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cover value adequate to control erosion. This value should then be acceptable and <br />defendable as a ground cover success criterion. <br />The Universal Soil Loss Equation (LISLE) is expressed as: <br />Where: <br />A=R*K*LS*C*P <br />A= soil loss in tons/acre/year (for our calculation, selected from <br />quantitative data from the West Elk Mine in 2011) <br />R= rainfall factor (in this case the 2 -year, 6 -hour Type II storm event <br />for Somerset, Colorado) <br />K= soil erodibility factor based on the soil types at the mine <br />(in this case torriorthents, Absarokee-Work loam, and Beenom- <br />Absarokee association; with K factors from 0.05-0.37) <br />LS= length of slope factor (in this case derived from quantitative <br />measurements of comparable locations at the West Elk Mine) <br />C= cover factor accounting for plant and litter cover on the ground <br />surface <br />P=control practice factor based on soil conservation practices <br />(assumed to be 1.0 as the areas of interest are native and not <br />managed) <br />For our purposes, the equation was rearranged to solve for C, yielding: <br />C=A/ (R*K*LS*P) <br />For the calculation, the following values were selected from published U.S. Department of <br />Agriculture, U.S. Department of Commerce, and Barfield, Warner and Hahn, 1983 and <br />quantitative field data collected from the area. <br />A= 13.68 <br />R= 33.30 <br />K= 0.2 <br />LS= 10.57 <br />P= 1.0 <br />Yielding: C=13.68/ (33.30*0.2*10.57*1) = 0.194 <br />When the calculated C value is interpolated from the EPA (1977) table "C" Factors for <br />Permanent Pasture and Rangeland, a ground cover of 20% is realized for a predominantly <br />graminoid vegetation community with no appreciable overstory canopy. The definition of <br />the percent ground cover (cover that contacts the surface) includes a random distribution of <br />mulch or vegetation and any mulch (litter) where it exists. <br />The proposed technical standard revegetation success criterion for "minimum ground cover <br />of living plants ... adequate to control erosion" shall be 20% total vegetation cover. Total <br />vegetation cover shall include live vegetation cover of all plants encountered during the <br />TR -77 H-9 Revised March 2019 <br />