Closure Strategy for a Waste Disposal Facility with Multiple Waste Types and Regulatory Drivers at the Nevada Test Site

The U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office (NNSA/NSO) plans to close the waste and classified material storage cells in the southeast quadrant of the Area 5 Radioactive Waste Management Site (RWMS), informally known as the '92-Acre Area', by 2011. The 25 shallow trenches and pits and the 13 Greater Confinement Disposal (GCD) borings contain various waste streams including low-level waste (LLW), low level mixed waste (LLMW), transuranic (TRU), mixed transuranic (MTRU), and high specific activity LLW. The cells are managed under several regulatory and permit programs by the U.S. Department of Energy (DOE) and the Nevada Division of Environmental Protection (NDEP). Although the specific closure requirements for each cell vary, 37 closely spaced cells will be closed under a single integrated monolayer evapotranspirative (ET) final cover. One cell will be closed under a separate cover concurrently. The site setting and climate constrain transport pathways and are factors in the technical approach to closure and performance assessment. Successful implementation of the integrated closure plan requires excellent communication and coordination between NNSA/NSO and the regulators. (authors)