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<br />TABLE 1 <br />COVER COVER TYPE HYDROLOGIC <br />CONDCI'ION HYDROLOGIC <br />SOII. GROUP CURVENU?~IBER <br />Undisturbed Mountain Shrub Good C 41 <br /> Oak-Aspen Good C 41 <br /> Sagebrush Good C }7 <br /> Sagebrush Fair C 63 <br />Disturbed Topsoil Stripped Bare C 9i <br />Reclaimed Topsoiled and Seeded Bare B 86 <br /> 1 to 2 Year Grovrth Fair -Good B 61 - i8 <br /> 3+ Year Growth Fair -Good B 56 - 48 <br />Sources: SCS TR-55 Urban Hydrology for Small Watersheds June, 1986 <br />SEDCAD+ Version 3.1 Users Manual <br />Agreement between DMG and Colowyo Hydrologists <br />1.9 Base Flow <br />A base flow of 0.15 cfs was used Eor the Streeter Pond design. Abase flow of 0.03 cfs was used <br />• for the West Pit Pond design. Base flows were not used in any other pond design calculations. <br />Pumpmg of pit water will not occur during the 10 year, 24 hour storm events. <br />2.0 SEDIMENTATION CALCULATIONS <br />• <br />The sediment calculations used to model the Colowyo mine site were performed utilizing the <br />SEDCAD+ Computer Modeling Program developed by Civil Software Design. The <br />SEDCAD+ Computer model is based on the Revised Universal Soil Loss Equation (RUSLE). <br />The input parameters used in the sedimentation analyses are presented in the following <br />sextons. <br />2.1 Rainfall Factor, R <br />A rainfall factor of 19 was used for the Colowyo mine site. This factor is consistent with other <br />recent erosion analyses performed for the Colowyo Coal Company. <br />I~.ta;~mMWS.< <br /> <br />REVISED 11/93 <br />