Publication Citation

USGS Series Water-Resources Investigations Report
Report Number 83-4225
Title Geochemistry and geohydrology of the West Decker and Big Sky coal-mining areas, southeastern Montana
Edition -
Language ENGLISH
Author(s) Davis, R. E.
Year 1984
Originating office
USGS Library Call Number (200) WRi no.83-4225
Physical description vi, 109 p. :ill., maps ;28 cm.
ISBN

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Abstract

In the West Decker Mine area, water levels west of the mine at post-mining equilibrium may be almost 12 feet higher than pre-mining levels. Dissolved-solids concentration in water from coal aquifers is about 1,400 milligrams per liter and from mine spoils is about 2,500 milligrams per liter. About 13 years will be required for ground water moving at an average velocity of 2 feet per day to flow from the spoils to the Tongue River Reservoir. The increase in dissolved-solids load to the reservoir due to mining will be less than 1 percent. In the Big Sky Mine area, water levels at post-mining equilibrium will closely resemble pre-mining levels. Dissolved-solids concentration in water from coal aquifers is about 2,700 milligrams per liter and from spoils is about 3,700 milligrams per liter. About 36 to 60 years will be required for ground water moving at an average velocity of 1.2 feet per day to flow from the spoils to Rosebud Creek. The average annual increase in dissolved-solids load to the creek due to mining will be about 2 percent, although a greater increase probably will occur during summer months when flow in the creek is low. (USGS)