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Memo to Tony Waldron <br />Bowie No. 2 Geotechnical Adequacy <br />page 9 <br />If the riprap is to be placed and secured with grout, rather than with the <br />traditional gradational filter blanket, a specification and drawings for the <br />riprap clrading and grout placement shall be included within the permit <br />documentation. Further, since a grouted pan cannot adjust to consolidation of <br />the underlying materials, it is important that the foundation beneath the <br />channel pan be firm. Therefore, BRL shall commit to the inspection and density <br />testing of the prepared subgrade of the grouted riprap pan. <br />4.1.5 Material Balance/Material Stockpiles <br />WESTEC: requests that the topsoil stockpile just east of the toe of the waste <br />pile, and the coverfill stockpile located 600 east of the toe of the waste pile, <br />be exempted from sediment control and considered small area exemptions. BRL <br />also proposes to build the haul road to the waste pile without a sediment <br />control facility. Further, BRL requests a variance because a portion of these <br />facilities lie within 100 feet of the Right-of-Way for old State Highway 133. <br />Old Highway 133 appears to provide access for several of the neighboring <br />residents as well as the Bowie No. 2 mine. If Highway 133 were compromised <br />emergency access might be eliminated to the mine and the neighbors. BRL will <br />have to provide detail concerning the existing drainage conveyances along and <br />under old Highway 133 to demonstrate that changes within the mine permit <br />area, which affect water retention and routing will not overload the existing <br />ditches and culverts and compromise the old Highway. Further, BRL will have to <br />specify which alternative sediment control devices and techniques will be <br />implemented and at what specific locations. <br />4.3 Slope Stability <br />4.3.2 ~4aterial Properties <br />WESTEC considered four earthen materials in completing its slope stability <br />analysis; for the proposed waste pile. Strength parameters for the coal waste, <br />material "1" were determined by performing a direct shear test in the <br />laboratory. Strength parameters for existing sandstone-derived colluvial <br />material underlying the proposed waste pile, material "2", were theoretically <br />