Bill Wilborn UGTA Federal Sub-Project Director 2011 Community Environmental Monitoring Program (CEMP) Workshop July 26, 2011 Underground Test Area (UGTA)

Bill WilbornUGTA Federal Sub-Project Director

2011 Community Environmental Monitoring Program (CEMP) Workshop

July 26, 2011

Underground Test Area (UGTA) Overview

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Presentation Topics

• UGTA Strategy Overview

• Corrective Action Unit (CAU) Status/Changes

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UGTA Closure Strategy

• Corrective Action Investigation (Phase I and II)

– Corrective Action Investigation Plan (CAIP)

– Data collection

– Modeling

– Contaminant boundary

– Peer review

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• Corrective Action Decision/Corrective Action Plan

– Corrective Action Decision Document/ Corrective Action Plan (CADD/CAP)

– Use restriction boundary

– Regulatory boundary

– Model evaluation

UGTA Closure Strategy (continued)

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• Closure

– Closure Report (CR)

– Address boundary changes from model evaluation

– Closure in place with long-term monitoring

– Institutional controls

UGTA Closure Strategy (continued)

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Frenchman Flat

• FY 2010 completed Peer Review/Model accepted by State of Nevada Division of Environmental Protection (NDEP)

• Currently completing CADD/CAP – the first one for UGTA

• Building first two roads and pads for model evaluation wells

– American Recovery and Reinvestment Act funded

– Sites identified as ER-5-5 and ER-11-2

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Frenchman Flat Well Sites

•ER-5-5

•ER-11-2

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Yucca Flat• Initiating scoping of supplemental analysis for flow and

transport modeling (outcome from Preemptive Review)

– Models captured reasonable range of outcomes maximizing extent of contamination

– Low probability any water with radionuclide concentrations exceeding maximum contaminant level will leave Yucca Flat

– Most radionuclide inventory is retained within the vadose zone or saturated volcanics

– Extent of lower carbonate aquifer (LCA) exceedence volume (EV) is controlled by non-sorbing radionuclides from a small fraction of the tests

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Yucca Flat(continued)

– Tests with working points in the unsaturated zone contribute little to the LCA EV or to maximum southern extent of contamination in the LCA

– Key sensitivities with faults creating fast path from the volcanics to the LCA – major faults control the extent of migration

Conclusion: Extend Phase I to focus on major uncertainties and address during CADD/CAP model evaluation

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Rainier Mesa/Shoshone Mountain

• Continuing flow and transport model analysis and evaluation

• Concluded pre-emptive review held end of March for opening discussion with NDEP on path forward

– Similar strategy considerations for Yucca Flat need to be made for Rainier Mesa/Shoshone Mountain in regard to where focus on uncertainties should be

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Rainier Mesa/Shoshone Mountain

(continued)

– Tests Clearwater and Wineskin seem to dominate radionuclide transport to saturated zone; these two tests make up 25% of the Rainier Mesa/Shoshone Mountain inventory

– Path forward may be similar to Yucca Flat in that an extended Phase I may need to be implemented then move to CADD/CAP and model evaluation

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Pahute Mesa

• Will complete well development, testing, and sampling for three wells:

– ER-20-4 (one completion zone)

– ER-20-8 (two completion zones)

– ER-EC-12 (two completion zones)

• Phase II drilling campaign and geology

• ER-20-7

• ER-20-8

• ER-20-8 #2

• ER-EC-11

• ER-EC-12

• ER-20-4

• ER-EC-13

• ER-EC-15

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What Have We Learned to Date?

• Newly acquired data supports the conceptual model

• Contamination moves off Pahute Mesa in deeper units to stratigraphically higher units as caldera structure down drops the volcanics to the south

• The Benham Aquifer is hypothesized to be the main aquifer of concern at the leading edge of the contaminant plume

• Additional well installation and hydraulic testing are designed to increase confidence in our modeling strategy

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Radiation Facts