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• The embankment foundation areas were cleared of all organic matter, <br />all surfaces sloped to no steeper than 1V:111, and the entire foundation <br />surface scarified. The fill material was free of any large vegetation <br />r~iatter, or coal-processing traste. The placing and spreading of fill <br />material was started at the lowest point of the foundation and continued <br />in horizontal layers of such thickness as is required to facilitate com- <br />paction and meet all design requirements and specifications. <br />The downslope sides of the sediment ponds for Pit 4 consisted of <br />undisturbed rock. The stability of this side of the impoundment is influ- <br />enced by several factors. First, the excavation of the sediment pond <br />reduced the shearing stress on the containment rock. P, cross-section <br />through the pond (see Figure 9) shows the large amount of material removed, <br />resulting in a large reduction in shear stress. Second, because the <br />foundation rock dips downslope, there is a possibility that stored <br />water iaay seep out of the pond causing uplift pressures. These uplift <br />pressures are expected to be very small because the sandstone is relatively <br />tight. Finally, runoff water entering the ponds will contain sediment <br />which ••;gill tend to seal any seepaoe areas. In summary, the reduction in <br />shearing stress caused by excavation of the sediment pond is expected to <br />increase the stability of the downslope side of the pond. Other factors <br />influencing stability are expected to be insignificant. <br />2.05.3(5) To soil <br />• Vegetation will be cleared and grubbed from areas before topsoil <br />is removed. Topsoil will be removed from all areas to b2 disturbed prior <br />to further development. This includes haul roads, sediment ponds, over- <br />burden storage areas and areas to be mined. Topsoil will not be stripped <br />from the topsoil stockpile areas but vegetation will be cleared prior to <br />depositing any topsoil. The intent is to salvage all quality topsail <br />that can be used in reclamation. Topsoil stripping will precede the mining <br />front of the advancing hi9hwall. In late fall, this stripping distance <br />will increase so that topsoil can be salvaged prior to highwalT advancement <br />in winter. Experience has shown that topsoil removal is impractical in <br />winter conditions. <br />Topsoil will b•~ sttred in specially protected topsoil stockpile <br />areas as shown on the 'dining Plan Map. The stockpiles will be clearly <br />'.narked with signs until the material is removed. ks per the mining and <br />backfilling plan, much of the topsoil removed from one cut will immediately <br />be spread over another cut undergoing reclamation, thus reducing the <br />volumes of stockpiled topsoil. <br />The soils report has shown excellent quality soil to exist in most <br />areas to be mined. The depth of the topsoil removed will be clearly staked <br />in the field based on criteria described in the soils baseline study. <br />Minimum depths which will be removed are sho;vn on Table 5. <br />• <br />2-85 III-23 <br />