Refuse Contaminants from Preparation Plants

Coal refuse, varying in composition and size, is a function of the seam mined, the mining system, and the preparation system. Coal refuse consists mainly of unsalable coal, shale, bone, calcite, gypsum, clay, pyrite, or marcasite [20]. Disposal methods for coarse and fine coal refuse developed differently. Prior to modern coal preparation plants, coarse refuse was handpicked from the coal and discarded either back into the mine or deposited on the surface. When fine coal cleaning came into widespread use, it became more of an issue to deal with. Early practices were to discharge the "blackwater'' or liquid effluent containing solids into the nation's stream systems [20]. This is no longer acceptable, and the effluent must be filtered to remove the fine solids. Embankments are constructed using compacted coarse refuse material to impound fine coal slurry, and the impoundments serve as a filter to clarify this effluent as it flows through the permeable structure. These impoundments are also used as settlement basins and water-supply reservoirs.

The environmental impacts for coarse coal refuse sites include the nonproductive use of land, the loss of aesthetic value, water pollution, and air pollution. Many burning coal refuse sites in the United States are sources of local air pollution and safety hazards. Coal refuse disposal impoundments are constructed for the permanent disposal of any coal, rock, and related material removed from a coal mine in the process of mining. The environmental impacts of impoundments include the nonproductive use of land, the loss of aesthetic value, the danger of slides, dam failure, and water pollution [22]. Most coal waste impoundments in the United States, of which there are approximately 700, are found in the eastern United States, predominantly in West Virginia, Pennsylvania, Kentucky, and Virginia [21]. Most of the coal mined in the western United States is shipped without extensive processing; therefore, coal waste impoundments are rarely used there. The majority of coal from underground mines is processed before sale. Of the over 1 billion short tons of coal mined each year in the United States, about 600 to 650 million short tons are processed to some degree, 350 to 400 million short tons are handled in wet-processing systems, and 70 to 90 million short tons of fine refuse are produced [21]. It is estimated that 2 billion short tons of refuse are contained in impoundments in the United States [22].

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