Case Studies from DOE Closure Sites: Emphasis on Reduction ... · 2 Office of Closure Support...

1

Case Studies fromDOE Closure Sites:

Emphasis on Reduction of Risk andRequirements for Long Term

Monitoring in Site Closure Design

Carol A. Eddy-Dilek and Brian B. Looney

Savanna River Technology Center

April 20, 2004

2

Office of Closure Support (EM-23)

qTechnical assistance from nationallyrecognized experts

q Focus is support to site with acceleratedclosure schedules

qRocky Flats and Ohio (Ashtabula,Columbus, Mound, Fernald) in 2006

q Parts of Oak Ridge Reservation in 2008q Sites are currently developing

Stewardship Plans

3

Intelligent Closure Design

qDesign of Remedial and Closuresystems can significantly impact longterm monitoring requirements

q Low-energy hydraulic controls can beused to contain and focus residualcontamination and optimize monitoringrequirements

4

Ashtabula Closure Project (ACP)

qRMI Extrusion Plant operated for DOEqRMI processed uranium between 1962

and 1968q Primary function was extrusion of

metallic uraniumq Extensive Contamination of Surface

Soilsq Localized U and solvent contamination

5

ACP Regulatory framework

q Cleanup of radioactive contamination (TCE, Tc-99) isbeing conducted under Decommissioning Plan

§ DP initially approved by NRC

§ Now under regulatory authority of Ohio Department ofHealth (ODH)

q TCE contamination

§ Waste Management Unit (WMU)

§ Estimated 1.3 acre groundwater plume

§ Ohio Environmental Protection Agency (OEPA) regulatoryauthority

6

7

Current Clean-up Levels

Total Uranium 30 pCi/g

Tc-99 65 pCi/g

TCE 5 ug/L

8

Hydrogeology

qVery low permeability glacial sedimentsqUpper till has thin sand and silt lenses

in the predominately clayey materialqResidual contaminants present in clayey

material

9

Closure Strategy

q Excavate source termqResidual contamination in groundwater

expected to exceed regulatory levelsq Install gravity induced pumping system

to pull back contaminated groundwaterfor treatment

qAmendments could be added to highpermeability backfilled material

10

Map view of Possible Closure System

cree

k

Pond

s (p

oten

tial

mon

itorin

g or

com

plia

nce

poin

t)

GeoDrain

excavated source and line(s)backfill w/ coarse fill or treatment bed

hill

horizontal wells or drains if needed

treatment bed or system as needed

amendments if neededto remaining soil &

groundwater

11

excavation

initial water level

constant operatingwater level-- free

draining or controlledmanually

Treatment Options

in situ usingamendments in

backfillor

ex situ using waterfrom drain orpumped well

Possible Configuration of Closure System

12

Advantages of Proposed Design

qHydraulic control of residual plumeqCollection of contaminated groundwater

focused to one collection pointqAmendments could be used to further

stabilize contaminationqHigh permeability fills would improve

gradients

13

Monitoring Design

q Initially monitor groundwater toestablish contaminant trends

qGroundwater at discharge point couldbe collected/monitored/treated

qMonitoring options include§ Periodic analysis of water samples§ Sensor at outfall location to measure

trigger levels§ Sorbent/integrated sampling system for

periodic analysis

14

East Tennessee Technology Park

15

East Tennessee Technology Park

qTwo thousand acres potentiallyimpacted by site activities

q Zone 1: Area outside operationalfences where most disposal activitiesoccurred

qCOC’s include VOC’s, heavy metals,radionuclides, PCB’s

16

Zone Map ofthe EastTennesseeTechnologyPark

17

Graded Approach

q Site developed graded approach for sitecharacterization, remediation, andclosure

q Four classes of soil unitsqDeveloped criteria for classificationqDeveloped strategy for characterizationqBlair Quarry chosen as pilot area for

approach

18

Soil Unit Classification

qClass 1 Soil Unit§ is, or was, impacted (potentially influenced

by contamination)§ the SU has moderate to high potential for

COC concentrations to exceed RLs; and§ insufficient evidence for no-action

qClass 2 Soil Unit.§ SU is, or was, impacted;§ there is low to moderate potential for COC

concentrations to exceed RLs; and§ insufficient evidence for no-action decision.

19

Soil Unit Classification

qClass 3 Soil Unit§ the unit is, or was, impacted§ there is no or very low potential for COC

concentrations to exceed RLs; and§ there is insufficient for no-action decision.

q Class 4 Soil Unit/Non-impacted.§ no evident anthropogenic impacts will be

designated as Class 4/Non-impacted.

20

Graded Approach

qAnticipated that only units found toClass 1 will require consideration forlong term monitoring.

qUse of graded approach limits greatlyareas to be monitored and focusesactivities on areas with higher risk.

qMovement of areas from Class 1 toClass 2 may be allowed based onresults of characterization studies.

21

Conclusions

qDesign of remedial and closure systemscan significantly impact long termmonitoring requirements

q Experience is that closure sites resistinnovations relative to baseline asclosure dates approach.