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<br />Dan Hernandez <br />RESULTS <br />Existing Conditions <br /> <br />- 2 - July 7, 1989 <br />LS = 12 Slope of the amendment area is 31% and <br />length-of-slope is 400 feet (see Appendix, <br />Hydrologic Supplement, Subbasin 8-1). The <br />maximum value of 25% slope shown on Table 2 (SCS, <br />1984) indicates a value of LS = 12 for a 400 foot <br />slope length. Because 31% is greater than 25%, <br />this value provides a conservative estimate of <br />soil loss. <br />C = 0.035 This value derives from Table 6 (SCS, 1984). <br />Review of aerial photographs indicates existing <br />tree plus shrub canopy cover to be 40%. A <br />conservative estimate of C = 0.035 results from a <br />canopy cover of 50% appreciable brush (2 meter <br />fall height) and grass-type ground cover of 60%. <br />E =RKLSCP <br />_ (75)(.17)12)(0.035)(1) <br />= 5.8 tons/acre/year <br />Condition 1 - MLRD <br />LS = 4 The maximum slope produced by mining is the <br />back filled areas where 4 to 1 slopes are <br />proposed. Minimum bench width is 50 feet. <br />Longer bench width would produce lesser overall <br />slope than the critical value of LS = 4 based on <br />25% slope and 50 foot length. <br />C = 0.038 The 35 trees/35 shrubs per acre is estimated <br />conservatively at 25% canopy cover and with a <br />grass-tYDe cover at 60% a value of C = 0.038 <br />results. Prior to any substantial tree canopy <br />growth a value of C = 0.042 results. <br />E initial = R K LS C initial P <br />_ (75)(.17)(4)(0.042)(1) <br />= 2.14 tons/acre/year <br />E final = R K LS C final P <br />_ (75)(.17)(4)(0.038)(1) <br />= 1.94 tons/acre/year <br />