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<br />Memo to Dave Berry <br />Bowie No. 2 Gob Pile Laboratory Testing <br />page 2 <br /> <br />toe of the waste pile, material "4", were also deduced from SPT blow count <br />conversions. <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. This calculated static safety factor (SSF) narrowly exceeds the <br />required value of 1.5. If the ultimate waste pile volume, in excess of 225,000 <br />cubic yards of combined waste, coverfill and topsoil were to fail, it could <br />compromise the function and integrity of the sediment pond adjacent to the <br />waste pile toe, and it might compromise the drainage facilities adjoining State <br />Highway 133 and subject the public to an health and safety risk. For this reason <br />the Division requested that BRL obtain samples of each of the three earthen <br />material for which WESTEC assumed strength parameters and determine those <br />properties by appropriate laboratory testing. Based upon its "experience with <br />similar materials in this region, its belief that it considered "conservative <br />saturation condition of all of its foundation materials" in performing the <br />stability analyses, and its opinion that the required SSF value of 1.5 is <br />"relatively high", BRL declined to conduct any additional testing or to perform <br />sensitivity-style stability analyses. <br />Subsequent to the Division's issuance of its original adequacy comments for the <br />Bowie No. 2 Mine application, BRL submitted a "Preliminary Geotechnical Study" <br />of the surface facilities area performed by Maxim Technologies, Inc., as a <br />subcontractor to Morrison Knudsen, Inc. Having identified the proliferation of <br />mass wasting problems throughout the proposed surface facilities area, Maxim <br />performed extensive boring, sample collection and laboratory testing of <br />materials at the site. Maxim characterized the general colluvial materials <br />encountered throughout the site as a "Lean Clay with Gravel (CL-GC)", observing <br />that "the majority of the overburden materials at this site can be described as <br />a matrix of silty lean clay supporting scattered to numerous fragments of <br />sandstone." WESTEC referred to the corresponding colluvial cover on the <br />processing refuse pile site as "the colluvial sandstone above the Mancos Shale". <br />WESTEC chose to convert from blow count observation conducted during <br />