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Western North Dakota contains several areas of known radioactive mineral deposits. Investigations conducted from the late 1940s to the late 1970s discovered several large areas of increased radioactivity in Bowman, Slope, Stark, Billings, and Golden Valley counties. Uranium and other radioactive elements were often found associated with beds of lignite.
Beginning in 1956, a few hundred tons of uraniferous lignite were shipped from North Dakota to processing plants. The mills were set up to process uraniferous sandstones and had difficulty processing the low grade ore lignites. In 1962, this problem was rectified by burning the uraniferous lignite in pits at the mine site, often by burning the bed, in place, after the overburden had been removed. The process reportedly took from 30 to 60 days, and diesel fuel and old tires were often mixed with the lignite to assure that it would burn sufficiently. The ash from the mines was then sent to Belfield or Griffith where it was further reduced by burning in kilns.
With respect to surface waters, the National Park Service (1997) found a total of 14 water quality monitoring stations (none within park boundaries) that determined uranium concentrations. However, these stations represented one-time samples from either 1983 (one station) or 1984 (13 stations). Most of these stations were located in tributaries south of the South Unit and had uranium concentrations well below the current drinking water criterion (20 ug/l). Two stations (THRO 0009 and THRO 0015), were located on Government Creek. Station THRO 0009 was the only station with a uranium concentration exceeding the criterion - in this case, the concentration was 200 times the criterion. This retrospective analysis by the National Park Service provides little information of value in an assessment of current water quality conditions; however, the fact that radiological parameters have not been measured on a consistent basis is noteworthy. Studies have been conducted by the Department of Energy into the locations and potential health risks of radioactive dust that spread from the uraniferous lignite burn sites, both at the mines and the Belfield and Bowman kiln sites. Park staff have expressed concern that the deposition of this radioactive dust may pose a water quality problem within the park. Radiological, water quality monitoring parameters could be included in the water quality monitoring program defmed by Project Statement THRO-N-200.001. Mining Historically, mining has been a viable economic activity in the region. This activity continues today and affects water quality in and around the park. Mining activities in this drainage basin have been and remain coal, sand and gravel, stone, and uranium, though uranium mining is not economically viable at this time and has ceased.
The potential exists for large-scale recovery and processing of lignite in western North Dakota. Lignite is a relatively low grade form of coal, and it appears that mineral deposits are located near the North and South units of the park. When it is mined, lignite-fueled power plants are generally built close to the fuel source.
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