Some of the world's largest known coal deposits are present in the Gillette area, Wyoming. Recent demands for increased production of these resources emphasize the need for sound land-use planning, resource management, and environmental protection if future development is to be guided in the best public interest. Accordingly, the U.S. Geological Survey has begun a program of integrated geologic, hydrologic, and related studies to acquire basic land, water, and resource data. The results of the investigation are being prepared and published in forms designed for ready understanding by a wide range of potential users.

The study covers 1,500 sq mi in central Campbell County, and focuses on: (1) current land use and land and coal ownership; (2) location and extent of coal resources; (3) surface and ground water resources; and (4) potential environmental impacts of surface mining.

Geologic mapping and drill data indicate the presence of nearly a dozen individual coal beds of economic interest, parts of which are strippable. The Wyodak-Anderson coal bed is the deposit of greatest interest. This bed averages 50 to 100 ft in thickness in many places, lies less than 200 ft deep over approximately 75,000 acres of the study area, and contains more than 7 billion tons of sub-bituminous coal in the area where the overburden is less than 200 ft thick.

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The study area has several hundred domestic and livestock water wells, most of which are less than 500 ft deep. Water levels in these wells generally are less than 300 ft below the surface. Delineation of the potentially strippable coal zone and determination of its relation to the shallow aquifers permit an estimate of the probable effects of surface mining on ground water.

Acquisition and interpretation of similar types of geologic, hydrologic, and related data in other areas that have potential for resource development will provide decision makers with tools necessary for proper assessment of environmental impacts.

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