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

2. Page 2 Page 2Title 81FY11 – 07/26/2011 – Page 2 Log No. 2011-230 Presentation Topics UGTA Strategy Overview Corrective Action Unit (CAU) Status/Changes

3. Page 3 Page 3Title 81FY11 – 07/26/2011 – Page 3 Log No. 2011-230 UGTA Closure Strategy Corrective Action Investigation (Phase I and II) –Corrective Action Investigation Plan (CAIP) –Data collection –Modeling –Contaminant boundary –Peer review

4. Page 4 Page 4Title 81FY11 – 07/26/2011 – Page 4 Log No. 2011-230 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)

5. Page 5 Page 5Title 81FY11 – 07/26/2011 – Page 5 Log No. 2011-230 Closure –Closure Report (CR) –Address boundary changes from model evaluation –Closure in place with long-term monitoring –Institutional controls UGTA Closure Strategy (continued)

6. Page 6 Page 6Title 81FY11 – 07/26/2011 – Page 6 Log No. 2011-230 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

7. Page 7 Page 7Title 81FY11 – 07/26/2011 – Page 7 Log No. 2011-230 Frenchman Flat Well Sites ER-5-5 ER-11-2

8. Page 8 Page 8Title 81FY11 – 07/26/2011 – Page 8 Log No. 2011-230 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

9. Page 9 Page 9Title 81FY11 – 07/26/2011 – Page 9 Log No. 2011-230 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

10. Page 10 Page 10Title 81FY11 – 07/26/2011 – Page 10 Log No. 2011-230 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

11. Page 11 Page 11Title 81FY11 – 07/26/2011 – Page 11 Log No. 2011-230 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

12. Page 12 Page 12Title 81FY11 – 07/26/2011 – Page 12 Log No. 2011-230 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

13. Page 13 Page 13Title 81FY11 – 07/26/2011 – Page 13 Log No. 2011-230

14. Page 14 Page 14Title 81FY11 – 07/26/2011 – Page 14 Log No. 2011-230

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16. Page 16 Page 16Title 81FY11 – 07/26/2011 – Page 16 Log No. 2011-230 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

17. Page 17 Page 17Title 81FY11 – 07/26/2011 – Page 17 Log No. 2011-230 Radiation Facts