1. Brunswick Nuclear Plant Storm Drain Stabilization Pond Groundwater Investigation and Remedial Evaluation
Presentation Prepared and Presented by:
Silar Services, Inc.

2. Project / Presentation Overview
Investigation Status
Final Groundwater Investigation Report completed 3/2008
Review of ongoing monitoring data for groundwater and surface water
Quarterly reports for ongoing groundwater/surface water monitoring activities
Remedial alternative selected, engineering design process underway in 1st quarter 2008
Remedial Evaluation
Remedial Action Objectives (RAOs)
Potential Remedial Options
Summary/Questions

3. Objectives and Methodologies
Initial Scope
Characterize the nature and extent of tritium in groundwater adjacent to the SDSP in accordance with the Groundwater Protection Initiative (GPI);
Develop a conceptual site model for the SDSP that establishes the relevant transport pathways and potential receptors associated with the release of tritium from the SDSP
Establish a comprehensive groundwater monitoring program
Based on results of investigation, additional scope included:
Determine applicable or relevant and appropriate requirements (ARARs) and establish remedial action objectives (RAOs)
Screen and evaluate remedial alternatives available to address site conditions and RAOs

4. Field Investigation Summary
Completed an initial evaluation of data and physical characteristics of the SDSP and surrounding environs
Established access to remote, wooded areas around the SDSP that required investigation
Installed a network of 15 shallow groundwater monitoring wells, 7 intermediate-depth wells,1 deep bedrock monitoring well, and 6 marsh wells (additional pre-existing wells were evaluated and incorporated into the monitoring network, where appropriate)
Collected soil samples for geotechnical parameters
Completed “preliminary” groundwater monitoring and real-time data evaluation throughout the effort
Identified site conditions and data gaps in real time
Allowed for completion of the groundwater investigation during a single mobilization

5. Field Investigation Summary (continued)
Completed an initial hydraulic characterization of the groundwater aquifers via pump tests and rising head slug tests
Completed a 3-month synoptic hydraulic study to evaluate hydraulic relationships between the SDSP, groundwater aquifers, and surface water (tidal effects)
Developed a conceptual site model and analysis of transport pathways for all associated groundwater pathways
Completed area reconnaissance to identify off-site groundwater uses/withdrawals

6. Development of the Groundwater Monitoring Program
Designed and installed a GeoSmart groundwater monitoring system consisting of a dedicated bladder pump, teflon® tubing, heavy duty bladder, and integrated well head system
Facilitate consistent, program-wide hardware and sample collection methodology
Provide user friendly interface and rugged hardware for long-term deployment
Appropriate for collecting groundwater samples consistent with USEPA low-flow methodology
Established a monthly groundwater monitoring program for associated shallow, intermediate, deep, and marsh wells
Trained facility personnel to properly perform monthly groundwater sampling activities

7. Groundwater Investigation Summary
Final Groundwater Investigation Report submitted in March 2008
Findings
Area underlain by 3 individual aquifers (shallow, intermediate and deep)
Widespread tritium impacts in shallow, isolated impacts in intermediate, no impacts in deep.
Tritium observed in marshes and adjacent creeks
Site hydraulic are such that impacts will migrate off-site
Shallow to Nancy’s Creek and Shallow to Intermediate to Off-site
Migration of tritium in on-site groundwater to off-site groundwater has not been observed
SDSP Area Achieves EPRI Program Level 3 Status

8. Monitoring Well and Hydrogeologic Cross Section Location Map

9. Hydrogeologic Cross Section

10. Groundwater Flow – Shallow Aquifer

11. Shallow Aquifer Groundwater Results for Tritium (pCi/L) - October 2007

12. Trend Analysis - Shallow Aquifer

13. Result of Reducing Source Term
Elimination of Primary Source of Tritium to SDSP
(June 2007)
Reduction of SDCB concentrations from upwards of 1,000,000 to 50,000 pCi/L.

14. Groundwater Flow – Intermediate Aquifer

15. Intermediate Aquifer Groundwater Results for Tritium (pCi/L)

16. Trend Analysis - Intermediate Aquifer Groundwater

17. Groundwater Flow – Deep Aquifer

18. On-going Monitoring Weekly monitoring of surface water
17 surface water monitoring waypoints
Monthly monitoring of groundwater
40 groundwater monitoring stations
Findings
Tritium concentrations in groundwater generally consistent with initial results
Reduced source term to the pond appears to have positive result on groundwater concentration at the source
Increasing concentration of tritium in groundwater samples collected from intermediate monitoring well ESS-19B raises concerns regarding vertical migration from shallow to intermediate aquifer (i.e. potable supply aquifer)
Detectable concentrations of tritium in surface water samples

19. Off-site Detections in Surface Water

20. Evaluation of the Marsh and Creek
SDSP tritiated water seeps through dike and transports to marsh
Groundwater flows from the SDSP through the upper sand into the creek as baseflow
Ongoing evaluation to determine appropriate method, model and model inputs to facilitate dose calculations associated with unmonitored release to the adjacent creeks accounting for these two mechanisms
Groundwater flow / tritium fate and transport modeling
Use of ongoing monitoring data to calculate dose per unit time
Model to account for tidal effects and heterogeneity

21. Remedial Options – Remedial Action Objectives
Remedial Action Objectives (RAO) were developed for the Stabilization Pond release based on Federal, State and Local rules and regulations along with industry best management practices
RAOs include:
Reduce the continual migration of tritium in groundwater on-site and off-site to protect human health and the environment
Control future uncontrolled releases of tritiated water through the SDSP to the environment
Reduce the concentration of tritium in groundwater to a concentration less than the Federal MCL of 20,000 pCi/L

22. Remedial Options – Potential Remedial Actions
Six remedial actions were evaluated in the Final Report including:
Monitored Natural Attenuation (MNA)
Containment (Barrier Wall) with MNA
Containment (Impoundment) with MNA
Containment (Barrier Wall and Impoundment) with MNA
Site-wide Groundwater Extraction with MNA
Focused Groundwater Extraction with Containment (Impoundment) and MNA
Each alternative was evaluated against the primary criteria of: effectiveness, implementability, and cost.

23. Remedial Options – Alternative 1 - MNA
MNA involves no active remedial measures and relays on natural processes to achieve the RAOs
Assumes status monthly monitoring to plant closure
Evaluation criteria summary
Effectiveness – will not meet any of the RAOs, provides no protection to human health or the environment
Implementability – easily implemented, continue monthly monitoring, no construction activities
Leads to high decommissioning costs
Summary – Alternative 1 will not achieve the RAOs

24. Remedial Options – Alternative 2 - Containment (Barrier Wall) with MNA
Alternative 2 involves installation of low permeability vertical barrier wall to control horizontal flow of tritiated groundwater in the shallow aquifer
Assumes wall would be construction around ~90% of the pond, approximately 6,400 ‘ long, 45’ deep and 3’ wide
Evaluation criteria summary
Effectiveness – shallow groundwater within the impoundment would be controlled, but increases vertical migration into deeper aquifers
Implementability – using fairly typical construction equipment, 6-12 months
Summary – Alternative 2 would control shallow groundwater within the impoundment, it would not achieve the RAOs since it would not address impacted groundwater outside the impoundment or the vertical migration of shallow groundwater to the intermediate aquifer

26. Remedial Options – Alternative 3 - Containment (Impoundment) with MNA
Alternative 3 involves construction of a low permeability impoundment within the SDSP to control the future uncontrolled releases of tritium into the environment
Assumes lined impoundment (2 liner systems evaluated), 350,000 sq.ft., mg capacity.
Evaluation criteria summary
Effectiveness – will control future releases to the environment, will not effect continual migration of tritiated groundwater
Implementability – with fairly typical construction equipment, 6-12 months
Summary – Alternative 3 would control future releases to the shallow aquifer, however it would not achieve the RAOs since groundwater outside the impoundment would continue to migrate horizontally and vertically on-site and off-site.

28. Remedial Options – Alternative 4 - Containment (Barrier Wall and Impoundment) with MNA
Alternative 4 involves the primary element of Alternatives 2 and 3.
Assumes construction of a barrier wall and impoundment (non-RCRA liner) as previously described
Evaluation criteria summary
Effectiveness – Shallow groundwater within the barrier wall will be controlled and future uncontrolled releases to the environment through the SDSP would be eliminated
Implementability – with fairly typical construction equipment, 6-12 months
Summary – Alternative 4 would control shallow groundwater within the impoundment and eliminate continual releases through the SDSP, however it would not achieve the RAOs since it would not address impacted groundwater outside the impoundment or the vertical migration of shallow groundwater to the intermediate aquifer.

30. Remedial Options – Alternative 5 – Site-Wide Groundwater Extraction with MNA
Alternative 5 involves extracting groundwater from the shallow aquifer throughout the impacted area to achieve the RAO of 20,000 pCi/L
Assumes – installation of over 200 extraction wells with total withdrawal of 154,000 gpd
Evaluation criteria summary
Effectiveness – would control the off-site migration of tritium in the shallow groundwater
Implementability – with fairly typical construction equipment, significant long-term O&M
Summary – Alternative 5 would control horizontal migration of groundwater in the shallow aquifer to off-site receptors, it would not eliminate uncontrolled releases through the SDSP or achieve the RAOs.

32. Remedial Options – Alternative 6 - Focused Groundwater Extraction with Containment (Impoundment) and MNA
Alternative 6 involves focused groundwater extraction to control off-site migration and installation of an impoundment within the SDSP to control the future uncontrolled releases of tritium into the environment
Assumes elements of Alternative 3 and up to 50 extraction wells to control off-site migration and restore aquifer
Evaluation criteria summary
Effectiveness – Would be effective in elimating future releases and controlling migration of tritiated groundwater
Implementability – with fairly typical construction equipment, some long-term O&M
Summary – Alternative 6 would achieve all RAOs.

34. Selected Remedial Alternative
Alternative 6 - Focused Groundwater Extraction with Containment (Impoundment) and MNA is the only remedial option that could achieve the RAOs in the long term. Alternative 6 will:
Reduce the continual migration of tritium in groundwater on-site and off-site to protect human health and the environment by:
constructing a lined impoundment thereby eliminating the on-going source of tritium impacts (percolation through the bottom of the pond) and
extracting groundwater at strategic locations to control the horizontal migration of shallow groundwater to off-site receptors (i.e. Nancy’s Creek) and the vertical migration into the intermediate aquifer.
Control future uncontrolled releases of tritiated water through the SDSP to the environment by:
constructing a lined impoundment thereby eliminating the on-going source of tritium impacts (percolation through the bottom of the pond).

35. Selected Remedial Alternation - con’t
Reduce the concentration of tritium in groundwater to a concentration less than the Federal MCL of 20,000 pCi/L by:
Controlling the source (i.e. eliminating future loading of tritiated water into the shallow aquifer by constructing a lined impoundment) and extracting shallow groundwater with elevated concentration of tritium.
Extracted groundwater will be conveyed to the impoundment for subsequent releases to the intake canal under NDPES permit.
Groundwater extraction with MNA could reduce the tritium concentrations in groundwater below 20,000 pCi/L thereby reducing decommissioning costs.
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36. Highlights of the Investigation Process
The dedication of the Progress Energy management team facilitated the successful implementation of the investigation program
Development of CSM utilizing up-to-date knowledge base leads to updated FSAR and site understanding
Avoided pitfalls associated with reliance on historic data collected by others
Established low-maintenance, easy to use groundwater sampling system, procedure, and monitoring program implemented by internal resources
Improved operational performance as a result of the awareness and identification of SSCs associated with SDSP and BNP
Successful media and public relations activities through open house forums and regular contact with local media and officials

37. Highlights of the Remedy Selection Process
Remedial evaluation incorporated detailed short and long-term financial, technical, and environmental considerations
Selected remedy incorporates long-term management considerations and environmental objectives with fiscally-responsible remedial approach
Selected remedy incorporates existing NPDES-permitted outfall such that it constitutes a redevelopment rather than a new source/discharge
Selected remedy is flexible such that pre-design activities can determine treatment requirements, impoundment sizing, well spacing, etc.

38. Summary/Conclusions
Widespread shallow groundwater impacts due to uncontrolled releases for the SDSP
On-going monitoring indicates impacts off-site in Nancy’s Creek and increased migration into the intermediate aquifer
Six remedial options evaluated
Alternative 6 - Focused Groundwater Extraction with Containment (Impoundment) and MNA would achieve the RAOs

39. Questions