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<br />~~ 4.0 DESIGN ASPECTS <br />The following sections detail site-specific aspects of the construction of the proposed coal <br />mine waste bank and ancillary facilities at the Sanborn Creek Mine. The proposed waste bank <br />was designed to optimize the available space and accommodate maximum coal mine waste <br />quantities, while incurting minimal disturbance to the surtounding landscape. Calculations for <br />the height -volume relationship of the waste bank are included in Appendix C. <br />4.1 CONSTRUCTION <br />4.1.1 General <br />Construction of the proposed coal mine waste bank begins with the sediment pond, sediment <br />pond access road, and upland diversion ditch. A plan view of the waste bank is shown on <br />Drawing 95255.01. The sediment pond is designed to collect storm water runoff and the <br />associated sediment transported with it. Discussion of the sediment pond requirements is <br />presented in Section 4.2 of this doctunent. Upland diversion v~n7 be constructed on an existing <br />road above the proposed waste bank, as shown on the drawings. Diversion d"itches are <br />• discussed in detail in Section 4.1.4 of this document. The toe was sited to begin at a <br />relatively flat area at Elevatan IEI.) 8,050 feet (ft1 in the center of the draw. This area should <br />be stripped of topsoil and stockpiled in the Eik Creek topsoil stockpile and used later as part <br />of the reclamation process. Generally, during typical wastebank construction topsoil should <br />be removed in srttail quantities ahead of the devektpitg waste bank to control erosion potential <br />of the stripped, unvegetated subsurface and placed directly on exposed coal mine waste that <br />is ready for reclamation. Inipally, stripping ahoukl proceed whhin the waste bank foot print <br />to Ei. 8,100 h. It is recommended that 4 tertaces bs constructed to approximately 10 feet <br />wide within this initial stripping area. These terraces will aids in providing stability for the <br />waste bank. These tertaces should be placed at elevations shown on Drawing 95255-02, at <br />ten-foot elevation increments. Terrace details aro shown on Drawing 95255-03. <br />An underdrain system should be started during initial wnstruction which will discharge flow <br />into the sediment pond. The underdrain system is discussed in detai in Section 4.1.2. The <br />proper placement of the first coal mine waste lifts is critical to overall stability of the waste <br />~ bank. Compaction of the material should be a minimum of 90 percent of the maximum dry <br />96256/1~21.RPT Coil Mira W~tt~ 8~nk DMpn far tM S~nDOrn trek MM <br />oatoMr t 99a wt¢sTttc, i~+a. e <br />