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A'urrurh~ ~~ iii'/: C9 CC - .Sediment t7~-(d Ucmuncn~atiun - Mn+.: 3 • G l he new Irngth-slope factor for the RUSLE subroutine is as follows: LS = r(slope ,Jucror) 'J 72.6 Where: n = Representative slope length.(ft)- - -- m = 0.6 for Slope <~~0 p ere ens m = 0.5 4 percent < slope <_ 10 percent m = 0.4 Slope = 4 percent m = 0.3 Slope < 4 percent Slope Factor is a piece-wise linear relationship with the slope break point being at 8 percent, as shown on Figure ~.>, Slope Factor for the RULSE in the SEDCAD+ Users Manual. The sediment graph is [hen routed to a structure using xn exponential decay procedure incorporating deposition of a particle size distribution. The eroded particle size distribution is an input item. Inputs to the sedimentology component of [he SEDCAD+ computer model include: • Particle Size Distribution • Rmtoff Volume • Peak Discharge • Soil Erodibility Factor • Representative Slope Length • Average Slope • Control Practice Factor r1 • • Sediment Specif;c Gravity Particle Size Distribution. Particle size distribution analyses were previously conducted by CYCC on three soil samples taken from the mine area. SEDCAD+ does not consider particles larger than 4.0 tnm as erodable, so the distribution Itas beets adjusted with respect to the fraction smaller than 4.0 tnm for input into the model. Analysis results are summarized in Appendix A, Table 1. Runoff Volume, V. Runoff volume is calculated by SEDCAD+, as previously described in the Hydrology Section, and is considered to be an intemal input. Peak Discharge, Q. Peak discharge is calculated internally within the SEDCAD+ program, as previously described, and is considered to be an internal input. Soil Erodibility Factor, K. The K factors for Block IJorth and Block South were determined using a weighted average of the pre-disturbance soil types found in Blocks North and South. As stated in the permit, CYCC is not certain of the topsoil salvage depth used at Mine 3 prior to June 1976. Approximately 20 inches of topsoil was stripped from the disturbed area between the years of 1976 and 1980. Based ott Routt County SCS designations, pre-disturbance soil types have the following factors: SOIL NAIt~ K FACTOR Buckskin Loam 0.32 au.n~ Routt Loatn 0.24, 0.32 Binco Silty Clay Loam 0.32 I Unnamed Loam - Aaberg Silty Loans 0.32 Splitro Sandy Loam 0.20 Parachute -Merino Complex 0.20 is\bond rel\m i ne3lscdltird m i ne3. doe