11/6/2006 ND BL-24 12/11/2006 ND BL-24 1/9/2007 ND BL-24 2/14/2007 ND BL-24 3/12/2007 ND BL-24 4/11/2007 ND BL-24 5/16/2007 ND BL-24 6/12/2007 ND BL-24 7/10/2007 ND BL-24 8/14/2007 ND BL-24 9/12/2007 ND BL-24 9/12/2007 269 BL-24 9/26/2007 ND BL-24 10/17/2007 ND BL-24 11/14/2007 ND BL-24 12/13/2007 ND BL-24 1/16/2008 ND.BL-24 2/13/2008 ND BL-24 3/11/2008 ND BL-24 4/15/2008 ND BL-24 5/14/2008 ND BL-24 6/10/2008 ND BL-24 7/16/2008 ND BL-24 8/13/2008 ND BL-24 9/18/2008 ND BL-24 10/14/2008 ND BL-24 11/11/2008 ND BL-24 12/16/2008 ND BL-24 1/14/2009 ND BL-24 2/10/2009 ND BL-24 3/12/2009 ND BL-24 4/16/2009 ND BL-24 5/13/2009 ND BL-24 6/8/2009 ND BL-24 7/13/2009 ND BL-24 8/12/2009 ND BL-24 9/15/2009 ND BL-24 10/13/2009 ND BL-24 11/11/2009 ND WCFPD-2DR 3/15/2007 ND O WCFPD-2DR 6/13/2007 ND WCFPD-2DR 9/13/2007 ND CRA 046907 (8)
TABLE 2.1 Page 4 of 4
SUMMARY
OF TRITIUM STATISTICAL ANALYSES NEAR VB 7 EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Sample Date Percent Reduction 2 Minimum Maximum Sample Location WCFPD-2DR WCFPD-2DR WCFPD-2DR WCFPD-2DR WCFPD-2DR WCFPD-2DR WCFPD-2DR WCFPD-2D Result'Trend 12/14/2007 3/11/2008 6/10/2008 9/18/2008 12/16/2008 3/12/2009 6/9/2009 9/15/2009 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 pCi/L.Monitoring Well locations with the most current data at ND were assumed to have 100% reduction.
'Non impacted well were generally below or near ambient levels and were excluded from statistical analysis.CRA 046907 (8)
TABLE 4.1 Page 1 of 1
SUMMARY
OF WELLS TO BE ABANDONED EXELON GENERATION BRAIDWOOD STATION BRACEVILLE, ILLINOIS Vacuum Breaker Area Vacuum Breaker 7 Sample Location BL-24 MW-151D VB-7-1 WCFPD-1D WCFPD-2DR CRA 046907 (8)
APPENDIX A BIOSCREEN MODELING RESULTS 046907(8)
CONESTOGA-ROVERS
& ASSOCIATES 8615 W. Bryn Mawr Avenue, Chicago, Illinois 60631 Telephone:
(773) 380-9933 Fax: (773) 380-6421 www.CRAworld.com MEMORANDUM TO: File REF. NO.: 046907 FROM: Kristine White/ko/9 DATE: February 22, 2010 RE: Modeling of Tritium Migration in Groundwater in VB 7 Area Using BIOSCREEN Braidwood Generating Station Braceville, Illinois The purpose of this memorandum is to present results of an evaluation of the potential off-Site migration of tritium in groundwater downgradient of Vacuum Breaker # 7 (VB 7) at Braidwood Station (Site). The site-specific hydrogeological information was used to predict the plume extent.BIOSCREEN The analytical solute transport model BIOSCREEN, developed by the United States Environmental Protection Agency (USEPA) for use at petroleum hydrocarbon release sites (USEPA, 1996; and Newell et al., 1997), was used for this study. BIOSCREEN is a two-dimensional solute transport model that simulates the processes of solute advection, dispersion, adsorption, and first-order decay under uniform groundwater flow conditions.
The analytical solute transport model developed by Domenico (1987) forms the basis of the solution in BIOSCREEN.
In this particular study, the radioactive decay process of tritium was modeled using the first-order biodegradation term available in BIOSCREEN.
BIOSCREEN requires data entry including an average linear groundwater flow velocity, contaminant dispersivity, retardation and biodegradation (or radioactive decay, in this case) constants, and a source area condition (including the source size and source concentration).
BIOSCREEN then calculates contaminant concentrations in groundwater at a specified time along the plume centerline over a specified distance downgradient from the source area. BIOSCREEN allows the entry of observed contaminant concentrations at specified distances down gradient from the sources area to which the calculated plume centerline concentration and concentration may be compared.
BIOSCREEN also calculates contaminant concentrations in groundwater in the transverse direction.
MODEL SETTINGS Parameters related to the hydrogeological properties for the modeling analysis are described below.Figure 1 shows the BIOSCREEN input parameters.
Further details of the parameters are described in the following paragraphs.
fIIGISTlO COMPABY FOR ISO 9001 EQUAL EMPLOYMENT OPPORTUNITY EMPLOYER ENGINEEAIUG DEfSlWN CRA MEMORANDUM Page 2 Seepage Velocity The seepage velocity (Vs) at the Site was found to be 175.0 ft/year, which was based on the following equation: Vs =K-i/ne Where, K is the hydraulic conductivity, which was set to 0.0254 centimeters per second (cm/s) (or 72 ft/day)based on slug tests performed at the Site in October 2005;i is hydraulic gradient, which was set to be 0.002 ft/ft, estimated based upon January-March 2006 groundwater contours downgradient of VB7; and n, is the effective porosity, which was set to be 0.30 based on literature range for the fine to medium sand (Domenico and Schwartz, 1990).Dispersivities Longitudinal and transverse dispersivity were estimated using an empirical relationship between the plume length and dispersivity.
The following relationships were utilized to determine dispersivities (USEPA, 1996): a. 3.28- 0.83. log 10 ( )-.1 (Xu and Eckstein, 1995)=3.280.8 logo3.28 ay= 0.10 a, (Based on high reliability points from Gelhar et al., 1992)a= 0.025 a. to 0.1 a, (EPA, 1986)Based on the above relationships, the longitudinal disversivity (a.) was found to be 24.5 ft, based upon an potential plume length (Lp) of 1000 ft; the transverse dispersivity in Y direction (ay) was 2.4 ft; and the vertical dispersivity (az) was 1.2 ft.Adsorption Adsorption process is represented as a retardation factor in the BIOSCREEN model. A retardation factor of 1.0 (i.e., no retardation) was used in this simulation, since tritium binds readily with oxygen to form TOH or T20 molecules and therefore travels at the same speed as groundwater would.Radioactive Decay Tritium decays naturally over time. The degradation process can be represented by a first order differential equation expressed as: ac at CRA MEMORANDUM Page 3 Here, c is the aqueous concentration of tritium (picoCuries per liter, or pCi/L), and t is time (years). X is the Sfirst-order decay rate (1/year) that is related to the half-life, t/, (years), by the following equation: A = In(2) 0.693 tl/2 t1/2 The natural radioactive decay rate for tritium was found to be 5.6 X 10-2 per year.Model Domain The model length was set at 136 ft (of which was the preliminary plume extent) and the model width was set at 300 ft in order to encompass the entire extent of the plume to 200 pCi/L.Tritium Source Settings Based on the existing observed source conditions at VB 7, the tritium concentration of 739 pCi/L collected in March 2009 from WCFPD-1D was utilized as the source concentration.
The source thickness was estimated to be 10 ft and the source width was estimated to be 50 ft.Simulation Time A simulation time of 10 years was selected to ensure the plume can be stabilized within the selected time frame. BIOSCREEN was run to steady-state to determine what the concentration of tritium would be downgradient of the source.MODEL RESULTS The background level for tritium established for the area is 200 pCi/L. The model was run to determine the distance from the source to the points where the background tritium concentrations are met, and plume widths at various distances.
A steady-state was achieved in 9 years. Figure 2 presents the simulated tritium concentration vs. distance.As shown on Figure 2, the distance from the source to tritium background concentration of 200 pCi/L is approximately 136 feet as a maximum tritium extent downgradient of VB 7.REFERENCES Domenico, P. A. An Analytical Model for Multidimensional Transport of a Decaying Contaminant Species, Journal of Hydrology, 91, pp. 49-58, 1987.Domenico, P.A. and F.W. Schwartz, Physical and Chemical Hydrogeology, John Wiley & Sons, Inc. 1990.Newell, J. c., R. K. McLeod, and J. R. Gonzales.
BIOSCREEN:
Natural Attenuation Decision Support System 0 -Version 1.4 Revisions.
Groundwater Services, Inc., Air Force Center for Environmental Excellence, July 1997.
CRA MEMORANDUM Page 4 Nicholas, J. R. and R. W. Healy. Tritium Migration from a Low-Level Radioactive-Waste Disposal Site Near Chicago, Illinois U. S. Geological Survey Water-Supply Paper 2333, Denver, CO, 1988. 4 USEPA. BIOSCREEN:
A Natural Attenuation Decision Support System User's Manual Version 1.3 EPA Report No. EPA/600/R-96/087, Office of Research and Development, Cincinnati, OH, 1996.USEPA. EPA -Tritium -Information Page. www.epa.gov/radiation/radionuclides/tritium.htm, November 30,2004, accessed on February 14, 2006.
raidwood 2.4 4-)0.7 16.6 22.4 RUN CENTERLINE View Output RUN ARRAY Help RecalculateH This e ESheet Paste Example Dataset View Output Restore Formulas for Vs, Dispersivities, R, lambda, other figure 1 BIOSCREEN INPUT PARAMETERS EXELON GENERATION BRAIDWOOD STATION Braceville, Illinois 046907(8)
TRITIUM CONCENTRATION ALONG PLUME CENTERLINE (pCiIL at Z=0)Distance from Source (ft)TYPE OF MODEL 0 14 27 41 54 68 82 95 109 122 136 1st Order Decay 739.000 673.134 553.750 459.748 389.691 336.731 295.687 263.095 236.655 214.809 196.472 figure 2 CONCENTRATION FOR TRITIUM SOURCE OUT TO BACKGROUND CONCENTRATION EXELON GENERATION BRAIDWOOD STATION Braceville, Illinois 04978 w w 046907 (8) L--W