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January 2002 Seneca II-W South Exfianrian * Drainage and Sediment Control Plan • Page 4 <br />3.0 SEDIMENTATION CALCULATIONS <br />The sediment calculations used to model the Seneca II-W (South Expansion) mine site were performed <br />utilizing the SEDCAD Computer Modeling Program developed by Civil Software Design. The <br />SEDCAD Computer model calculates annual sediment yield using the Revised Universal Soil Loss <br />Equation (RUBLE). The input parameters used in the sedimentation analyses are presented in the <br />following sections. <br />3.1 RAINFALL FACTOR, R <br />A rainfall factor of 30 was used for sediment pond designs at the Seneca II-W (South Expansion) <br />mine site. This value is consistent with bare, or disturbed, land that is easily eroded. In 2006 <br />SCC initiated updates to pond storage capacity demonstrations to account for the postmine <br />conditions which generate significantly less sediment yield. The updated demonstrations <br />used a rainfall factor of 10. <br />3.2 SOIL ERODIBILITY FACTOR, K <br />The soil erodibility factors for the subject site were determined based on soil survey information <br />(Nyenhuis, 1997). The values are shown on Table 2 (Soil Conservation Service, 1983). <br />TABLE 2 <br />SOIL ERODIBILITY FACTOR <br />Soil Type Soil Texture Soil Erodibility <br />Factor (K <br />Routt Cla Loam 0.28 <br />Winevada-S litro Com lex Loam 0.37 <br />Binco Cla Loam 0.28 <br />Coutis Silt Loam 0.37 <br />Aaber Cla 0.28 <br />S litro Loam 0.20 <br />Winevada Loam 0.43 <br />Foidel Silt Loam 0.28 <br />Sk a Silt Loam 0.28 <br />Roxal Variant 0.28 <br />Disturbed 0.16 <br />3.3 LENGTH-SLOPE FACTOR, LS <br />Input parameters to determine the LS factor were obtained from scaled maps of the watershed areas. <br />Values measured from the scaled maps are presented in the attached input parameter summaries. It <br />was assumed that the maximum overland flow length was 400 feet. <br />3.4 CONTROL FACTOR, C <br /> <br />The control factor is used to account for vegetative or mulch cover. The values utilized are shown on <br />Table 3 (Renard et al, 1996) (Schwab and Warner, 1987): <br />D~LVH * 165 S. Union Boulevard, Suite 410 * L.akemoorf, Colorado 80228 * (303) 763-5140 <br />TR-59 Revised 05/07 <br />