Abstract
The Paradox Basin Study Region is coincident with a 12,000-square-mile salt basin of Pennsylvanian age in southeastern Utah and southwestern Colorado. The study region is being studied to evaluate the feasibility of siting a nuclear waste repository within its salt beds. A screening process is being used to identify sites potentially suitable and capable of being confidently characterized and licensed. During Phase I regional-level studies, a literature review was conducted to ascertain geologic characteristics pertinent to repository siting factors. On the basis of the regional screening results, four areas in southeastern Utah were selected as being suitable for more detailed study in Phase II: Elk Ridge and Gibson Dome, containing nearly horizontal bedded salt deposits; Salt Valley, containing a diapiric salt anticline; and Lisbon Valley, containing a non-diapiric salt anticline. During current Phase II area studies, the four study areas are being characterized in greater detail than in Phase I. Phase II will culminate in the identification of a potentially suitable location(s), if any, that will be recommended for study in still greater detail in a subsequent phase of work. The objective of this subsequent work will be to provide data and evaluations leading towards identification of potentially suitable site(s), if any, in the Paradox Basin.
The Gibson Dome #1 drillhole, a part of on-going area-level exploration, is providing 4-in. diameter continuous core to a projected total depth of approximately 6,400 ft. This drillhole will extend approximately 500 ft into Mississippian-age Leadville Limestone, which underlies the Pennsylvanian-age Molas Formation and salt-bearing Paradox Formation. Hydrogeological and geotechnical tests in GD-1 have been performed at various depth intervals to acquire in situ data on groundwater parameters above, in, and below the Paradox Formation, and on the mechanical behavior and hydrofracturing susceptibility of salt. Subsequent screening steps will consider results of Phase II work to delineate smaller potentially suitable areas (locations) having better-defined characteristics.