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U.S. Department of Energy
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Potential effects of surface coal mining on the hydrology of the West Otter Area, Ashland and Birney-Broadus coal fields, southeastern Montana

Technical Report ·
OSTI ID:5253766
The West Otter study area of the Ashland and Birney-Broadus coal fuelds extends from 2.5 to 14 miles south-southeast of Ashland, Montana. The area contains large reserves of Federal coal that have been identified for potential lease sale. A hydrologic study has been conducted in the area to describe existing hydrologic systems and to assess potential effects of surface coal mining on local water resources. Hydrologic data collected from private, observation wells, test holes, and springs indicate that shallow aquifers exist primarily within the Tongue River Member of the Fort Union Formation (Paleocene age) and within valley alluvium (Pleistocene and Holocene age). Sandstone beds are the principal aquifers that are used in the area, with the Knobloch coal bed in the Tongue River Member being a secondary source of supply. The primary use of ground water is for domestic supply and livestock watering. Surface-water resources consist principally of perennial flow in Otter Creek and intermittent flow in eight small basins sloping from the Tongue River-Otter Creek divide eastward to the Otter Creek valley. Mining of the Knobloch coal bed would remove three existing private wells and lessen the yield of two other wells; all five wells are used for watering livestock. After mining, water in the alluvium of Otter Creek might show long-term degradation in water quality as a result of waters leaching the soluble salts from the spoils material used to backfill the mine pits. 35 refs., 15 figs., 10 tabs.
Research Organization:
Geological Survey, Helena, MT (USA)
OSTI ID:
5253766
Report Number(s):
USGS/WRI-84-4087; ON: TI86900026
Country of Publication:
United States
Language:
English