Groundwater Protection Project Greg Robison Project Manager Ed Sullivan Consulting Engineer June 23, 2008

Topics  Project Background  Technical Format  Catawba Example

Project Background  Industry Awareness Raised  Experiences Captured NRC in (July 2006)  NEI Executive Committee approved Groundwater Protection Initiative (July 2006)  Duke Groundwater Protection Project began work (August 2006)

Duke Perspective  This issue reminded us that public confidence and trust are critical to the continued successful operation of our plants  This issue caused us to look both inwardly at our daily activities and outwardly at our neighbors

Inward Focus  We saw a need to formalize & enhance our ground water protection program  Our aim is to give us assurance that we will be able to manage inadvertent releases to groundwater in a timely manner  This is NEI Industry Ground Water Protection Initiative Action 1

Outward Focus  We saw a need to develop a communication plan that more clearly covers all our neighbors – especially to assure we touch local communities, local government  Now go implement the plan  This is NEI Industry Ground Water Protection Initiative Action 2

Key Project Activities  Re-characterize the groundwater characteristics of each site  Install a series of radiological wells for early detection to allow remediation before materials leave owner property  Establish a formal ground water protection program  Extend communications plans to local level and communities

Project Progress  Completed installation of near-field and far-field well sets at McGuire (added 51 wells), Catawba (added 37 wells) and Oconee (added 26 wells)  Completed 2 of 3 site characterization reports for the three sites  Completed 1 of 3 numeric groundwater models for the three sites  Established formal Ground Water Protection Program  Developed and executed a refined Communications Plan

Project Example - Catawba  Background Information  Well Location Strategy  Project Results  Computer Model  Conclusions

What is Groundwater?  Groundwater is defined as “water below the surface of the earth.”  Groundwater resides within the pore spaces between soil particles and in rock fractures.  Groundwater is the source of drinking water for 48% of the U.S. population.  Groundwater is the source for 42% of irrigation water in the U.S.  Water-bearing zones are referred to as “aquifers.”

Saturated Media Fractured RockSoil

Typical Groundwater Profile

Piedmont Carolinas Geology/Hydrogeology  Regional Geology Silts present to depths of feet below ground surface. Fractured bedrock present below silts. Transition zone between soil and rock.  Regional Hydrogeology Flow occurs throughout entire geologic formation with localized preferential paths. Flow rates are generally slow ( ft/yr). Flow in fractured bedrock is unpredictable.

Potential Source Evaluation  Identify all potential sources Design drawings Site reconnaissance Site personnel interviews  Perform quasi-quantitative risk ranking Integrity (Engineering) Intensity (Radiation Protection) Impact (Hydrogeology Team)  Select highest risk sources for “attention” during hydrogeologic investigation

Well Location Considerations  Review existing site wells  Ensure near-field wells in vicinity of potential sources  Install far-field wells to monitor off-site migration  Fill gaps in hydrogeologic information

Well Location Considerations  Monitor each geologic unit  Evaluate vertical gradient  Evaluate drain effects  Monitor effects of any suspected historical releases

Well Location Results – CNS 7Existing Wells 17Near-field Wells 8Far-field Wells 6Gap Wells 6Assessment Wells 44Total

Existing Wells

Near-Field Wells

Far-Field Wells

Gap Wells

Assessment Wells

Groundwater Flow

Well Construction Depths  Water table wells  Shallow bedrock  Deep bedrock

Hydrogeologic Results – CNS  Confirmed pre-construction geologic investigation conclusions  Clarified effects of building drain system  Groundwater flow dominated by surface water and drain system

Radiological Results – CNS  Most recent tritium results: Below detection limit – 7 Between detection limit and standard – 32 Greater than standard – 1  One significant tritium source confirmed  No fuel pool release detected

Computer Model – CNS  3D Numerical Model – USGS MODFLOW  Grid size: 3300’ x 3600’  Four horizontal layers  Typical grid block = 50 ft x 50 ft  Typical grid block = 12.5 ft x 12.5 ft  Total cells = 55,680

Computer Model – CNS  Effectively replicates observed flow conditions  Simulates transport of postulated releases  Facilitates evaluation of various remedial responses  Demonstrates the effectiveness of the monitoring well network

Conclusions  Site hydrogeologic conditions are well understood (natural and plant-related)  Effective leak detection established for potential sources (near-field wells)  Site boundary monitoring in-place (far- field wells)  Tools in place for ongoing assessment (monitoring well network, computer model)