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Memo to Tony Waldron <br />Bowie PJo. 2 Geotechnical Adequacy <br />page 10 <br />developed from interpretation of the Standard Penetration Test (SPT) <br />blowcounts recorded in the field. Strength parameters for the Mancos Shale <br />bedrock, material "3", were similarly deduced from SPT blowcounts. Strength <br />parameters for the historic coal mine waste fill material located beneath the <br />toe of the waste pile, material "4", were also deduced from SPT blowcount <br />conver.~ions. <br />WESTEC's stability analysis of the proposed Bowie No. 2 mine's coal waste pile <br />determined the overall static slope stability safety factor of the structure to <br />be 1.54. The corresponding pseudostatic factor of safety, assuming a <br />pseudo:~tatic horizontal acceleration factor of 0.1 g was calculated at 1.14. <br />This calculated static safety factor narrowly exceeds the required value of 1.5. <br />If the ultimate waste pile volume, in excess of 225,000 cubic yards of combined <br />waste, coverfill and topsoil were to fail, it could compromise the function and <br />integrity of the sediment pond adjacent to the waste pile toe. Further, since <br />the waste pile toe is within 150 feet of the right-of-way of old State Highway <br />133, it might compromise the drainage facilities adjoining that highway and <br />subject the public to an health and safety risk. <br />In consideration of the potential risk, BRL should obtain samples of each of the <br />three earthen material for which WESTEC assumed strength parameters and <br />determine those properties by appropriate laboratory testing. In the case of the <br />Mancos Shale (material "3") and the old coal mine refuse (material "4"), tests <br />should be performed in both saturated and unsaturated conditions to determine <br />the effect of ground water saturation. Sensitivity-style stability analyses can <br />then bey completed to determine the possible effect of unanticipated saturation <br />of the subject materials. <br />2.05.4 Reclamation Plan <br />2.05.4(2)(c) Backfilling and Grading <br />BRL suites that it will reclaim the mine facilities area, haul road and conveyor <br />corridor by returning the borrowed material from fill slopes to cut slopes. For <br />all the roads, benches and surface facility disturbances at this challenging site, <br />