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given in the text of the report submitted by P7illard Owens and <br />• Associates concerning the hydrology of Pit 1 at the end of this <br />Appendix. <br />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 analysed, 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 stratum within the overburden and <br />the stratum immediately below the lowest coal seam to be mined <br /> <br />-35- <br />