ABSTRACT
Much of the western coal reserves are sufficiently low in sulfur content to meet power plant air emission standards when burned; however, most of this coal can only be obtained by underground mining. The decision to use surface or underground mining is largely dependent upon such factors as depth of overburden, seam thickness, deposit size and local geology. Surface mining, often called "strip mining," requires removal of the overburden to allow recovery of the mineral directly from the surface. In each type of underground mining, the coal seam is reached by digging or boring either a vertical shaft, a horizontal portal, or a slanting tunnel. Major differences in mining techniques begin once the deposit is reached. Underground mining includes a number of techniques. Another new technique, borehole mining, is concerned with the problems of mining steeply pitched coal seams; it is an attractive possibility for some areas in the West.
