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TRAPPER MINE <br />SEDIMENT LOAD DEMONSTRATION <br />BLOCK A, F, K &Z PITS RSAB 09-13 POST -MINING <br />Area <br />Curve Number <br />376.1 acres <br />Hydrologic Soil Group: <br />B (Permit C-81-010, Appendix Q, Section XII) <br />Cover Type: <br />Pasture, Grassland, or Range <br />Hydrologic Condition: <br />Good <br />CN (AMC II): <br />61 (SEDCAD 4 CN table - Other Agricultural Lands) <br />CN (AMC III): <br />78.8 (Barfield, Warner, Haan p. 84) <br />Erodibility Factor <br />K: <br />0.25 (Permit No. C-81-010, Appendix Q, Section XIII, Table E-4) <br />Control Factor <br />Type and Height of Canopy: <br />None <br />Canopy Cover: <br />None <br />Percent Ground Cover: <br />79.4% (Trapper Mine Phase II Bond Release App., Table 1.2-1) <br />CP: <br />0.014 (SEDCAD 4 table for Permanent Pasture, Rangeland) <br />Roughness Modifier: <br />0.65 (Contour farming operations, effective herbaceous cover, <br />contour ditches, livestock water tanks) <br />Modified CP: <br />0.009 <br />Average Slope and Slope Length <br />Weighted <br />Elevation Ave Slope <br />Length Change Sloe <br />A,F,K&Z-Pit RSAB 675 94 14.9 15.3 <br />'Derived from "Average Hydraulic Length and Block Slopes for (SL -19) Phase II Bond Release" Table <br />Time of Concentration <br />Land Use Category 1 Forest with heavy ground litter (overland flow) <br />Slope 15.3% <br />Length (ft) 675 <br />Tc (hrs) 0.191 <br />Sedcad inputs SL19 xls, A,F,K&Z RSAB Post Mining 8/4/2017 <br />