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Peabody Sage Creek Mine — Drainage and Sediment Control Plan <br />Existing Seneca II Mine ditches and culverts that are part of the Peabody Sage Creek Mine postmine <br />• drainage control network, but not yet approved as permanent structures by CDRMS, include the <br />following: <br />Channels and Ditches <br />Culverts <br />• Channel PL -1 <br />• 9A <br />• Pre -Law Diversion Ditch <br />• 12A <br />• Northwest Diversion Ditch <br />• 13A <br />• Old Boneyard Diversion Ditch <br />• 15A <br />• Office Diversion Ditch <br />• 31A <br />• Ditch RA -D 1 <br />• 8A <br />• Ditch RB -D 1 <br />Sage Creek Coal Company will construct the following postmine channels for the postmine drainage <br />control network as part of the reclamation plan. In addition, three Peabody Sage Creek Mine <br />culverts will be included in the postmine drainage control network. <br />Channels and Ditches <br />Culverts <br />• Channel SCM -1 <br />• SC -10 <br />• Channel SCM -2 <br />• SC -11 <br />• Channel SCM -3 <br />• SC -12 <br />• Channel SCM -4 <br />• Channel SCM -5 <br />• • Ditch RA -1 -D1 <br />• Ditch RE-D1 <br />Designs for the postmine channels and culverts are presented in Appendix 2.05.3 -E2.H, Postmine <br />Channel and Culvert Designs. The stock ponds are all pre- existing Seneca II Mine structures. As- <br />built plans for the stock ponds are presented in Appendix 2.05.3 -E2.I, Stock Tank As -Built Report. <br />2.0 DESIGN METHODOLOGY AND ASSUMPTIONS <br />The hydrologic, hydraulic and sediment calculations used to design the sediment ponds, diversion <br />ditches, haul road ditches, culverts, postmine channels and stock ponds were generally performed <br />using SEDCAD4 — a computer program developed by Civil Software Design (Schwab, 1998) used <br />to evaluate storm water, erosion and sediment control management techniques. SEDCAD4 is the <br />most recent generation of the SEDIMOT II (Wilson et al, 1983) — SEDCAD+ (Schwab, 1988) <br />family of hydrologic models used for some of the earliest Seneca H Mine hydrologic calculations <br />and designs. Several of the diversion ditches found in the Seneca II Mine shop /warehouse area were <br />designed using Soil Conservation Service (SCS) triangular hydrograph techniques (SCS, 1975). <br />2.1 Hydrologic Calculations <br />SEDCAD4 calculates runoff and peak flow via a numerical modeling technique based on user <br />inputs of a design storm event (i.e., rainfall volume and duration, selection of rainfall distribution <br />is and convolution increment). Hydrographs are developed on a subwatershed basis with inputs of <br />2.05.3 -E2.5 <br />