Transcript Document

Underground Test Area
(UGTA) Overview
Bill Wilborn
UGTA Federal Sub-Project Director
2011 Community Environmental Monitoring Program
(CEMP) Workshop
July 26, 2011
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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UGTA Closure Strategy
(continued)
• Corrective Action Decision/Corrective Action
Plan
– Corrective Action Decision Document/
Corrective Action Plan (CADD/CAP)
– Use restriction boundary
– Regulatory boundary
– Model evaluation
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UGTA Closure Strategy
(continued)
• Closure
– Closure Report (CR)
– Address boundary changes from model
evaluation
– Closure in place with long-term monitoring
– Institutional controls
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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 nonsorbing 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
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