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<br />Dan Hernandez - 1 - July 7, 1989 <br />2. Replacement Proposal. This plan is for replacement of trees at the <br />existing ensity o 80 trees per acre, no shrubs, and grasses at <br />60~ ground cover. This composition was selected to approximate the <br />undisturbed "forested" condition. <br />3. DOW Proposal. The Division of Wildlife recommendeo, for wildlife <br />purpo~Tiat 35-45 trees per acre, no shrubs, and grasses be used <br />for revegetation. The grasses would provide forage and the trees <br />would provide cover. No shrubs were included as surrounding areas <br />provide sufficient shrub for species utilizing this cover and <br />forage. The Colorado State Forest Service concurred with the value <br />of 40 (average) trees per acre. Aground cover of 60% grasses was <br />used to approximate existing conditions. <br />Soil loss estimates were calculated for each of the three (3) proposed <br />post-mining reclamation conditions in units of tons per acre per year. In <br />addition, an estimate of the existing pre-mining condition of soil loss was <br />calculated for comparative purposes. In order to make these estimates, <br />parameter values in the USLE must be specified for each condition. <br />Parameter Selection <br />The USLE soil loss equation is written as: <br />A=RKLSCP <br />Where A = Soil loss (tons/acre/year), <br />R = rainfall factor, <br />K = soli erodibility factor, <br />LS = dimensionless length-slope factor, <br />C = cover factor, and <br />P = conservation practice factor. <br />For this assessment, two of the USLE parameters are variable. The primary <br />variable is the cover factor, C, which takes on different values as the <br />characteristics of vegetation changes. Mining will change the slope <br />characteristics, so LS will be variable in comparing the existing condition to <br />the three (3) reclamation conditions. The other parameters - R, K and P will <br />remain constant for each condition. Their values are: <br />R = 75 This value derives from Figure 1, SCS Technical <br />Note 50 (1984). <br />K = 0.17 This value derives from the soil characteristics <br />of the area. The SCS Soil Survey of El Paso <br />County (SCS, 1981, p. 203) identifies this value <br />as 0.17 taken from a Paunsaugunt series soil. <br />P = 1.0 There will be no differences in planting or <br />conservation measures between conditions so this <br />value is constant at 1. <br />