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• 2.0 SEDIMENTATION CALCULATIONS <br />• <br />The sedimentation calculations for each pond are based on the Computer Modeling Program developed <br />by Civil Software Design, which is based on the Revised Universal Soil Loss Equation (RUBLE). <br />Sedimentation analyses are presented in the following sections. <br />2.1 RAINFALL FACTOR. R <br />A rainfall factor of ]0 was used for the Colowyo mine site based on the Isoerodent map of the Western <br />US presented in the SEDCAD4 Help menu and identical documentation discussed in Agricultural <br />Handbook No. 703. <br />2.2 SOIL ERODIIiILITY FACTOR, K <br />A conservative soil erodibility factor of 0.32 was used for all ponds. A comparison to dominant soil types <br />and associated K valuesis providedin Table 2. <br />TABLE 2 <br />SOIL ERODIIIILITY FACTOR <br />DOMINANT SOIL TYPE SOIL TEXTURE SOIL ERODIBILITY <br />FACTOR (K) <br />Cam s ass Series Loam 0.24 <br />Bumette Series Loam 0.28 <br />Work Series Loam 0.31 <br />Average 0.28 <br />2.3 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 shown in the SEDCAD4 printouts. <br />2.4 CONTROL FACTOR, C <br />The control factor is used to account for vegetative or mulch cover. The following values from <br />SEDCAD4 tables were utilized in the pond design evaluations (Schwab and Wamer, 1987): <br />TABLE 3 <br />CONTROL FACTOR <br /> <br />COVER COVER OR SLOPE TYPE VEGETATION CONTROL <br />FACTOR <br />Disturbed Fill Condition Freshly disked 0.95 <br />Reclaimed Topsoiled and Seeded No appreciable canopy, 0.45 <br /> 0 /o ground cover <br /> 1 to 2 Year Growth No appreciable canopy, 0.042 <br /> 60% groundcover <br /> 3+ Year Growth No appreciable canopy, 0.013 <br /> 80% ound cover <br />Undisturbed Undisturbed Woodland Effective cano 40-70% of area, 0.003 <br />Exh. 7-20-4 Revision Date: 3/29/07 <br />Revision No.: PR-02 <br />