Coupled Environmental Processes in the Mojave Desert and Implications for ET Covers as Stable Landforms

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Monolayer evapotranspiration (ET) covers are the baseline method for closure of disposal sites for low-level radioactive waste (LLW), mixed LLW, and transuranic (TRU) waste at the Nevada Test Site (NTS). The regulatory timeline is typically 1,000 years for LLW and 10,000 years for TRU waste. Covers for such waste have different technical considerations than those with shorter timelines because they are subject to environmental change for longer periods of time, and because the environmental processes are often coupled. To evaluate these changes, four analog sites (approximately 30, 1,000 to 2,000, 7,000 to 12,500, and 125,000 years in age) on the ... continued below

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Shafer, D.; oung, M. Y; Zitzer, S.; McDonald, E. & Caldwell, T. January 18, 2006.

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Monolayer evapotranspiration (ET) covers are the baseline method for closure of disposal sites for low-level radioactive waste (LLW), mixed LLW, and transuranic (TRU) waste at the Nevada Test Site (NTS). The regulatory timeline is typically 1,000 years for LLW and 10,000 years for TRU waste. Covers for such waste have different technical considerations than those with shorter timelines because they are subject to environmental change for longer periods of time, and because the environmental processes are often coupled. To evaluate these changes, four analog sites (approximately 30, 1,000 to 2,000, 7,000 to 12,500, and 125,000 years in age) on the NTS were analyzed to address the early post-institutional control period (the youngest site), the 1,000-year compliance period for disposal of LLW, and the 10,000-year period for TRU waste. Tests included soil texture, structure, and morphology; surface soil infiltration and hydraulic conductivity; vegetation and faunal surveys; and literature reviews. Separate measurements were made in plant undercanopy and intercanopy areas. The results showed a progressive increase in silt and clay content of surface soils with age. Changes in soil texture and structure led to a fivefold decline in saturated hydraulic conductivity in intercanopy areas, but no change in undercanopies, which were subject to bioturbation. These changes may have been responsible for the reduction in total plant cover, most dramatically in intercanopy areas, primarily because more precipitation either runs off the site or is held nearer to the surface where plant roots are less common. The results suggest that covers may evolve over longer timeframes to stable landforms that minimize the need for active maintenance.

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  • Unsaturated Soils Conference 2006, Carefree, Arizona, April 2006

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  • Report No.: CONF.01-2006
  • Grant Number: AC52-00NV13609
  • Office of Scientific & Technical Information Report Number: 862368
  • Archival Resource Key: ark:/67531/metadc793342

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  • January 18, 2006

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  • Dec. 19, 2015, 7:14 p.m.

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  • Dec. 5, 2016, 1:21 p.m.

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Shafer, D.; oung, M. Y; Zitzer, S.; McDonald, E. & Caldwell, T. Coupled Environmental Processes in the Mojave Desert and Implications for ET Covers as Stable Landforms, article, January 18, 2006; (digital.library.unt.edu/ark:/67531/metadc793342/: accessed September 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.