Transport Model Uncertainty and Sensitivity Analysis for Groundwater Releases of Radionuclides from Subsurface Nuclear Tests

by Andrew Wolfsberg,
Greg Ruskauff,
Bruce Crowe,



Document Type: Proceeding Paper

Part of: World Environmental and Water Resources Congress 2008: Ahupua'A

Abstract:

Uncertainty analysis of groundwater flow and transport models is a topic of considerable interest in the groundwater modeling communities. The Underground Test Area (UGTA) Project of the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office is in the process of assessing and developing regulatory decision options based on modeling predictions of contaminant transport from underground testing of nuclear weapons at the Nevada Test Site (NTS). The modeling task presents multiple unique challenges to the hydrological sciences. The structural and stratigraphic framework of the NTS is complex and consists of Paleozoic and older carbonate and clastic rocks overlain by a diverse assemblage of mid-Cenozoic volcanic rocks derived from large coalesced calderas. Lateral facies changes in the volcanic rocks are significant and the carbonate and volcanic assemblages are disrupted by basin-range faulting that locally formed thick basins infilled with alluvial deposits. Groundwater flow through the geologic units is predominantly within carbonate, volcanic, and alluvial aquifers with local interfingering aquitards that are all part of the internally drained Death Valley Regional Flow System of the southern Great Basin. Characterization of the hydrogeologic system is difficult and expensive because of deep groundwater in the arid desert setting.

Subject Headings: Sensitivity analysis | Groundwater flow | Volcanic deposits | Uncertainty principles | Groundwater | Site investigation | Rocks

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