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Title: Closure Plan for Corrective Action Unit 110: Area 3 RWMS U-3ax/bl Disposal Unit, Nevada Test Site, Nevada

Technical Report ·
DOI:https://doi.org/10.2172/788421· OSTI ID:788421

This Closure Plan has been prepared for the Area 3 RWMS U-3ax/bl Disposal Unit Corrective Action Unit 110 in accordance with the Federal Facility and Consent Order (Nevada Division of Environmental Protection [NDEP] et al., 1996). The U-3ax/bl is a historic disposal unit within the Area 3 Radioactive Waste Management Site located on the Nevada Test Site (NTS). The unit, which was formed by excavating the area between two subsidence craters (U-3ax and U-3bl), was operationally closed in 1987. The U-3ax/bl disposal unit is scheduled for permanent closure under the Resource Conservation and Recovery Act as a hazardous waste landfill. Existing records indicate that, from July 1968 to December 1987, U-3ax/bl received 2.3 x 10{sup 5} cubic meters (8.12 x 10{sup 6} cubic feet) of waste. NTS nuclear device testing generated approximately 95 percent of the total volume disposed of in U-3ax/bl, the majority of which came from the Waste Consolidation Project (80 percent of the total volume) (Elletson and Johnejack, 1995). Area 3 is located in Yucca Flat, within the northeast quadrant of the NTS. The Yucca Flat watershed is a structurally closed basin encompassing an area of approximately 780 square kilometers (300 square miles). The structural geomorphology of Yucca Flat is typical of the Basin and Range Physiographic Province. Yucca Flat lies in one of the most arid regions of the country. Water balance calculations for Area 3 indicate that it is continuously in a state of moisture deficit. The U-3ax/bl Disposal Unit will be closed in place by installing a Resource Conservation and Recovery Act equivalent cover. Following cover construction a fence will be installed around the cover to prevent accidental damage to the cover. Post-closure monitoring will consist of site inspections to determine the condition of the engineered cover and cover performance monitoring using Time-Domain Reflectometry arrays to monitor moisture migration in the cover. Any identified maintenance and repair requirements will be remedied within 60 working days of discovery and documented in writing at the time of repair. Results of all inspections/repairs for a given year will be addressed in a single report submitted annually to the NDEP. Soil moisture will be monitored within the cover for a period of at least two years prior to establishing performance criteria for NDEP regulatory purposes.

Research Organization:
Bechtel Nevada Corporation (US)
Sponsoring Organization:
US Department of Energy (US)
DOE Contract Number:
AC08-96NV11718
OSTI ID:
788421
Report Number(s):
DOE/NV-647; TRN: US0110879
Resource Relation:
Other Information: PBD: 1 Aug 2000
Country of Publication:
United States
Language:
English