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7 Page 9 <br />BACK FILLING, SOIL STABILIZATION, COMPACTION, AND GRADING <br />The objective of the backfilling, soil stabilization, compaction, and <br />7 grading process is to provide a reclaimed surface which will result in <br />1 topographic features closely resembling the surrounding natural topography. <br />~ The steps to be taken in this program are described below. <br />DISPOSAL OF COAL WASTE <br />J After removal and stockpiling of the topsoil and liner material (Mancos <br />shale) in designated areas, coal waste will be dumped using 20 cubic yard <br />I end-dump tractor trailers. The spacing will be 11-12 feet laterally by <br />16-18 feet longitudinally. A Caterpillar D-7 or D-9 (depending on avail- <br />) ability) will distribute and compact the vaste~to two-foot~.~s. The <br />Caterpillar may also pull a sheep's foot compactor to compact the coal <br />waste to achieve at least 90Y, compaction (ASTM D 1557-78 compaction criteria). <br />The determination of what field placement methods used will be based upon <br />' further field testing. <br />All brush and grass will be removed prior to excavating the topsoil and <br />' liner material and will be either burned or otherwise disposed of. These <br />stripped materials will not be used in subsequent engineered fills. In <br />' areas where the Mancos shale is not exposed after removing topsoil, an im- <br />pezmeable liner will be formed by placing and compacting stockpiled liner <br />' material in level layers not exceeding eight inches in loose thickness, <br />moisture conditioned, and compacted near optimum moisture content to achieve <br />' a total liner thickness of at least two feet. Horizontally, the liner <br />material will be keyed at least five feet into competent Mancos shale. <br />' In areas where the liner material or waste material will be placed on slopes <br />equal to or flatter than 6:1 (horizontal to vertical), the upper six inches <br />' of exposed soil or rock will be scarified and recompacted. In areas of <br />slopes steeper than 6:1, horizontal benches eight feet or more in width <br />' with vertical steps of at least two feet between benches will be keyed at <br />least five feet into competent soil or rock. <br />1 If heavy rainfall occurs during the excavation process and water becomes <br />ponded, a portable sump pump will be used to collect the water. The water <br />