Slope angle distribution of coal beds with strippable reserves

Slope angles were determined in representative strip mining areas of Arizona, Colorado, Illinois, Kentucky, Maryland, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wyoming by personnel of the U.S. Geological Survey to provide the Strip Mining Task Force, assembled by the Council of Environmental Quality, with data relating to the slope angle distribution of coal beds with strippable reserves.

For the purpose of this study, slope determinations were made for 22 counties (table 1), selected by the Strip Mining Task Force, for coal beds known to contain strippable reserves as reported by Bureau of Mines Information Circular 8531, "Strippable Reserves of Bituminous Coal and Lignite in the United States." Available geologic maps that delineated coal bed outcrop lines on a topographic base were utilized for most slope angle determinations and coal resource reports provided additional data concerning the areas likely to contain recoverable coal reserves in the selected beds. The angles of slopes along which these coal beds occur were determined by measuring the spacing of topographic contour lines and were assigned to the appropriate slope categories selected for this purpose by the Strip Mining Task Force as follows: (A) 0-10°, (B) 10°-15°, (C) 15°-20°, (D) 20°-25°, and (E) 25°+. The overall sampling technique and measurement procedure are described in the following section and modification to this approach, necessitated by the availability and distribution of data, are described for each county. A list of source material used in compiling slope angles, slope distribution tables, and histograms are also included for each county.