Permits, Surface Water/Groundwater Baseline Sampling, and Analysis of Dewey-Burdock In Situ Uranium Project in Fall River County, South Dakota

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by Dan Hoyer,
Crystal Hocking,
Mark Hollenbeck,

Document Type: Proceeding Paper

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

Abstract: Powertech Uranium Corporation has proposed to conduct in situ mining within a uranium enriched ore deposit on the proposed permit area known as the Dewey-Burdock project. The project is located on the southwest flank of the Black Hills, approximately 12 to 15 miles north-northwest of Edgemont, South Dakota, and spans northern Fall River and southern Custer Counties. The proposed permit area consists of approximately 11,180 acres of private land and federal minerals. This paper describes the permit requirements for an in situ recovery project, results from the analysis of historic groundwater geochemistry data and water level, well test results, and the groundwater/surface water baseline sampling plan. Permits are required from the South Dakota Department of Environment and Natural Resources, Environmental Protection Agency, and Nuclear Regulatory Commission. A baseline sampling program meeting the requirements of all regulatory agencies has been implemented. The program will be completed by the third quarter in 2008. In an effort to understand the current groundwater geochemistry, historical Tennesee Valley Authority (TVA) data were analyzed. TVA monitored groundwater chemistry, flow, and water level from 1979 through 1984 in 150 wells within and adjacent to the permit boundary. Twenty-four geochemical maps were created that displayed the median value for water-quality samples. Descriptive statistics, box plots, and Kruskal-Wallis analysis were performed for wells which were considered to be statistically viable (i.e., having ten samples or more over the 5-year time period). Trilinear diagrams were also created for water-quality samples collected June 8, 1979, and September 12, 1979. Based on these geochemistry results, it was determined that the water chemistry does not vary much by date or member of the Inyan Kara Aquifer. Three well tests were performed by TVA. The original mining proposal envisioned developing a shaft-type mine. TVA performed two well tests to confirm the Inyan Kara could be dewatered. These tests significantly stressed the confined aquifer pumping 500 gallons per minute (gpm) and 200 gpm and lasted more than 10,000 minutes. The third test was in the Fall River Aquifer and was much smaller and shorter in duration. Type-curve matching using AQUASOLV was performed on the drawdown data from more than five observation wells in two different areas within the permit boundary.

Subject Headings: Permits | Federal government | Uranium | Field tests | Surface water | Rivers and streams | Groundwater | Aquifers | Pumping tests | Mines and mining | North America | South Dakota | United States

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