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{{#Wiki_filter:PLAN COMPLETION REPORT FOR THE VB 2/3 ANDPOND AREABRAIDWOOD GENERATION STATIONBRACEVILLE, ILLINOISPrepared For:Exelon Generation
: Company, LLCDISCLAIMER:
SOME FORMATTING CHANGES MAY HAVE OCCURRED WHENTHE ORIGINAL DOCUMENT WAS PRINTED TO PDF; HOWEVER,THE ORIGINAL CONTENT REMAINS UNCHANGED.
Prepared by:Conestoga-Rovers
& Associates 8615 West Bryn MawrChicago, Illinois 60631DECEMBER 2012REF. NO. 016841 (45)This report is printed on recycled paper.Office: (773) 380-9933Fax: (773) 380-6421web: http:\\www.CRAworld.com 4TABLE OF CONTENTSPage
==1.0 INTRODUCTION==
AND PURPOSE .............................................................
12.0 DESCRIPTION OF REMEDIATION
.................................................................................
32.1 DESCRIPTION OF VB 2/3 AND POND AREA ..........................................
32.2 REM EDIAL OBJECTIVES
............................................................................
32.3 PRE-REMEDIATION CONDITIONS
...........................................................
42.4 ACTION PLAN IMPLEMENTATION
-GROUNDWATER PUMPING .... 43.0 CURRENT GROUNDWATER CONDITIONS AT THE VB 2/3 AND POND AREA... 63.1 CURRENT GROUNDWATER QUALITY CONDITIONS
........................
63.2 CURRENT GROUNDWATER FLOW CONDITIONS
................................
83.3 COMPARISON OF CURRENTGROUNDWATER QUALITY CONDITIONS TO HISTORICAL DATA ..... 93.4 EVALUATION OF THE REMEDIAL ACTION ...................
93.5 EVALUATION OF FUTURE GROUNDWATER CONDITIONS
...............
104.0 CO N CLU SIO N S .....................................................................................................................
125.0 PLANNED COMPLETION ACTIVITIES
.....................................................................
136.0 REFEREN CES .........................................................................................................................
14016841 (45) CONESTOGA-ROVERS
& ASSOCIATES 016841 (45)CONESTOGA-ROVERS
& Assoc[ATES LIST OF FIGURESFIGURE 2.1FIGURE 2.2FIGURE 2.3FIGURE 2.4FIGURE 2.5FIGURE 2.6FIGURE 3.1FIGURE 3.2FIGURE 3.3FIGURE 3.4FIGURE 3.5FIGURE 3.6FIGURE 3.7FIGURE 3.8FIGURE 3.9FIGURE 3.10VB 2/3 AND POND AREA SITE LOCATION MAPLOCATION MAP FOR VB 2/3 AND POND AREAMONITORING WELL AND PRIVATE WELL LOCATIONS
-VB 2/3 ANDPOND AREAGROUNDWATER LEVEL CONTOURS
-JANUARY 2006 -DEEPGROUNDWATER ZONEESTIMATED TRITIUM RESULTS -JANUARY 2006 -DEEPGROUNDWATER ZONECURRENT RESIDENTIAL SAMPLING LOCATIONS INDEX OF VB 2/3 AND EXELON POND AREA LOCATIONS TRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THEVB 2 AREATRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THEBL-06 AREATRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THERW-9 AND RW-10 AREATRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THEVB 3 AREATRITIUM CONCENTRATION TRENDS IN MONITORING WELLSNORTHEAST OF PONDTRITIUM CONCENTRATION TRENDS IN MONITORING WELLSNORTHWEST OF PONDTRITIUM CONCENTRATION TRENDS IN MONITORING WELLSSOUTHEAST OF PONDTRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THELEADING EDGEGROUNDWATER CONTOURS
-JUNE 2012016841 (48) CONESTOGA-ROVERS
& ASSOCIATES 016841 (45)CONESTOGA-ROVERS
& Assoc[ATES LIST OF FIGURES0FIGURE 3.11FIGURE 3.12FIGURE 5.1CONCENTRATION OF TRITIUM IN GROUNDWATER
-JUNE 2012JANUARY 2006 TRITIUM PLUME VS JUNE 2012 RESIDUAL TRITIUMRGPP MONITORING WELL LOCATIONS IN THE VB 2/3 AND PONDAREA016841 (45) CONESTOGA-ROVERS
& ASSOCIATES 016841 (45)CONEsToGA-ROVERS
& AsSOCIATES LIST OF TABLESTABLE 3.1TABLE 5.1TABLE 5.2SUMMARY OF RECENT TRITIUM ANALYSIS IN MONITORING WELLSNEAR VB 2/3 AND POND AREASUMMARY OF CURRENT RGPP MONITORING WELLS IN THE VB 2/3AND POND AREASUMMARY OF MONITORING WELLS TO BE ABANDONED 016841 (45) CONESTOGA-ROVERS
& ASSOCIATES 016841(45)
CONEsToGA-ROVERS
& AssoclATES LIST OF APPENDICES APPENDIX AAPPENDIX BAPPENDIX CSUMMARY OF TRITIUM ANALYSIS AT PRIVATE WELLS AND PONDSSUMMARY OF TRITIUM ANALYSES IN MONITORING WELLS NEARVB 2, VB 3, THE EXELON POND AND THE LEADING EDGE AREASGROUNDWATER MODELING RESULTS (Memorandum) 016841 (45) CONESTOGA-ROVERS
& ASSOCIATES 016841 (45)CONEsToGA-ROVERS
& Assoc[ATES EXECUTIVE SUMMARYThis document demonstrates the successful completion of the remediation of tritium inshallow groundwater at the Exelon Generation Company LLC's (Exelon)
Braidwood Generating Station property (Station) in Braceville, Illinois 1, specifically in the VacuumBreaker 2/3 and Pond (VB 2/3 and Pond) area. Groundwater which had previously been impacted by tritium released from the Station's Blowdown Line has been cleanedup to safe levels through the use of active pumping and monitored natural attenuation.
In accordance with the March 11, 2010 Agreed Consent Order, this document presentsthe Plan Completion Report for the VB 2/3 and Pond Area. This Plan Completion Report fully describes the implementation, identifies any corrective action goals thathave been met, and demonstrates the efficacy of the remedy as implemented.
In late 2005 and early 2006, surface water and groundwater investigations led to thediscovery of elevated tritium concentrations in the groundwater in the VB 2/3 and Pondarea. The elevated tritium concentrations in the groundwater were attributed to leaks inthe vacuum breaker valves. The leaks were subsequently repaired.
In order toremediate the groundwater in the VB 2/3 and Pond area, Exelon initiated activeremediation through the pumping of the Exelon Pond in June 2006 and the pumping ofrecovery wells RW-9 and RW-10 in January 2008.Through active remediation, tritium concentrations in groundwater in this area havedecreased significantly between January 2006 and June 2012. Tritium concentrations inJanuary 2006 were as high as 228,283 picocuries per liter (pCi/L) (at monitoring wellP-13D), while in June 2012, the maximum tritium concentration detected was 945 pCi/L(at monitoring well P-4D). The active remediation significantly decreased tritiumconcentrations in the groundwater to below the drinking water standard (20,000 pCi/L)and has prevented further migration of tritium in groundwater off Exelon-owned property at concentrations greater than the lower limit of detection (LLD) of 200 pCi/L.The data, evaluations, and modeling contained in this Plan Completion Report lead tothe following conclusions which support the closure of all remedial activities at theVB 2/3 and Pond area.'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 byExelon along Smiley Road and Center Street.016841(45)
CONEsToGA-ROVERS
& AssocIATES
* The maximum concentrations of residual tritium in groundwater in the VB 2/3 andPond area as of June 2012 are less than 5% of the US EPA's drinking water standardof 20,000 pCi/L; and" As demonstrated by predictive
: modeling, the residual levels of tritium in theVB 2/3 and Pond area will not migrate further off the Station's licensed propertyand onto private property at levels above the LLD of 200 pCi/L.016841 (45) ii CONESTOGA-ROVERS
& AssociATEs 016841 (45)HiCONEsToGA-ROVERS
& AsSOCIATES
==1.0 INTRODUCTION==
AND PURPOSEThis Plan Completion Report has been prepared for the Illinois Environmental Protection Agency (IEPA) to address groundwater remediation regarding the VacuumBreaker 2/3 and related Pond area at the Exelon Generation Company LLC's (Exelon)Braidwood Generating Station property located in Braceville, Illinois.
Specifically, thisReport discusses the groundwater investigation, monitoring, and remedial actions thatwere implemented in accordance with the Agreed Preliminary Injunction Order (PIO)dated May 24, 2006, and the March 11, 2010 Agreed Consent Order (ACO), entered intoby Exelon and the State of Illinois.
Information collected to date as a result of ActionPlan implementation is sufficient to determine that remediation at the VB 2/3 andExelon Pond area is complete and can be concluded.
These orders refer to a number of "Action Plans" necessary to remediate groundwater impacted by tritium to levels below the drinking water standard
[20,000 picocuries perliter (pCi/L)]
and then to levels below agreed upon background levels (200 pCi/L)which is represented by the lower limit of detection (LLD).The first Action Plan generated for the VB 2/3 and Pond Area was the June, 2006"Migration Control Plan, Vacuum Breakers 2 and 3". This plan involved the pumping ofthe Exelon Pond and the prevention of tritium migrating off of Exelon's property atlevels above the drinking water standard (20,000 pCi/L). The second Action Plandeveloped for the VB 2/3 and Pond Area was the November 2006 "Minimize Impairment Plan for Vacuum Breakers 2 and 3". This (Minimize Impairment) plan was to beimplemented if tritium remained for a significant time period at concentrations belowthe drinking water standard, but above the LLD at locations off the Exelon Property.
This plan has not been implemented as the remedial efforts have been successful insignificantly reducing tritium in groundwater.
Current modeling (Section 3.5) indicates that any residual tritium remaining in groundwater will be mitigated by naturalattenuation to concentrations below the LLD of 200 pCi/L before it migrates from itsexisting location to adjacent properties.
This Report presents the data gathered to demonstrate that the remedial efforts in theVB 2/3 and Pond area have been successful and that all required objectives provided inthe Action Plans of the PIO and ACO have been met. All tritium concentrations arecurrently below 1,000 pCi/L, and future predictive modeling indicates that tritium willnot migrate further off the Station's property at concentrations greater than the LLD of200 pCi/L, even after all pumping activities have stopped.
As such, remediation isconsidered complete for this area.016841 (45)ICONESTOGA-ROVERS
& ASSOCIATES The PIO and ACO were put into place as a result of several tritium leaks detected byExelon. In 1998 and 2000, leaks originating from the vacuum breakers were detectedand subsequently repaired.
In the spring of 2005, following the detection of tritiumabove ambient levels in the perimeter ditch, Exelon investigated shallow groundwater on the east side of the Station, in areas along Smiley Road and Center Street, and alongthe Station's blowdown line. As a result of these investigations, the vacuum breakerswere repaired and active remediation in the VB 2/3 and Pond area was initiated.
Aspresented in the June 2006 Migration Control Plan, the remediation in the VB 2/3 andPond area included pumping of the Exelon Pond. The pumping of the Exelon Pond wasinitiated in June 11, 2006. In January 2007, elevated tritium concentrations were detectedin the area near monitoring well BL-06 (south of the pond). Exelon installed tworecovery wells (RW-9 and RW-10) north of BL-06 in November 2007. RW-9 and RW-10began pumping in January 2008. Since 2006, Exelon has developed an extensive monitoring well network in the VB 2/3 and Pond area in order to monitor tritiumconcentrations.
Select monitoring wells are monitored on a quarterly basis for tritiumconcentrations and for water levels.Since the initiation of these remedial activities, Exelon has pumped over 700,000,000 gallons of water from the Exelon Pond in support of its remedial activities at theVB 2/3 and Pond area.As a result of the implementation of the approved Action Plan, the concentrations oftritium detected in groundwater have generally been reduced to less than the LLD of200 pCi/L in the VB 2/3 and Pond area. As of December 2011 sampling, only sixmonitoring wells indicate tritium concentrations greater than 200 pCi/L, and nolocations indicate concentrations greater than 1,000 pCi/L. In addition, as of June 2012,only four small areas of residual tritium remain around the VB 2/3 and Pond area: threeisolated areas south of the Exelon Pond and a fourth area northwest of the Exelon Pond.Additionally, a significant amount of geologic and hydrogeologic data has beencollected as part of the Action Plan implementation, allowing for a better understanding of the groundwater movement and tritium migration.
Predictive modeling indicates that tritium will not migrate further off the Station's property at concentrations greaterthan the LLD even after all pumping activities have stopped.Documents which provide the foundation for the design and implementation ofremedial activities completed at the VB 2/3 and Pond area are presented in Section 6.0of this Plan Completion Report. Section 6.0 provides a list of references specific to theVB 2/3 and Pond area as well as pertinent documents related to the other areas on theBraidwood Station property where remediation of tritium in groundwater has beenperformed.
016841 (45)2CONEsToGA-ROVERS
& AssOCIATES 2.0 DESCRIPTION OF REMEDIATION This section describes the VB 2/3 and Pond area remediated, the remedial objectives required by the IEPA, and Exelon's implementation of the Action Plans to remediate groundwater in the VB 2/3 and Pond area.2.1 DESCRIPTION OF VB 2/3 AND POND AREALand surrounding the VB 2/3 and Pond area falls mainly into the agricultural, residential, and recreational use categories (Figure 2.1). Directly north of the VB 2/3area is the Exelon Pond. Further to the north, there are several ponds or small lakes.South of the VB 2/3 area is the Cooling Lake. The center of the Village of Braidwood isapproximately 7,200 feet from VB 2. To the northwest of the VB 2/3 area, there are twomain highways (Illinois State Highway 53 and Illinois Route 129) running parallel toeach other with a railroad (Southern Pacific Railroad) between them (Figure 2.2). VB 2 islocated approximately 3,000 feet east of VB 1 along the blowdown line, and VB 3 islocated approximately 600 feet northeast of VB 2.The VB 2/3 and Pond area includes the land and pond located at the northeast corner ofSmiley Road and Center Street (Figure 2.2). The pond is referred to as the "Exelon Pond"and covers approximately 30 acres (Figure 2.3). Figure 2.3 presents the monitoring wellnetwork in the vicinity of the VB 2/3 and Pond area. This figure includes temporary 1-inch diameter monitoring wells and permanent 2-inch diameter monitoring wells.Since late 2005, a total of 141 monitoring wells have been installed into the deep andshallow zones of the overburden sand aquifer in the VB 2/3 and Pond area.2.2 REMEDIAL OBJECTIVES The intent of the Action Plans was to address the groundwater that had been impactedby concentrations of tritium.
The first component was to prevent the migration oftritium at levels above 20,000 pCi/L from migrating off the Exelon owned property.
Thesecond component was to address those concentrations of tritium above 200 pCi/L, butbelow the drinking water standard of 20,000 pCi/L, in the VB 2/3 and Pond plume area.The following objectives were established as part of the Action Plans:016841 (45) 3 CONESTOGA-ROVERS
& ASSOCIATES 016841 (45)3CONEsToGA-ROVERS
& AsSOCIATES
* To restrict the migration of tritium in groundwater toward existing groundwater users, preventing levels above 20,000 pCi/L from migrating off Exelon ownedproperty* To reduce the amount of groundwater that is impaired by tritium at a concentration above 200 pCi/L but below the drinking water standard* To ensure that tritium migration does not potentially impact existing groundwater users and to prevent groundwater use of tritium-impacted groundwater 2.3 PRE-REMEDIATION CONDITIONS Active pumping of the Exelon Pond began in June 2006. Prior to the initiation of thispumping, comprehensive groundwater sampling was completed in January 2006.Figure 2.4 presents the groundwater elevations and flow directions in the deepoverburden sand aquifer for January 2006. This figure indicates that groundwater flowsgenerally northeast to north-northwest in this aquifer in the vicinity of VB 2/3 and theExelon Pond under natural (non-pumping) conditions.
The pattern of groundwater contours and the elevation of the water in the Exelon Pond indicate that there is asignificant interaction between the groundwater in the overburden sand aquifer and thewater in the Exelon Pond.Figure 2.5 presents the estimated horizontal distribution of tritium in the vicinity ofVB 2/3 in the deep zone of the overburden aquifer in January 2006. This figure indicates conditions prior to implementation of remedial activity.
2.4 ACTION PLAN IMPLEMENTATION
-GROUNDWATER PUMPINGTo accomplish the Action Plan objectives, as set out in the June 2006 Migration ControlPlan, Exelon initiated active remediation, which consisted of pumping water from theExelon Pond and from the recovery wells. By these activities, tritium-impacted groundwater is prevented from migrating and is eventually removed from thegroundwater aquifer.Pumping of the Exelon PondAs part of the Action Plan, pumping of the Exelon Pond began on June 11, 2006. Thepumping rate in the Exelon Pond was balanced to optimize the cleanup time whileminimizing potential effects on nearby private wells, ponds, and vegetation.
Drawdown016141 (45) 4 CONESTOGA-ROVERS
& ASSOCLATES 016841 (45)4CONESToGA-ROVERS
& AssocLATES of the Exelon Pond has been maintained at an elevation between 5 and 7 feet less thanthe elevation recorded in May 2006. Over 700,000,000 gallons of water have beenremoved from the Exelon Pond since pumping was initiated.
Water from the ExelonPond is pumped into the Braidwood Station blowdown line, which then empties into theKankakee River. The Exelon Pond is currently being pumped.In accordance with the Action Plan, groundwater monitoring of tritium concentrations and water levels has been performed at Exelon Pond on a quarterly basis. In addition, the capture of groundwater around the Exelon Pond is also evaluated quarterly with theuse of groundwater contour maps.Pumping of RW-9 and RW-1ORecovery wells (RW-9 and RW-10) were installed north of monitoring well BL-06 inNovember 2007. Both recovery wells are constructed of 8-inch diameter polyvinyl chloride (PVC) materials, with a 17-foot long PVC screen set at an approximate depth of27 feet below ground surface (bgs), at the top of the underlying confining layer (theWedron Formation).
Four-inch diameter submersible pumps were installed into each ofthe recovery wells.Pumping of these recovery wells began in January 2008. The groundwater captured bythese recovery wells is pumped directly into the Exelon Pond. The water in the ExelonPond is then pumped into the blowdown line at VB 2. These recovery wells werepumped at an average rate of 32 to 35 gallons per minute. Exelon stopped pumpingRW-9 and RW-10 in the spring of 2010. Currently, these recovery wells are notpumping.As part of Operations and Maintenance, groundwater monitoring of tritiumconcentrations and water levels has occurred on a quarterly basis. In addition, thecapture of groundwater around these recovery wells is also evaluated quarterly with theuse of groundwater contour maps.Monitoring of Private WellsPursuant to the Action Plan, 13 nearby private wells were monitored for tritium on aquarterly basis. Subsequently, this list was reduced to six private wells and two pondson five properties.
All private wells have indicated concentrations of tritium below theLLD since sampling was initiated in 2006. Appendix A provides the analytical data forthe private wells, and Figure 2.6 provides the private residential well locations that arecurrently sampled.016841 (45)5CONEsToGA-ROVERS
& AssocIATES 3.0 CURRENT GROUNDWATER CONDITIONS AT THE VB 2/3 AND POND AREAThis section presents the current groundwater conditions, an evaluation of the remedialaction, and an evaluation of future groundwater conditions at the VB 2/3 and Pondarea.3.1 CURRENT GROUNDWATER QUALITY CONDITIONS The concentrations of tritium in groundwater have been significantly reduced in theVB 2/3 and Pond area since the area has undergone active remediation.
The most recentgroundwater sampling event at each monitoring well location, as presented in Table 3.1,confirmed there are no instances of tritium in groundwater at concentrations above theUS EPA's drinking water standard of 20,000 pCi/L. More specifically, at the VB 2/3 andPond area, where pumping started in June of 2006, tritium concentrations have droppedfrom over 230,000 pCi/L to less than 1,000 pCi/L in June 2012. Furthermore, in the areanear RW-9 and RW-10, the concentrations of tritium in groundwater have been reducedby 100% at all monitoring well locations (e.g., BL-06, BL-06D, MW-140D, etc.).For the purposes of evaluation of the effectiveness of remediation, the VB 2/3 and Pondarea has been subdivided into specific areas, as defined on Figure 3.1. These specificareas include the VB 2 area (including the BL-06 and the RW-9 and RW-10 areas), theVB 3 area, the Exelon Pond area (further divided into the Northeast of Pond area, theNorthwest of Pond area, and the Southeast of Pond area), and the Leading Edge area.One of the tools used to evaluate groundwater conditions included a statistical analysisof each monitoring well that was sampled between January 2006 and June 2012.Appendix B presents the analytical results.
In some cases, data was available prior toJanuary 2006, in which case, the earlier data was also utilized.
Statistical analyses2include the trend, percent reduction, and minimum and maximum concentrations foreach monitoring well. Statistical analyses were only performed utilizing data frommonitoring locations that indicated tritium concentrations greater than the LLD duringat least one sampling event between January 2006 and June 2012. This included 21monitoring wells in the VB 2 area, five monitoring wells in the VB 3 area, 19 samplinglocations (including monitoring wells and the Exelon Pond) in the Exelon Pond area,and five monitoring wells in the Leading Edge area. Monitoring wells that did notindicate tritium concentrations greater than the LLD for at least one sampling eventbetween January 2006 and June 2012 were excluded from the statistical analysis.
The2 The trend was determined from the Mann-Kendall Trend Test. Percent reduction was calculated fromthe highest detected concentration and the most current concentration.
016841 (45)6CONEsToGA-ROVERS
& AsSOCLATES excluded monitoring wells included 21 monitoring wells in the VB 2 area, tenmonitoring wells in the VB 3 area, eight monitoring wells in the Exelon Pond area, andtwo monitoring wells in the Leading Edge area.The statistical analyses indicate a predominately downward trend of tritiumconcentrations in the groundwater monitoring wells in the vicinity of the VB 2/3 andPond area over time. Forty-three out of 49 monitoring well locations indicate areduction of tritium concentrations by 100%. In addition, all monitoring well locations indicate a reduction in tritium concentrations between the maximum detectedconcentration and the most recent concentration.
The following discussion outlines thestatistical analysis of each area in greater detail.VB 2 AreaTable 3.1 presents the latest tritium concentration detected in monitoring wells in theVB 2 area between December 2010 and December 2011. The statistical analyses indicatea predominately downward trend of tritium concentrations in the groundwater in thevicinity of VB 2. Tritium concentrations have been reduced by as much as 100%, from52,874 pCi/L in July 2006 to less than the LLD of 200 pCi/L in June 2012, as indicated atmonitoring well location BL-09D. Groundwater samples collected from monitoring wells in the VB 2 area are at levels less than the drinking water standard of 20,000 pCi/Land, in fact, all sample data, as of June 2012, are currently less than 318 pCi/L in theVB-2 area. Figures 3.2, 3.3, and 3.4 present this predominately downward trend intritium concentrations over time at select monitoring wells in the VB 2 area, BL-06 area,and RW-9 and RW-10 area, respectively.
VB 3 AreaTable 3.1 presents the latest tritium concentration detected in monitoring wells in theVB 3 area between December 2010 and December 2011. The statistical analyses indicatea predominately downward trend of tritium concentrations in the groundwater in thevicinity of VB 3. Tritium concentrations have been reduced by as much as 100%, from108,736 pCi/L in January 2006 to less than the LLD of 200 pCi/L in June 2012, asindicated at location VB-3-10D.
Groundwater samples collected from monitoring wellsin the VB 3 area are at levels significantly less than the drinking water standard of20,000 pCi/L, and, in fact, all sample data, as of June 2012, are currently less than249 pCi/L in the VB-3 area. Figure 3.5 presents this predominately downward trend intritium concentrations over time at select monitoring well locations in the VB 3 area.Exelon Pond AreaTable 3.1 presents the latest tritium concentration detected in monitoring wells in theExelon Pond area between December 2010 and December 2011. The statistical analyses016841 (45)7CONESTOGA-ROVERS
& ASSOCLATES indicated a predominately downward trend of tritium concentrations in thegroundwater near the Exelon Pond. Tritium concentrations have been reduced by asmuch as 100%, from 78,123 pCi/L in January 2007 to less than the LLD of 200 pCi/L inJune 2012, as indicated at location MW-135D.
Groundwater samples collected frommonitoring wells in the Exelon Pond area are at levels significantly less than thedrinking water standard of 20,000 pCi/L, and, in fact, all sample data, as of June 2012,are currently less than 1,000 pCi/L in the Exelon Pond area. 945 pCi/L (detected atmonitoring well P4D) was the highest tritium concentration detected in December 2011for the entire VB 2/3 and Pond area. Figures 3.6, 3.7, and 3.8 present the predominately downward trend in tritium concentrations over time at select monitoring wells in theNortheast of Pond area, the Northwest of Pond area, and the Southeast of Pond area,respectively.
Leading Edge AreaTable 3.1 presents the latest tritium concentration detected in monitoring wells in theLeading Edge area between December 2010 and December 2011. Tritium concentrations have been reduced by as much as 100%, from 969 pCi/L in September 2006 to less thanthe LLD of 200 pCi/L in June 2012, as indicated at location F-6D. Groundwater samplescollected from monitoring wells in the Leading Edge area are at levels significantly lessthan the drinking water standard of 20,000 pCi/L, and, in fact, all sample data arecurrently less than 529 pCi/L in the Leading Edge area. The statistical analyses indicatethat most monitoring wells in the vicinity of the Leading Edge have a downward trendof tritium concentrations in the groundwater.
Figure 3.9 graphically presents the tritiumconcentrations in the Leading Edge monitoring wells over time.3.2 CURRENT GROUNDWATER FLOW CONDITIONS Figure 3.10 provides the June 2012 groundwater contours for the VB 2/3 and Pond area.Since the shallow and deep monitoring wells are located within the same hydraulic unitand have historically indicated similar groundwater elevations, the shallow and deepmonitoring well elevations are contoured together.
Groundwater flow is generally tothe north. This figure also indicates the capture of groundwater around the ExelonPond due to the pumping of the Pond.016841 (45) 8 CONESTOGA-ROVERS
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& AssocLATES 3.3 COMPARISON OF CURRENTGROUNDWATER QUALITY CONDITIONS TO HISTORICAL DATAFigure 3.11 provides the June 2012 tritium concentrations and presents the isolated areasof residual tritium.
The areas of residual tritium in the VB 2/3 and Pond area have beensignificantly reduced since January 2006. Currently, there are four isolated areas ofdetectable
: tritium, three of which are directly south of the Exelon Pond and one to thenorthwest of the Exelon Pond. The isolated areas of detectable tritium which are locatedsouth of the Exelon Pond would be expected to flow into the Exelon Pond and beremediated by pumping or natural attenuation.
The isolated area of detectable tritiumto the northwest of the Exelon Pond would be expected to be remediated by naturalattenuation.
Figure 3.12 presents the January 2006 tritium plume versus the June 2012 residualtritium in the VB 2/3 and Pond area. This figure indicates a significant decrease intritium concentrations and impacted area since remedial activities began in June 2006.Tritium concentrations have been reduced from over 200,000 pCi/L to less than1,000 pCi/L. The January 2006 tritium plume has been reduced to four isolated areas ofresidual tritium in June 2012.3.4 EVALUATION OF THE REMEDIAL ACTIONThe remedial activities performed in the VB 2/3 and Pond area over the last 6 years havebeen very successful in decreasing the concentrations and reducing the extent of tritiumin groundwater.
During the course of pumping activities at the Exelon Pond and atRW-9 and RW-10, groundwater at select monitoring wells has been monitored on aquarterly basis for tritium concentrations and groundwater levels. The data collected over the last 6 years have been presented in Appendix B and on Figures 3.2 through 3.12.These data provide sufficient information to demonstrate the following regarding thecleanup of tritium in the VB 2/3 and Pond area:" There is no groundwater that contains tritium above the drinking water standard of20,000 pCi/L.* The current limits of detectable tritium (above 200 pCi/L) in this area have notextended beyond the Exelon owned property boundary.
" The maximum detected concentration in the entire area of VB 2/3 and the Pond as ofJune 2012 is 945 pCi/L.016841 (45) 9 CON ESTOGA-ROVERS
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* Only six out of 22 monitoring wells sampled during the June 2012 sampling eventindicated tritium concentrations above the LLD of 200 pCi/L.* The trend in tritium concentrations in routine sampling events has generally beendownward.
For 15 monitoring wells, either no trend could be statistically identified or there was not enough data available to determine a trend. One monitoring wellindicated an upward trend; however, this location indicated tritium concentrations below the LLD for the last four sampling events.* Since June 2006, the cone of influence (capture zone) around the Exelon Pond hasbeen successful in preventing further migration of tritium from this area.* Since January 2008, pumping and the resultant cone of influence (capture zone)around the two recovery wells (RW-9 and RW-10) have been successful inpreventing further migration of tritium from the area around BL-06.3.5 EVALUATION OF FUTURE GROUNDWATER CONDITIONS Predictive modeling simulations were performed in 2012 in order to determine the effectof a complete shutdown of all pumping activities (Exelon Pond and RW-9 and RW-10) inthe VB 2/3 and Pond area on tritium extent and concentrations.
Modeling ofgroundwater and tritium in this area indicates that the residual areas of detectable tritium located south of the Exelon Pond will dissipate within 0.3 year (120days).
Theareas of residual tritium to the northwest of the Exelon Pond will dissipate to aconcentration below the LLD of 200 pCi/L within 0.4 years (150 days). The isolatedareas of residual tritium in groundwater will not migrate off the Station's licensedproperty or onto private property at levels above the LLD of 200 pCi/L.Exelon initiated active pumping of groundwater based on the results from the predictive groundwater flow and transport modeling (CRA, August 2006, 2008). Pumping fromthe Exelon Pond directly with accelerated extractions (using extraction wells) in the areasouth of Exelon Pond was considered the most efficient remedial option to clean up thetritium plume associated with the releases from Vacuum Breakers 2 and 3. Thispumping operation has been ongoing since June 2006. Routine quarterly groundwater monitoring data from 2006 to 2012 have demonstrated that the tritium plume has beenshrinking over time to the current measured conditions.
It is anticipated that the remaining isolated areas of detectable tritium in groundwater will attenuate naturally over time, even if all pumping activities are stopped (both fromExelon Pond and from extraction wells RW-9 and RW-10). In order to verify that these018841 (45) 10 CONESTOGA-ROVERS
& ASSOCIATES 016841 (45)10CONESTOGA-ROVERS
& Assoc[ATES residual areas of tritium in groundwater would naturally attenuate in the future withoutpumping, additional groundwater flow and transport modeling was performed usingJune 2012 data. The primary objective of these modeling efforts was to evaluate howlong it will take for the areas of residual tritium to dissipate (i.e., with tritiumconcentrations reduced to below the LLD of 200 pCi/L). The second objective of themodeling was to determine the migration pathway of the residual tritium.
Thememorandum presenting this groundwater flow and transport modeling effort isprovided in Appendix C.The modeling results demonstrate that the extent of the residual tritium areas willdecrease while the areas may migrate slightly further downgradient from the currentlocation.
The areas of residual tritium will eventually reduce to below the LLD of200 pCi/L within 150 days after the pumping cessation.
In addition, tritiumconcentrations will increase initially and then drop sharply to below the LLD(200 pCi/L).The following conclusions can be drawn based on the groundwater modelingsimulations:
* It will take less than 150 days for the isolated areas of residual tritium ingroundwater in the VB 2/3 and Pond area to naturally attenuate to below the LLD of200 pCi/L after the current pumping operations at the Exelon Pond and theextraction wells are stopped; and* The isolated areas of residual tritium in groundwater will not migrate onto otheradjacent private properties after the pumping operations are shut down.016841 (45) 11 CONESTOGA-ROVERS
& ASSOCIATES 016841 (45)11CONESTOGA-ROVERS
& ASSOCIATES
==4.0 CONCLUSION==
S The remedial activities in the VB 2/3 and Pond area have resulted in a significant decrease in tritium concentrations and reduction in the overall extent of tritium ingroundwater.
This reduction has occurred in the last 6 years through active pumpingand by the natural attenuation of tritium in the groundwater.
This Plan Completion Report documents the effectiveness of the remedial activities todate, as well as the ability of natural attenuation to eliminate the remaining isolatedareas of residual tritium.
Specifically, the following conclusions have been reached withregard to the remedial actions at the VB 2/3 and Pond area:* Concentrations of tritium in groundwater are less than the drinking water standardof 20,000 pCi/L." As of June 2012, tritium concentrations in groundwater have decreased to less than1,000 pCi/L and only four small isolated areas of residual tritium remain in the VB2/3 and Pond area.* Localized areas of residual concentrations of tritium above 200 pCi/L will notmigrate off the Station's licensed property or Exelon owned property, and will notimpact other off-Site private groundwater users.016841 (45) 12 CONEsToGA-ROvERS
& ASSOCIATES 016841(45) 12CONEsToGA-ROVERS
& AssocIATES 5.0 PLANNED COMPLETION ACTIVITIES As a final component of the remedial strategy at the VB 2/3 and Pond area, thegroundwater pumping activities will be shut down. In addition, the current quarterly groundwater monitoring program will be discontinued.
: However, as part of the nuclearpower industry's voluntary groundwater monitoring
: programs, Exelon will continuegroundwater monitoring of a number of key monitoring wells in the VB 2/3 and Pondarea. The monitoring wells that were associated with the quarterly groundwater monitoring program will be abandoned.
Each of these aspects is presented in moredetail below.Shutdown of Pumping Activities Exelon will terminate the pumping in the Exelon Pond and in recovery wells RW-9 andRW-10, and dismantle the equipment.
Upon shutdown of the pumping systems, thewater level in Exelon Pond is expected to recover upward to conditions prior topumping (i.e., similar to the surrounding static groundwater elevations).
It isanticipated that Exelon will restore the land surface and vegetation in the areas of thepumping equipment and discharge lines to at least the same conditions as prior toremedial activities.
Groundwater Monitoring ProgramWhile the current monitoring program will be discontinued, the VB 2/3 and Pond areawill continue to be monitored through Exelon's Radioactive Groundwater Protection Program (RGPP)3.
The RGPP is a program that meets the guidance provided by NEI07-07, ANI 07-01, and EPRI 1015118.
VB 2/3 and Pond area monitoring wells includedin the RGPP are presented in Table 5.1 and on Figure 5.1. The goal of the RGPPmonitoring is to ensure that any potential future impacts to groundwater are identified by Exelon in a timely manner.Monitoring Well Abandonment Monitoring wells in the VB 2/3 and Pond area that are not associated with the RGPPwill be abandoned and sealed. The monitoring wells to be abandoned and sealed arelisted in Table 5.2. Monitoring wells designated BL are considered blowdown linemonitoring well locations and will not be abandoned.
3 Monitoring wells that are currently above 200 pCi/L, but not included in the RGPP, will be monitored during RGPP sampling events. These monitoring wells will continue to be monitored until twoconsecutive sampling events indicate tritium concentrations below 200 pCi/L, at which time themonitoring well will be abandoned.
This includes VB-2-5D, VB-3-4D, P-4D, and P-13D.016841 (45)13CONESTOGA-ROVERS
& ASSOCIATES
==6.0 REFERENCES==
CRA, March 2006. Tritium Investigation, Exelon Generation, Braidwood Station,Braceville, Illinois.
CRA, April 2006. Investigation of Tritium in Groundwater in the Vicinity of VacuumBreakers 2 and 3, Braidwood
: Station, Braceville, Illinois.
CRA, May 2006. Agreed Preliminary Injunction Order.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. Hydraulic Monitoring for the Will County Forest Preserve WorkPlan Braidwood Generating Station Braceville, Illinois.
CRA, November 2006. Minimize Impairment Plan for Vacuum Breakers 2 and 3Braidwood Generation, Station Braceville, Illinois.
CRA, December 2006. CRA Memorandum, Transient Groundwater Flow ModelCalibration and Transport Model Scenario Update.CRA, January 2007. Wedron Clay Till Investigation Report Braidwood Generating
: Station, Braceville, Illinois.
CRA, January 2008. Simulation of Aggressive Remedial Option (VB-2 and 3), ExelonGeneration
: Company, LLC Braidwood
: Station, Braceville, Illinois.
: 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 toModularization Concepts and the Ground-Water Flow Process, United StatesGeological Survey Open-File Report 00-92, Reston, Virginia.
: 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 96-486, Reston, Virginia.
016841 (45)14CONESTOGA-ROVERS
& Assoc[ATES
: McDonald, M.G. and A.W. Harbaugh, 1988. A Modular Three-Dimensional Finite-Difference Ground-Water Flow Model, United States Geological SurveyOpen-File Report 83-875.Pollock, D.W., 1994. User's Guide for MODPATH/MODPATH-PLOT, Version 3: Aparticle tracking post-processing package for MODFLOW, the U.S. Geological Survey finite-difference ground-water flow model: U.S. Geological SurveyOpen-File Report 94464.Rumbaugh, J.O and J.B Rumbaugh, 2011. Guide to Using Groundwater Vistas,Version 6, Environmental Simulations Inc., Herndon, Virginia.
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, andChemical Reactions of Contaminants in Groundwater Systems; Documentation and User's Guide. Prepared by University of Alabama, Prepared for US ArmyCorps of Engineers.
0i684i (45) 15 CONESTOGA-ROVERS
& ASSOCIATES 016841 (45)15CONESToGA-ROVERS
& AssocIATES 7-41000 20000LEGENDva-1 A VACUUM BREAKER LOCATIONi
~wANDBLWOW DOWN LINE7 '4 ittfigure 2.1VB 2/3 AND POND AREA SITE LOCATION MAPEXELON GENERATION BRAIDWOOD STATIONBraceville, Illinois0 CD//N-,j7241000 200M* ---APPROXIMATE BLOWOOWN PROPERTY UNEBLOWDOWNL UNEMAKEUP UNEVB-i A VACUUM BREAKERBL-li f') MID POINT MONITORING WELL LOCATION AND IDENTFIER VB-I-l & VACUUM BREAKER MONITORING WELL LOCATION AND IDENTIFIER figure 2.2LOCATION MAP FOR VB 2/3 AND POND AREAEXELON GENERATION BRAIDWOOD STATIONBrace vlle, Illinois LEGENDET FENCE UNESLOWDOWN LINEAPPROXIMATE PROPERTY BOUNDARYSLOWDOWN PROPERTY BOUNDARYSHALLOW SLOWDOWN LINE SAMPLING LOCATION,(A~ CELL84 0PAD00.T" m-o~uDEEP SLOWDOWN LINE SAMPLING LOCATIONVACUUM BREAKER LOCATIONPRIVATE WELUSURFACE WATER LOCATIONSHALLOW TEMPORARY WELL LOCATIONDEEP TEMPORARY WELL LOCATIONRECOVERY WELL LOCATIONPERMANENT MONITORING WELL LOCATIONSTAFF GAUGE LOCATIONIMW~NOTE-ONLY PRIVATE WELL LOCATIONS THAT ARECURRENTLY SAMPLED BY EXELON ARE SHOWN-ONLY MONITORING WELLS WITH DATA PROVIDED IN THISREPORT ARE PRESENTED ON THIS FIGUREVS-3-7Dova_,-,=2 figure 2.3MONITORING WELL AND PRIVATE WELL LOCATIONS VB 2/3 AND POND AREAEXELON GENERATION BRAIDWOOD STATIONBraceOvi/e,
///inois (58T00)~ © PW-13(58 7258588.!2 .........
589C ~ ~ -_0-* ......... .7Dfr(VB-2-3t VB,-2-0 VB-3-7D(590.88)
(590.17)
." 51 25) (581,59)VB-3-100
)B*#VB-2-7D (591.37)(591,02) 2L-2L) V " S-3(591.12)
(591 47)8L~ ~ 0 3 589 2-6L ) 1.35) XD ki ,10 20O 400ftCE UNE PW.a PRIVATE WELL LOCATIONLEGENDEXMTING PENVR-3 Avw 1 ,,;1" InPLANT PROPERTY UNE (2006)BLOWDOWN UNE SAMPUNG LOCATIONVACUUM BREAKER LOCATIONVACUUM BREAKER SAMPUNG LOCATIONMONITORING WELL LOCATIONSTAFF GAUGE LOCATION591 WELL. LOCATION~
RECOVERY WELL LOCATIONGROUNDWATER ELEVATION (ft AMSL)GROUNDWATER ELEVATION CONTOUR (It ASIL)GROUNDWATER FLOW DIRECTION MONITORM WELLDATATAKEN JANUARY&
2MOTO JANUARY 24.2Wlfigure 2.4GROUNDWATER LEVEL CONTOURS
-JANUARY 2006DEEP GROUNDWATER ZONEEXELON GENERATION BRAIDWOOD STATIONBrace wle, Illinois NIW9.3APAD 0RW.2 0-200-EXISTING FENCE UNEEXISTING PERIMETER DITCH UMITSBLOWDOWN UINEPLANT PROPERTY UNE (200M)DEEP SLOWDOWN UNE SAMPLING LOCATIONVACUUM BREAKER LOCATIONDEEP VACUUM BREAKER SAMPLING LOCATIONDEEP MONITORING WELL LOCATIONPRIVATE WELL LOCATIONDEEP TEMPORARY WELL LOCATION BACKGODRINIGNPOND SAMPLING LOCATION TRITIUMJANUAR)DEEP RECOVERY WELL LOCATION USING LCTRITIUM RESULT IN GROUNDWATER TRITIUM CONTOURSOURCE: CPA MARCH 2006 TRITIUM INVESTIGATION TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIESIUTER)
TRITIUM RESULTS 100,000 TO 200,000TRITIUM RESULTS 60,000 TO 100,000TRITIUM RESULTS 40.000 TO 60M0OWTRITIUM RESULTS 20,000 TO 40,000TRITIUM RESULTS 10,000 TO 20.000TRITIUM RESULTS 5,000 TO 10.000TRITIUM RESULTS 200 TO 5.000TRITIUM RESULTS 0 TO 200(ND) NONDETECT BELOW 200 pCItLDUND TRITIUM CONCENTRATION:
200 PCIJL3 WATER STANDARD FOR TRITIUM:
20,000 PCULDATA FOR SAMPLES COLLECTED THROUGH30,o2006.
CONTOURS WEE figure 2.5OG VALUES.ESTIMATED TRITIUM RESULTS-JANUARY 2006DEEP GROUNDWATER ZONEEXELON GENERATION BRAIDWOOD STATIONBrace//le,
///inoisAMA ..... 10841r75I045)N-4=1h
-n 1-1.V 0}}

Revision as of 23:47, 2 July 2018

Plan Completion Report for the VB 2/3 and Pond Area
ML14030A285
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Site: Braidwood  Constellation icon.png
Issue date: 12/31/2012
From:
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To:
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Text

PLAN COMPLETION REPORT FOR THE VB 2/3 ANDPOND AREABRAIDWOOD GENERATION STATIONBRACEVILLE, ILLINOISPrepared For:Exelon Generation

Company, LLCDISCLAIMER:

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

Prepared by:Conestoga-Rovers

& Associates 8615 West Bryn MawrChicago, Illinois 60631DECEMBER 2012REF. NO. 016841 (45)This report is printed on recycled paper.Office: (773) 380-9933Fax: (773) 380-6421web: http:\\www.CRAworld.com 4TABLE OF CONTENTSPage

1.0 INTRODUCTION

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

12.0 DESCRIPTION OF REMEDIATION

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

32.1 DESCRIPTION OF VB 2/3 AND POND AREA ..........................................

32.2 REM EDIAL OBJECTIVES

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

32.3 PRE-REMEDIATION CONDITIONS

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

42.4 ACTION PLAN IMPLEMENTATION

-GROUNDWATER PUMPING .... 43.0 CURRENT GROUNDWATER CONDITIONS AT THE VB 2/3 AND POND AREA... 63.1 CURRENT GROUNDWATER QUALITY CONDITIONS

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

63.2 CURRENT GROUNDWATER FLOW CONDITIONS

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

83.3 COMPARISON OF CURRENTGROUNDWATER QUALITY CONDITIONS TO HISTORICAL DATA ..... 93.4 EVALUATION OF THE REMEDIAL ACTION ...................

93.5 EVALUATION OF FUTURE GROUNDWATER CONDITIONS

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

104.0 CO N CLU SIO N S .....................................................................................................................

125.0 PLANNED COMPLETION ACTIVITIES

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

136.0 REFEREN CES .........................................................................................................................

14016841 (45) CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)CONESTOGA-ROVERS

& Assoc[ATES LIST OF FIGURESFIGURE 2.1FIGURE 2.2FIGURE 2.3FIGURE 2.4FIGURE 2.5FIGURE 2.6FIGURE 3.1FIGURE 3.2FIGURE 3.3FIGURE 3.4FIGURE 3.5FIGURE 3.6FIGURE 3.7FIGURE 3.8FIGURE 3.9FIGURE 3.10VB 2/3 AND POND AREA SITE LOCATION MAPLOCATION MAP FOR VB 2/3 AND POND AREAMONITORING WELL AND PRIVATE WELL LOCATIONS

-VB 2/3 ANDPOND AREAGROUNDWATER LEVEL CONTOURS

-JANUARY 2006 -DEEPGROUNDWATER ZONEESTIMATED TRITIUM RESULTS -JANUARY 2006 -DEEPGROUNDWATER ZONECURRENT RESIDENTIAL SAMPLING LOCATIONS INDEX OF VB 2/3 AND EXELON POND AREA LOCATIONS TRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THEVB 2 AREATRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THEBL-06 AREATRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THERW-9 AND RW-10 AREATRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THEVB 3 AREATRITIUM CONCENTRATION TRENDS IN MONITORING WELLSNORTHEAST OF PONDTRITIUM CONCENTRATION TRENDS IN MONITORING WELLSNORTHWEST OF PONDTRITIUM CONCENTRATION TRENDS IN MONITORING WELLSSOUTHEAST OF PONDTRITIUM CONCENTRATION TRENDS IN MONITORING WELLS AT THELEADING EDGEGROUNDWATER CONTOURS

-JUNE 2012016841 (48) CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)CONESTOGA-ROVERS

& Assoc[ATES LIST OF FIGURES0FIGURE 3.11FIGURE 3.12FIGURE 5.1CONCENTRATION OF TRITIUM IN GROUNDWATER

-JUNE 2012JANUARY 2006 TRITIUM PLUME VS JUNE 2012 RESIDUAL TRITIUMRGPP MONITORING WELL LOCATIONS IN THE VB 2/3 AND PONDAREA016841 (45) CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)CONEsToGA-ROVERS

& AsSOCIATES LIST OF TABLESTABLE 3.1TABLE 5.1TABLE 5.2SUMMARY OF RECENT TRITIUM ANALYSIS IN MONITORING WELLSNEAR VB 2/3 AND POND AREASUMMARY OF CURRENT RGPP MONITORING WELLS IN THE VB 2/3AND POND AREASUMMARY OF MONITORING WELLS TO BE ABANDONED 016841 (45) CONESTOGA-ROVERS

& ASSOCIATES 016841(45)

CONEsToGA-ROVERS

& AssoclATES LIST OF APPENDICES APPENDIX AAPPENDIX BAPPENDIX CSUMMARY OF TRITIUM ANALYSIS AT PRIVATE WELLS AND PONDSSUMMARY OF TRITIUM ANALYSES IN MONITORING WELLS NEARVB 2, VB 3, THE EXELON POND AND THE LEADING EDGE AREASGROUNDWATER MODELING RESULTS (Memorandum) 016841 (45) CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)CONEsToGA-ROVERS

& Assoc[ATES EXECUTIVE SUMMARYThis document demonstrates the successful completion of the remediation of tritium inshallow groundwater at the Exelon Generation Company LLC's (Exelon)

Braidwood Generating Station property (Station) in Braceville, Illinois 1, specifically in the VacuumBreaker 2/3 and Pond (VB 2/3 and Pond) area. Groundwater which had previously been impacted by tritium released from the Station's Blowdown Line has been cleanedup to safe levels through the use of active pumping and monitored natural attenuation.

In accordance with the March 11, 2010 Agreed Consent Order, this document presentsthe Plan Completion Report for the VB 2/3 and Pond Area. This Plan Completion Report fully describes the implementation, identifies any corrective action goals thathave been met, and demonstrates the efficacy of the remedy as implemented.

In late 2005 and early 2006, surface water and groundwater investigations led to thediscovery of elevated tritium concentrations in the groundwater in the VB 2/3 and Pondarea. The elevated tritium concentrations in the groundwater were attributed to leaks inthe vacuum breaker valves. The leaks were subsequently repaired.

In order toremediate the groundwater in the VB 2/3 and Pond area, Exelon initiated activeremediation through the pumping of the Exelon Pond in June 2006 and the pumping ofrecovery wells RW-9 and RW-10 in January 2008.Through active remediation, tritium concentrations in groundwater in this area havedecreased significantly between January 2006 and June 2012. Tritium concentrations inJanuary 2006 were as high as 228,283 picocuries per liter (pCi/L) (at monitoring wellP-13D), while in June 2012, the maximum tritium concentration detected was 945 pCi/L(at monitoring well P-4D). The active remediation significantly decreased tritiumconcentrations in the groundwater to below the drinking water standard (20,000 pCi/L)and has prevented further migration of tritium in groundwater off Exelon-owned property at concentrations greater than the lower limit of detection (LLD) of 200 pCi/L.The data, evaluations, and modeling contained in this Plan Completion Report lead tothe following conclusions which support the closure of all remedial activities at theVB 2/3 and Pond area.'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 byExelon along Smiley Road and Center Street.016841(45)

CONEsToGA-ROVERS

& AssocIATES

  • The maximum concentrations of residual tritium in groundwater in the VB 2/3 andPond area as of June 2012 are less than 5% of the US EPA's drinking water standardof 20,000 pCi/L; and" As demonstrated by predictive
modeling, the residual levels of tritium in theVB 2/3 and Pond area will not migrate further off the Station's licensed propertyand onto private property at levels above the LLD of 200 pCi/L.016841 (45) ii CONESTOGA-ROVERS

& AssociATEs 016841 (45)HiCONEsToGA-ROVERS

& AsSOCIATES

1.0 INTRODUCTION

AND PURPOSEThis Plan Completion Report has been prepared for the Illinois Environmental Protection Agency (IEPA) to address groundwater remediation regarding the VacuumBreaker 2/3 and related Pond area at the Exelon Generation Company LLC's (Exelon)Braidwood Generating Station property located in Braceville, Illinois.

Specifically, thisReport discusses the groundwater investigation, monitoring, and remedial actions thatwere implemented in accordance with the Agreed Preliminary Injunction Order (PIO)dated May 24, 2006, and the March 11, 2010 Agreed Consent Order (ACO), entered intoby Exelon and the State of Illinois.

Information collected to date as a result of ActionPlan implementation is sufficient to determine that remediation at the VB 2/3 andExelon Pond area is complete and can be concluded.

These orders refer to a number of "Action Plans" necessary to remediate groundwater impacted by tritium to levels below the drinking water standard

[20,000 picocuries perliter (pCi/L)]

and then to levels below agreed upon background levels (200 pCi/L)which is represented by the lower limit of detection (LLD).The first Action Plan generated for the VB 2/3 and Pond Area was the June, 2006"Migration Control Plan, Vacuum Breakers 2 and 3". This plan involved the pumping ofthe Exelon Pond and the prevention of tritium migrating off of Exelon's property atlevels above the drinking water standard (20,000 pCi/L). The second Action Plandeveloped for the VB 2/3 and Pond Area was the November 2006 "Minimize Impairment Plan for Vacuum Breakers 2 and 3". This (Minimize Impairment) plan was to beimplemented if tritium remained for a significant time period at concentrations belowthe drinking water standard, but above the LLD at locations off the Exelon Property.

This plan has not been implemented as the remedial efforts have been successful insignificantly reducing tritium in groundwater.

Current modeling (Section 3.5) indicates that any residual tritium remaining in groundwater will be mitigated by naturalattenuation to concentrations below the LLD of 200 pCi/L before it migrates from itsexisting location to adjacent properties.

This Report presents the data gathered to demonstrate that the remedial efforts in theVB 2/3 and Pond area have been successful and that all required objectives provided inthe Action Plans of the PIO and ACO have been met. All tritium concentrations arecurrently below 1,000 pCi/L, and future predictive modeling indicates that tritium willnot migrate further off the Station's property at concentrations greater than the LLD of200 pCi/L, even after all pumping activities have stopped.

As such, remediation isconsidered complete for this area.016841 (45)ICONESTOGA-ROVERS

& ASSOCIATES The PIO and ACO were put into place as a result of several tritium leaks detected byExelon. In 1998 and 2000, leaks originating from the vacuum breakers were detectedand subsequently repaired.

In the spring of 2005, following the detection of tritiumabove ambient levels in the perimeter ditch, Exelon investigated shallow groundwater on the east side of the Station, in areas along Smiley Road and Center Street, and alongthe Station's blowdown line. As a result of these investigations, the vacuum breakerswere repaired and active remediation in the VB 2/3 and Pond area was initiated.

Aspresented in the June 2006 Migration Control Plan, the remediation in the VB 2/3 andPond area included pumping of the Exelon Pond. The pumping of the Exelon Pond wasinitiated in June 11, 2006. In January 2007, elevated tritium concentrations were detectedin the area near monitoring well BL-06 (south of the pond). Exelon installed tworecovery wells (RW-9 and RW-10) north of BL-06 in November 2007. RW-9 and RW-10began pumping in January 2008. Since 2006, Exelon has developed an extensive monitoring well network in the VB 2/3 and Pond area in order to monitor tritiumconcentrations.

Select monitoring wells are monitored on a quarterly basis for tritiumconcentrations and for water levels.Since the initiation of these remedial activities, Exelon has pumped over 700,000,000 gallons of water from the Exelon Pond in support of its remedial activities at theVB 2/3 and Pond area.As a result of the implementation of the approved Action Plan, the concentrations oftritium detected in groundwater have generally been reduced to less than the LLD of200 pCi/L in the VB 2/3 and Pond area. As of December 2011 sampling, only sixmonitoring wells indicate tritium concentrations greater than 200 pCi/L, and nolocations indicate concentrations greater than 1,000 pCi/L. In addition, as of June 2012,only four small areas of residual tritium remain around the VB 2/3 and Pond area: threeisolated areas south of the Exelon Pond and a fourth area northwest of the Exelon Pond.Additionally, a significant amount of geologic and hydrogeologic data has beencollected as part of the Action Plan implementation, allowing for a better understanding of the groundwater movement and tritium migration.

Predictive modeling indicates that tritium will not migrate further off the Station's property at concentrations greaterthan the LLD even after all pumping activities have stopped.Documents which provide the foundation for the design and implementation ofremedial activities completed at the VB 2/3 and Pond area are presented in Section 6.0of this Plan Completion Report. Section 6.0 provides a list of references specific to theVB 2/3 and Pond area as well as pertinent documents related to the other areas on theBraidwood Station property where remediation of tritium in groundwater has beenperformed.

016841 (45)2CONEsToGA-ROVERS

& AssOCIATES 2.0 DESCRIPTION OF REMEDIATION This section describes the VB 2/3 and Pond area remediated, the remedial objectives required by the IEPA, and Exelon's implementation of the Action Plans to remediate groundwater in the VB 2/3 and Pond area.2.1 DESCRIPTION OF VB 2/3 AND POND AREALand surrounding the VB 2/3 and Pond area falls mainly into the agricultural, residential, and recreational use categories (Figure 2.1). Directly north of the VB 2/3area is the Exelon Pond. Further to the north, there are several ponds or small lakes.South of the VB 2/3 area is the Cooling Lake. The center of the Village of Braidwood isapproximately 7,200 feet from VB 2. To the northwest of the VB 2/3 area, there are twomain highways (Illinois State Highway 53 and Illinois Route 129) running parallel toeach other with a railroad (Southern Pacific Railroad) between them (Figure 2.2). VB 2 islocated approximately 3,000 feet east of VB 1 along the blowdown line, and VB 3 islocated approximately 600 feet northeast of VB 2.The VB 2/3 and Pond area includes the land and pond located at the northeast corner ofSmiley Road and Center Street (Figure 2.2). The pond is referred to as the "Exelon Pond"and covers approximately 30 acres (Figure 2.3). Figure 2.3 presents the monitoring wellnetwork in the vicinity of the VB 2/3 and Pond area. This figure includes temporary 1-inch diameter monitoring wells and permanent 2-inch diameter monitoring wells.Since late 2005, a total of 141 monitoring wells have been installed into the deep andshallow zones of the overburden sand aquifer in the VB 2/3 and Pond area.2.2 REMEDIAL OBJECTIVES The intent of the Action Plans was to address the groundwater that had been impactedby concentrations of tritium.

The first component was to prevent the migration oftritium at levels above 20,000 pCi/L from migrating off the Exelon owned property.

Thesecond component was to address those concentrations of tritium above 200 pCi/L, butbelow the drinking water standard of 20,000 pCi/L, in the VB 2/3 and Pond plume area.The following objectives were established as part of the Action Plans:016841 (45) 3 CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)3CONEsToGA-ROVERS

& AsSOCIATES

  • To restrict the migration of tritium in groundwater toward existing groundwater users, preventing levels above 20,000 pCi/L from migrating off Exelon ownedproperty* To reduce the amount of groundwater that is impaired by tritium at a concentration above 200 pCi/L but below the drinking water standard* To ensure that tritium migration does not potentially impact existing groundwater users and to prevent groundwater use of tritium-impacted groundwater 2.3 PRE-REMEDIATION CONDITIONS Active pumping of the Exelon Pond began in June 2006. Prior to the initiation of thispumping, comprehensive groundwater sampling was completed in January 2006.Figure 2.4 presents the groundwater elevations and flow directions in the deepoverburden sand aquifer for January 2006. This figure indicates that groundwater flowsgenerally northeast to north-northwest in this aquifer in the vicinity of VB 2/3 and theExelon Pond under natural (non-pumping) conditions.

The pattern of groundwater contours and the elevation of the water in the Exelon Pond indicate that there is asignificant interaction between the groundwater in the overburden sand aquifer and thewater in the Exelon Pond.Figure 2.5 presents the estimated horizontal distribution of tritium in the vicinity ofVB 2/3 in the deep zone of the overburden aquifer in January 2006. This figure indicates conditions prior to implementation of remedial activity.

2.4 ACTION PLAN IMPLEMENTATION

-GROUNDWATER PUMPINGTo accomplish the Action Plan objectives, as set out in the June 2006 Migration ControlPlan, Exelon initiated active remediation, which consisted of pumping water from theExelon Pond and from the recovery wells. By these activities, tritium-impacted groundwater is prevented from migrating and is eventually removed from thegroundwater aquifer.Pumping of the Exelon PondAs part of the Action Plan, pumping of the Exelon Pond began on June 11, 2006. Thepumping rate in the Exelon Pond was balanced to optimize the cleanup time whileminimizing potential effects on nearby private wells, ponds, and vegetation.

Drawdown016141 (45) 4 CONESTOGA-ROVERS

& ASSOCLATES 016841 (45)4CONESToGA-ROVERS

& AssocLATES of the Exelon Pond has been maintained at an elevation between 5 and 7 feet less thanthe elevation recorded in May 2006. Over 700,000,000 gallons of water have beenremoved from the Exelon Pond since pumping was initiated.

Water from the ExelonPond is pumped into the Braidwood Station blowdown line, which then empties into theKankakee River. The Exelon Pond is currently being pumped.In accordance with the Action Plan, groundwater monitoring of tritium concentrations and water levels has been performed at Exelon Pond on a quarterly basis. In addition, the capture of groundwater around the Exelon Pond is also evaluated quarterly with theuse of groundwater contour maps.Pumping of RW-9 and RW-1ORecovery wells (RW-9 and RW-10) were installed north of monitoring well BL-06 inNovember 2007. Both recovery wells are constructed of 8-inch diameter polyvinyl chloride (PVC) materials, with a 17-foot long PVC screen set at an approximate depth of27 feet below ground surface (bgs), at the top of the underlying confining layer (theWedron Formation).

Four-inch diameter submersible pumps were installed into each ofthe recovery wells.Pumping of these recovery wells began in January 2008. The groundwater captured bythese recovery wells is pumped directly into the Exelon Pond. The water in the ExelonPond is then pumped into the blowdown line at VB 2. These recovery wells werepumped at an average rate of 32 to 35 gallons per minute. Exelon stopped pumpingRW-9 and RW-10 in the spring of 2010. Currently, these recovery wells are notpumping.As part of Operations and Maintenance, groundwater monitoring of tritiumconcentrations and water levels has occurred on a quarterly basis. In addition, thecapture of groundwater around these recovery wells is also evaluated quarterly with theuse of groundwater contour maps.Monitoring of Private WellsPursuant to the Action Plan, 13 nearby private wells were monitored for tritium on aquarterly basis. Subsequently, this list was reduced to six private wells and two pondson five properties.

All private wells have indicated concentrations of tritium below theLLD since sampling was initiated in 2006. Appendix A provides the analytical data forthe private wells, and Figure 2.6 provides the private residential well locations that arecurrently sampled.016841 (45)5CONEsToGA-ROVERS

& AssocIATES 3.0 CURRENT GROUNDWATER CONDITIONS AT THE VB 2/3 AND POND AREAThis section presents the current groundwater conditions, an evaluation of the remedialaction, and an evaluation of future groundwater conditions at the VB 2/3 and Pondarea.3.1 CURRENT GROUNDWATER QUALITY CONDITIONS The concentrations of tritium in groundwater have been significantly reduced in theVB 2/3 and Pond area since the area has undergone active remediation.

The most recentgroundwater sampling event at each monitoring well location, as presented in Table 3.1,confirmed there are no instances of tritium in groundwater at concentrations above theUS EPA's drinking water standard of 20,000 pCi/L. More specifically, at the VB 2/3 andPond area, where pumping started in June of 2006, tritium concentrations have droppedfrom over 230,000 pCi/L to less than 1,000 pCi/L in June 2012. Furthermore, in the areanear RW-9 and RW-10, the concentrations of tritium in groundwater have been reducedby 100% at all monitoring well locations (e.g., BL-06, BL-06D, MW-140D, etc.).For the purposes of evaluation of the effectiveness of remediation, the VB 2/3 and Pondarea has been subdivided into specific areas, as defined on Figure 3.1. These specificareas include the VB 2 area (including the BL-06 and the RW-9 and RW-10 areas), theVB 3 area, the Exelon Pond area (further divided into the Northeast of Pond area, theNorthwest of Pond area, and the Southeast of Pond area), and the Leading Edge area.One of the tools used to evaluate groundwater conditions included a statistical analysisof each monitoring well that was sampled between January 2006 and June 2012.Appendix B presents the analytical results.

In some cases, data was available prior toJanuary 2006, in which case, the earlier data was also utilized.

Statistical analyses2include the trend, percent reduction, and minimum and maximum concentrations foreach monitoring well. Statistical analyses were only performed utilizing data frommonitoring locations that indicated tritium concentrations greater than the LLD duringat least one sampling event between January 2006 and June 2012. This included 21monitoring wells in the VB 2 area, five monitoring wells in the VB 3 area, 19 samplinglocations (including monitoring wells and the Exelon Pond) in the Exelon Pond area,and five monitoring wells in the Leading Edge area. Monitoring wells that did notindicate tritium concentrations greater than the LLD for at least one sampling eventbetween January 2006 and June 2012 were excluded from the statistical analysis.

The2 The trend was determined from the Mann-Kendall Trend Test. Percent reduction was calculated fromthe highest detected concentration and the most current concentration.

016841 (45)6CONEsToGA-ROVERS

& AsSOCLATES excluded monitoring wells included 21 monitoring wells in the VB 2 area, tenmonitoring wells in the VB 3 area, eight monitoring wells in the Exelon Pond area, andtwo monitoring wells in the Leading Edge area.The statistical analyses indicate a predominately downward trend of tritiumconcentrations in the groundwater monitoring wells in the vicinity of the VB 2/3 andPond area over time. Forty-three out of 49 monitoring well locations indicate areduction of tritium concentrations by 100%. In addition, all monitoring well locations indicate a reduction in tritium concentrations between the maximum detectedconcentration and the most recent concentration.

The following discussion outlines thestatistical analysis of each area in greater detail.VB 2 AreaTable 3.1 presents the latest tritium concentration detected in monitoring wells in theVB 2 area between December 2010 and December 2011. The statistical analyses indicatea predominately downward trend of tritium concentrations in the groundwater in thevicinity of VB 2. Tritium concentrations have been reduced by as much as 100%, from52,874 pCi/L in July 2006 to less than the LLD of 200 pCi/L in June 2012, as indicated atmonitoring well location BL-09D. Groundwater samples collected from monitoring wells in the VB 2 area are at levels less than the drinking water standard of 20,000 pCi/Land, in fact, all sample data, as of June 2012, are currently less than 318 pCi/L in theVB-2 area. Figures 3.2, 3.3, and 3.4 present this predominately downward trend intritium concentrations over time at select monitoring wells in the VB 2 area, BL-06 area,and RW-9 and RW-10 area, respectively.

VB 3 AreaTable 3.1 presents the latest tritium concentration detected in monitoring wells in theVB 3 area between December 2010 and December 2011. The statistical analyses indicatea predominately downward trend of tritium concentrations in the groundwater in thevicinity of VB 3. Tritium concentrations have been reduced by as much as 100%, from108,736 pCi/L in January 2006 to less than the LLD of 200 pCi/L in June 2012, asindicated at location VB-3-10D.

Groundwater samples collected from monitoring wellsin the VB 3 area are at levels significantly less than the drinking water standard of20,000 pCi/L, and, in fact, all sample data, as of June 2012, are currently less than249 pCi/L in the VB-3 area. Figure 3.5 presents this predominately downward trend intritium concentrations over time at select monitoring well locations in the VB 3 area.Exelon Pond AreaTable 3.1 presents the latest tritium concentration detected in monitoring wells in theExelon Pond area between December 2010 and December 2011. The statistical analyses016841 (45)7CONESTOGA-ROVERS

& ASSOCLATES indicated a predominately downward trend of tritium concentrations in thegroundwater near the Exelon Pond. Tritium concentrations have been reduced by asmuch as 100%, from 78,123 pCi/L in January 2007 to less than the LLD of 200 pCi/L inJune 2012, as indicated at location MW-135D.

Groundwater samples collected frommonitoring wells in the Exelon Pond area are at levels significantly less than thedrinking water standard of 20,000 pCi/L, and, in fact, all sample data, as of June 2012,are currently less than 1,000 pCi/L in the Exelon Pond area. 945 pCi/L (detected atmonitoring well P4D) was the highest tritium concentration detected in December 2011for the entire VB 2/3 and Pond area. Figures 3.6, 3.7, and 3.8 present the predominately downward trend in tritium concentrations over time at select monitoring wells in theNortheast of Pond area, the Northwest of Pond area, and the Southeast of Pond area,respectively.

Leading Edge AreaTable 3.1 presents the latest tritium concentration detected in monitoring wells in theLeading Edge area between December 2010 and December 2011. Tritium concentrations have been reduced by as much as 100%, from 969 pCi/L in September 2006 to less thanthe LLD of 200 pCi/L in June 2012, as indicated at location F-6D. Groundwater samplescollected from monitoring wells in the Leading Edge area are at levels significantly lessthan the drinking water standard of 20,000 pCi/L, and, in fact, all sample data arecurrently less than 529 pCi/L in the Leading Edge area. The statistical analyses indicatethat most monitoring wells in the vicinity of the Leading Edge have a downward trendof tritium concentrations in the groundwater.

Figure 3.9 graphically presents the tritiumconcentrations in the Leading Edge monitoring wells over time.3.2 CURRENT GROUNDWATER FLOW CONDITIONS Figure 3.10 provides the June 2012 groundwater contours for the VB 2/3 and Pond area.Since the shallow and deep monitoring wells are located within the same hydraulic unitand have historically indicated similar groundwater elevations, the shallow and deepmonitoring well elevations are contoured together.

Groundwater flow is generally tothe north. This figure also indicates the capture of groundwater around the ExelonPond due to the pumping of the Pond.016841 (45) 8 CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)8CONESTOGA-ROVERS

& AssocLATES 3.3 COMPARISON OF CURRENTGROUNDWATER QUALITY CONDITIONS TO HISTORICAL DATAFigure 3.11 provides the June 2012 tritium concentrations and presents the isolated areasof residual tritium.

The areas of residual tritium in the VB 2/3 and Pond area have beensignificantly reduced since January 2006. Currently, there are four isolated areas ofdetectable

tritium, three of which are directly south of the Exelon Pond and one to thenorthwest of the Exelon Pond. The isolated areas of detectable tritium which are locatedsouth of the Exelon Pond would be expected to flow into the Exelon Pond and beremediated by pumping or natural attenuation.

The isolated area of detectable tritiumto the northwest of the Exelon Pond would be expected to be remediated by naturalattenuation.

Figure 3.12 presents the January 2006 tritium plume versus the June 2012 residualtritium in the VB 2/3 and Pond area. This figure indicates a significant decrease intritium concentrations and impacted area since remedial activities began in June 2006.Tritium concentrations have been reduced from over 200,000 pCi/L to less than1,000 pCi/L. The January 2006 tritium plume has been reduced to four isolated areas ofresidual tritium in June 2012.3.4 EVALUATION OF THE REMEDIAL ACTIONThe remedial activities performed in the VB 2/3 and Pond area over the last 6 years havebeen very successful in decreasing the concentrations and reducing the extent of tritiumin groundwater.

During the course of pumping activities at the Exelon Pond and atRW-9 and RW-10, groundwater at select monitoring wells has been monitored on aquarterly basis for tritium concentrations and groundwater levels. The data collected over the last 6 years have been presented in Appendix B and on Figures 3.2 through 3.12.These data provide sufficient information to demonstrate the following regarding thecleanup of tritium in the VB 2/3 and Pond area:" There is no groundwater that contains tritium above the drinking water standard of20,000 pCi/L.* The current limits of detectable tritium (above 200 pCi/L) in this area have notextended beyond the Exelon owned property boundary.

" The maximum detected concentration in the entire area of VB 2/3 and the Pond as ofJune 2012 is 945 pCi/L.016841 (45) 9 CON ESTOGA-ROVERS

& ASSOCIATES 016841 (45)9CONESToGA-ROVERS

& AsSOCIATES

  • Only six out of 22 monitoring wells sampled during the June 2012 sampling eventindicated tritium concentrations above the LLD of 200 pCi/L.* The trend in tritium concentrations in routine sampling events has generally beendownward.

For 15 monitoring wells, either no trend could be statistically identified or there was not enough data available to determine a trend. One monitoring wellindicated an upward trend; however, this location indicated tritium concentrations below the LLD for the last four sampling events.* Since June 2006, the cone of influence (capture zone) around the Exelon Pond hasbeen successful in preventing further migration of tritium from this area.* Since January 2008, pumping and the resultant cone of influence (capture zone)around the two recovery wells (RW-9 and RW-10) have been successful inpreventing further migration of tritium from the area around BL-06.3.5 EVALUATION OF FUTURE GROUNDWATER CONDITIONS Predictive modeling simulations were performed in 2012 in order to determine the effectof a complete shutdown of all pumping activities (Exelon Pond and RW-9 and RW-10) inthe VB 2/3 and Pond area on tritium extent and concentrations.

Modeling ofgroundwater and tritium in this area indicates that the residual areas of detectable tritium located south of the Exelon Pond will dissipate within 0.3 year (120days).

Theareas of residual tritium to the northwest of the Exelon Pond will dissipate to aconcentration below the LLD of 200 pCi/L within 0.4 years (150 days). The isolatedareas of residual tritium in groundwater will not migrate off the Station's licensedproperty or onto private property at levels above the LLD of 200 pCi/L.Exelon initiated active pumping of groundwater based on the results from the predictive groundwater flow and transport modeling (CRA, August 2006, 2008). Pumping fromthe Exelon Pond directly with accelerated extractions (using extraction wells) in the areasouth of Exelon Pond was considered the most efficient remedial option to clean up thetritium plume associated with the releases from Vacuum Breakers 2 and 3. Thispumping operation has been ongoing since June 2006. Routine quarterly groundwater monitoring data from 2006 to 2012 have demonstrated that the tritium plume has beenshrinking over time to the current measured conditions.

It is anticipated that the remaining isolated areas of detectable tritium in groundwater will attenuate naturally over time, even if all pumping activities are stopped (both fromExelon Pond and from extraction wells RW-9 and RW-10). In order to verify that these018841 (45) 10 CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)10CONESTOGA-ROVERS

& Assoc[ATES residual areas of tritium in groundwater would naturally attenuate in the future withoutpumping, additional groundwater flow and transport modeling was performed usingJune 2012 data. The primary objective of these modeling efforts was to evaluate howlong it will take for the areas of residual tritium to dissipate (i.e., with tritiumconcentrations reduced to below the LLD of 200 pCi/L). The second objective of themodeling was to determine the migration pathway of the residual tritium.

Thememorandum presenting this groundwater flow and transport modeling effort isprovided in Appendix C.The modeling results demonstrate that the extent of the residual tritium areas willdecrease while the areas may migrate slightly further downgradient from the currentlocation.

The areas of residual tritium will eventually reduce to below the LLD of200 pCi/L within 150 days after the pumping cessation.

In addition, tritiumconcentrations will increase initially and then drop sharply to below the LLD(200 pCi/L).The following conclusions can be drawn based on the groundwater modelingsimulations:

  • It will take less than 150 days for the isolated areas of residual tritium ingroundwater in the VB 2/3 and Pond area to naturally attenuate to below the LLD of200 pCi/L after the current pumping operations at the Exelon Pond and theextraction wells are stopped; and* The isolated areas of residual tritium in groundwater will not migrate onto otheradjacent private properties after the pumping operations are shut down.016841 (45) 11 CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)11CONESTOGA-ROVERS

& ASSOCIATES

4.0 CONCLUSION

S The remedial activities in the VB 2/3 and Pond area have resulted in a significant decrease in tritium concentrations and reduction in the overall extent of tritium ingroundwater.

This reduction has occurred in the last 6 years through active pumpingand by the natural attenuation of tritium in the groundwater.

This Plan Completion Report documents the effectiveness of the remedial activities todate, as well as the ability of natural attenuation to eliminate the remaining isolatedareas of residual tritium.

Specifically, the following conclusions have been reached withregard to the remedial actions at the VB 2/3 and Pond area:* Concentrations of tritium in groundwater are less than the drinking water standardof 20,000 pCi/L." As of June 2012, tritium concentrations in groundwater have decreased to less than1,000 pCi/L and only four small isolated areas of residual tritium remain in the VB2/3 and Pond area.* Localized areas of residual concentrations of tritium above 200 pCi/L will notmigrate off the Station's licensed property or Exelon owned property, and will notimpact other off-Site private groundwater users.016841 (45) 12 CONEsToGA-ROvERS

& ASSOCIATES 016841(45) 12CONEsToGA-ROVERS

& AssocIATES 5.0 PLANNED COMPLETION ACTIVITIES As a final component of the remedial strategy at the VB 2/3 and Pond area, thegroundwater pumping activities will be shut down. In addition, the current quarterly groundwater monitoring program will be discontinued.

However, as part of the nuclearpower industry's voluntary groundwater monitoring
programs, Exelon will continuegroundwater monitoring of a number of key monitoring wells in the VB 2/3 and Pondarea. The monitoring wells that were associated with the quarterly groundwater monitoring program will be abandoned.

Each of these aspects is presented in moredetail below.Shutdown of Pumping Activities Exelon will terminate the pumping in the Exelon Pond and in recovery wells RW-9 andRW-10, and dismantle the equipment.

Upon shutdown of the pumping systems, thewater level in Exelon Pond is expected to recover upward to conditions prior topumping (i.e., similar to the surrounding static groundwater elevations).

It isanticipated that Exelon will restore the land surface and vegetation in the areas of thepumping equipment and discharge lines to at least the same conditions as prior toremedial activities.

Groundwater Monitoring ProgramWhile the current monitoring program will be discontinued, the VB 2/3 and Pond areawill continue to be monitored through Exelon's Radioactive Groundwater Protection Program (RGPP)3.

The RGPP is a program that meets the guidance provided by NEI07-07, ANI 07-01, and EPRI 1015118.

VB 2/3 and Pond area monitoring wells includedin the RGPP are presented in Table 5.1 and on Figure 5.1. The goal of the RGPPmonitoring is to ensure that any potential future impacts to groundwater are identified by Exelon in a timely manner.Monitoring Well Abandonment Monitoring wells in the VB 2/3 and Pond area that are not associated with the RGPPwill be abandoned and sealed. The monitoring wells to be abandoned and sealed arelisted in Table 5.2. Monitoring wells designated BL are considered blowdown linemonitoring well locations and will not be abandoned.

3 Monitoring wells that are currently above 200 pCi/L, but not included in the RGPP, will be monitored during RGPP sampling events. These monitoring wells will continue to be monitored until twoconsecutive sampling events indicate tritium concentrations below 200 pCi/L, at which time themonitoring well will be abandoned.

This includes VB-2-5D, VB-3-4D, P-4D, and P-13D.016841 (45)13CONESTOGA-ROVERS

& ASSOCIATES

6.0 REFERENCES

CRA, March 2006. Tritium Investigation, Exelon Generation, Braidwood Station,Braceville, Illinois.

CRA, April 2006. Investigation of Tritium in Groundwater in the Vicinity of VacuumBreakers 2 and 3, Braidwood

Station, Braceville, Illinois.

CRA, May 2006. Agreed Preliminary Injunction Order.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. Hydraulic Monitoring for the Will County Forest Preserve WorkPlan Braidwood Generating Station Braceville, Illinois.

CRA, November 2006. Minimize Impairment Plan for Vacuum Breakers 2 and 3Braidwood Generation, Station Braceville, Illinois.

CRA, December 2006. CRA Memorandum, Transient Groundwater Flow ModelCalibration and Transport Model Scenario Update.CRA, January 2007. Wedron Clay Till Investigation Report Braidwood Generating

Station, Braceville, Illinois.

CRA, January 2008. Simulation of Aggressive Remedial Option (VB-2 and 3), ExelonGeneration

Company, LLC Braidwood
Station, Braceville, Illinois.
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 toModularization Concepts and the Ground-Water Flow Process, United StatesGeological Survey Open-File Report 00-92, Reston, Virginia.
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 96-486, Reston, Virginia.

016841 (45)14CONESTOGA-ROVERS

& Assoc[ATES

McDonald, M.G. and A.W. Harbaugh, 1988. A Modular Three-Dimensional Finite-Difference Ground-Water Flow Model, United States Geological SurveyOpen-File Report 83-875.Pollock, D.W., 1994. User's Guide for MODPATH/MODPATH-PLOT, Version 3: Aparticle tracking post-processing package for MODFLOW, the U.S. Geological Survey finite-difference ground-water flow model: U.S. Geological SurveyOpen-File Report 94464.Rumbaugh, J.O and J.B Rumbaugh, 2011. Guide to Using Groundwater Vistas,Version 6, Environmental Simulations Inc., Herndon, Virginia.

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, andChemical Reactions of Contaminants in Groundwater Systems; Documentation and User's Guide. Prepared by University of Alabama, Prepared for US ArmyCorps of Engineers.

0i684i (45) 15 CONESTOGA-ROVERS

& ASSOCIATES 016841 (45)15CONESToGA-ROVERS

& AssocIATES 7-41000 20000LEGENDva-1 A VACUUM BREAKER LOCATIONi

~wANDBLWOW DOWN LINE7 '4 ittfigure 2.1VB 2/3 AND POND AREA SITE LOCATION MAPEXELON GENERATION BRAIDWOOD STATIONBraceville, Illinois0 CD//N-,j7241000 200M* ---APPROXIMATE BLOWOOWN PROPERTY UNEBLOWDOWNL UNEMAKEUP UNEVB-i A VACUUM BREAKERBL-li f') MID POINT MONITORING WELL LOCATION AND IDENTFIER VB-I-l & VACUUM BREAKER MONITORING WELL LOCATION AND IDENTIFIER figure 2.2LOCATION MAP FOR VB 2/3 AND POND AREAEXELON GENERATION BRAIDWOOD STATIONBrace vlle, Illinois LEGENDET FENCE UNESLOWDOWN LINEAPPROXIMATE PROPERTY BOUNDARYSLOWDOWN PROPERTY BOUNDARYSHALLOW SLOWDOWN LINE SAMPLING LOCATION,(A~ CELL84 0PAD00.T" m-o~uDEEP SLOWDOWN LINE SAMPLING LOCATIONVACUUM BREAKER LOCATIONPRIVATE WELUSURFACE WATER LOCATIONSHALLOW TEMPORARY WELL LOCATIONDEEP TEMPORARY WELL LOCATIONRECOVERY WELL LOCATIONPERMANENT MONITORING WELL LOCATIONSTAFF GAUGE LOCATIONIMW~NOTE-ONLY PRIVATE WELL LOCATIONS THAT ARECURRENTLY SAMPLED BY EXELON ARE SHOWN-ONLY MONITORING WELLS WITH DATA PROVIDED IN THISREPORT ARE PRESENTED ON THIS FIGUREVS-3-7Dova_,-,=2 figure 2.3MONITORING WELL AND PRIVATE WELL LOCATIONS VB 2/3 AND POND AREAEXELON GENERATION BRAIDWOOD STATIONBraceOvi/e,

///inois (58T00)~ © PW-13(58 7258588.!2 .........

589C ~ ~ -_0-* ......... .7Dfr(VB-2-3t VB,-2-0 VB-3-7D(590.88)

(590.17)

." 51 25) (581,59)VB-3-100

)B*#VB-2-7D (591.37)(591,02) 2L-2L) V " S-3(591.12)

(591 47)8L~ ~ 0 3 589 2-6L ) 1.35) XD ki ,10 20O 400ftCE UNE PW.a PRIVATE WELL LOCATIONLEGENDEXMTING PENVR-3 Avw 1 ,,;1" InPLANT PROPERTY UNE (2006)BLOWDOWN UNE SAMPUNG LOCATIONVACUUM BREAKER LOCATIONVACUUM BREAKER SAMPUNG LOCATIONMONITORING WELL LOCATIONSTAFF GAUGE LOCATION591 WELL. LOCATION~

RECOVERY WELL LOCATIONGROUNDWATER ELEVATION (ft AMSL)GROUNDWATER ELEVATION CONTOUR (It ASIL)GROUNDWATER FLOW DIRECTION MONITORM WELLDATATAKEN JANUARY&

2MOTO JANUARY 24.2Wlfigure 2.4GROUNDWATER LEVEL CONTOURS

-JANUARY 2006DEEP GROUNDWATER ZONEEXELON GENERATION BRAIDWOOD STATIONBrace wle, Illinois NIW9.3APAD 0RW.2 0-200-EXISTING FENCE UNEEXISTING PERIMETER DITCH UMITSBLOWDOWN UINEPLANT PROPERTY UNE (200M)DEEP SLOWDOWN UNE SAMPLING LOCATIONVACUUM BREAKER LOCATIONDEEP VACUUM BREAKER SAMPLING LOCATIONDEEP MONITORING WELL LOCATIONPRIVATE WELL LOCATIONDEEP TEMPORARY WELL LOCATION BACKGODRINIGNPOND SAMPLING LOCATION TRITIUMJANUAR)DEEP RECOVERY WELL LOCATION USING LCTRITIUM RESULT IN GROUNDWATER TRITIUM CONTOURSOURCE: CPA MARCH 2006 TRITIUM INVESTIGATION TRITIUM RESULTS 200,000 TO 250,000 (PICOCURIESIUTER)

TRITIUM RESULTS 100,000 TO 200,000TRITIUM RESULTS 60,000 TO 100,000TRITIUM RESULTS 40.000 TO 60M0OWTRITIUM RESULTS 20,000 TO 40,000TRITIUM RESULTS 10,000 TO 20.000TRITIUM RESULTS 5,000 TO 10.000TRITIUM RESULTS 200 TO 5.000TRITIUM RESULTS 0 TO 200(ND) NONDETECT BELOW 200 pCItLDUND TRITIUM CONCENTRATION:

200 PCIJL3 WATER STANDARD FOR TRITIUM:

20,000 PCULDATA FOR SAMPLES COLLECTED THROUGH30,o2006.

CONTOURS WEE figure 2.5OG VALUES.ESTIMATED TRITIUM RESULTS-JANUARY 2006DEEP GROUNDWATER ZONEEXELON GENERATION BRAIDWOOD STATIONBrace//le,

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