Groundwater Protection Project

Greg RobisonProject Manager

Ed SullivanConsulting Engineer

June 23, 2008

Topics Project Background Technical Format Catawba Example

Project Background Industry Awareness Raised Experiences Captured NRC in 2006-13

(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 CarolinasGeology/Hydrogeology Regional Geology

Silts present to depths of 10-100 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 (10-100 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

7 Existing Wells17 Near-field Wells8 Far-field Wells6 Gap Wells6 Assessment Wells

44 Total

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)