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• prepared a well documented summary of the processes involved in coal processing. Among the findings of this review are that coal refuse materials following benefication normally contain higher sulfur levels than do the untreated coals. Cavallaro et. al. (1978) reported that the elevated trace element concentrations normally associated with coal processing are associated with the inorganic matter fraction and that concentrations of Cd, Cr, Cu, F, Hg, Mn, Ni, and Pb all increased in proportion to the amount of inorganic matter content. These trends were consistent for eastern as well as western coals. Hamblen et. al. (1980) studied various eastern and western coals and concluded that the sulfur content of westem coats as a rule was consideraby lower than that found in almost all eastern coals. Kuhn et. al. (1980) compared the trace element content of western coals from Montana, Arizona and Wyoming with various coals from the eastern and midwest coal producing areas and concluded that western coals contain much lower trace element concentrations and contain the largest number of nonleachable elements. The leachate from Montana coals were studied by Gerhart et. al. (1980) to determine the potential pollution impacts of runoff from coal stockpiles on the aquatic environment. They reported that compared to eastern coals, the leaching of western coal removes only a very small percentage of the metals present in these coals, and from a pollution standpoint, the metals leached from western coals are produced in such small amounts that they are relatively 'unimportarrt' as potential pollutants. • This review clearly demonstrates that the properties and associated environmental impacts of western coals are much different than associated eastern coals. LITERATURE ON THE ACIDIFICATION OF WESTERN COAL REFUSE AND SPOIL MATERIALS. The occurrence of acidic mine soils in the western states is considerably less common than found in the eastern states. Contrary to the somewhat popular belief, acidic mine spoils are much more common in the west than many have believed possible. In what was probably the earliest systematic reclamation research conducted in the western states, researchers at the University of Wyoming reported that acidity was the major factor affecting revegetation success on mine spoils in the Kemmerer Coal Field in southwestern Wyoming (Jacoby 1969 and May et. al. 1971). This early research demonstrated that as a whole the area could be considered as 'acidic.' The pH of spoil three years of age was reported to average 4.1, with a trend of increasing pH values as the spoil weathered. In a subsequent study of abandoned mine spoil in Wyoming, Singleton and Barker (1980) reported that acidic conditions had developed on 40 year old spoil while pH values on 16 year old spoil were all somewhat alkaline. They reported that acidic conditions (pH 5.77) had developed because the waste coal that was mixed into the spoil had oxidized. Acidic conditions developed on one site • because the initial calcium carbonate levels were very low and were quickly 6