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In order to conserve soil moisture, ensure stability, and control erosion on final graded <br />slopes the Division approved cut-and-fill terraces. Terrace benches were constructed to <br />control erosion prior to revegetation establishment and aze the only form of sediment <br />control left on the site as all sediment ponds have been removed and reclaimed. The four <br />sediment ponds at the site were replaced by treatment facilities consisting of terrace <br />benches constructed at two hundred (200) foot intervals. This proposal was supported by <br />the acquisition of field data which was used to refine specific factors contributing to the <br />soil loss equation, by a SEDCAD' run which predicted settleable solids values under this <br />treatment, and a revised post-mining topography map. The revision submittal was <br />approved as a package on August 30, 1988. <br />These terraces aze compatible with the post-mining land use, and will meet all the <br />requirements of this Section. (4.14.2(2)). <br />The Division approved the method and design specifications for covering ofacid-and <br />toxic-forming materials in order to prevent leaching into surface and groundwater and to <br />insure backfill stability. The Division reviewed Section C and Appendix D of the permit <br />application of compliance with the requirements of this Section. (4.14.3(2)). <br />During the original review, the Division identified several strata (coal seams, and <br />immediate over- and underlying strata) which contain some chemical constituents at <br />suspect (abnormally high) levels according to the Division. The parameters of particular <br />concern consist of selenium, boron, and molybdenum. <br />The disturbance of these overburden and interburden materials could impact the quality <br />of the ground and surface water, and affect the suitability of the overburden as a plant <br />growth medium. <br />The overlying and underlying strata of the Hoyle coal seam and the overlying strata of the <br />Sudduth coal seam were mixed within the spoils during mining. The strata underlying <br />the Sudduth seam is a shale. The weathering of this shale was minimal due to the low <br />permeability of the strata and the limited exposure at the pit bottom. Thus, the <br />contribution of dissolved solids to [he groundwater system would be minimal. Most of <br />the coal was removed from the site during mining and thus reduced the potential toxicity. <br />Given the operations plan for the Bourg Mine, overburden strata which have toxic <br />constituents would have been adequately mixed and diluted within the spoils. The <br />multiple handling of the overburden would provide this mixing, thus reducing the <br />potential that these elements would affect plant growth. <br />Oxidized coal from outcrops was selectively handled. To reduce the toxic effects of the <br />oxidized coal, this material was placed above the pre-existing water table and out of the <br />root zone of plants. The operator has supplied a map showing the pre-existing <br />Bourg Strip Mine. C-81-021 23 August 4, 1998 <br />