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Hydrology of the Wibaux-Beach lignite deposit area, eastern Montana and western North Dakota

Water-Resources Investigations Report 83-4157

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Abstract

The geology and existing hydrologic regime of the Wibaux-Beach deposit area were studied to assess the potential impacts of proposed mining on the water resources. The Paleocene Harmon lignite of the Wibaux-Beach deposit constitutes a 50-square mile strippable reserve of about 1 billion tons. The Harmon bed and underlying discontinuous sand deposits in the lower Tongue River and upper Ludlow Members (Fort Union Formation) are the principal shallow aquifers in the area. Varying thicknesses of salt and clay separate the respective aquifers and act as confining units. Hydraulic and potentiometric data indicate that flow velocities are low, recharge is infrequent and of low magnitude, and vertical leakage is a major flux component. Water quality is quite uniform among the three aquifers. Most water is a sodium bicarbonate-sulfate type. Anomalously large sulfate, calcium, magnesium, and iron concentrations are generated by natural geochemical processes at the Harmon bed outcrop, but such concentrations do not persist far into the aquifer. Significant potentiometric declines in the Harmon lignite aquifer will extend for a few miles from active mines. Impact on the deeper aquifers will be minimal. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Hydrology of the Wibaux-Beach lignite deposit area, eastern Montana and western North Dakota
Series title:
Water-Resources Investigations Report
Series number:
83-4157
Edition:
-
Year Published:
1983
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
vi, 89 p. :ill., maps ;28 cm.