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• Erodability <br />Erodability of the topsoil material is discussed for the <br />various soil types in the United States Department of Agriculture <br />Soil Conservation Service report on the proposed permit area <br />(Appendix E). Shales and lithologies containing high percentages <br />of clay-sized particles tend to have relatively higher erodability <br />factors than lithologies containing high percentages of sand or <br />silt-sized particles. <br />Swell and Compaction <br />An engineering compaction test was not performed on the <br />individual overburden samples analyzed, as this information was <br />determined to not be reliable in determining how the randomly dumped <br />spoil will compact in the backfill area. Instead, the general degree <br />of compaction of the spoil was determined by calculating the total <br />volume of overburden and coal removed from the mine and relative <br />• changes in the volume of the initial compacted backfill area between <br />air photos dated May 15, 1978, and October 7, 1979. By utilizing <br />these values, an average compaction factor of the overburden spoil <br />based on actual mining experience was calculated. The calculated <br />swell factor for compacted spoil backfill is 20 percent, which is <br />almost exactly compensated for by the coal volume removed. <br />Chemical Properties. <br />Chemical analyses of each <br />the stratum immediately below <br />performed in order to identify <br />acid-forming, toxic-forming or <br />analyses were performed by the <br />address is listed below: <br />stratum within <br />the lowest coal <br />those horizons <br />alkalinity-prop <br />following firm <br />the overburden and <br />seam to be mined were <br />which contain potential <br />3ucing materials. The <br />whose name and <br />• <br />-14- <br />