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SOIL ERODIBILITY FACTOR (K) <br />• The soil erodibility factor K is a measure of a soil's susceptibility to erosion and was <br />determined from the regional soil survey (SCS, 1981). From the soil survey maps, ii <br />was determined that the Fughes Loam soil series is present in the Lone Pine Gulch <br />Surface Facilities Area, and the Absarokee-Work soil association is present at the <br />Water Tank Site. <br />For the purposes of our analysis, a K factor of 0.26 was selected for use in analyzing <br />the Underground Development Waste Pile, as Fughes loam topsoil has been replaced <br />and revegetated on the pile. For the adjacent Topsoil Pile, a K factor value of 0.26 <br />was also selected, as the topsoil salvaged in this area corresponds to the "A" horizon of <br />the Fughes loam series soil. A K factor value of 0.32 was selected for use in analyzing <br />the Staging Area, as the surface exposed to erosion in this area is comprised of Fughes <br />loam subsoil. For the adjacent undisturbed oakbrush vegetation community, a K factor <br />value of 0.2 was selected, reflecting the undisturbed nature of the "O" and "A" <br />horizons of the Fughes loam. <br />A K factor value of 0.35 was selected for use in analyzing the Water Tank Site. This <br />value represents an average of the K factor values for the subsoils of the Absarokee and <br />Work soil series. The K factor value selected for the adjacent undisturbed area is 0.37, <br />representing the table value of the "A" horizon for both the Absarokee and Work soils. <br />• LENGTH SLOPE FACTOR (LS) <br />The steepness of the slope and the length of the slope both affect the degree of soil <br />erosion on a given slope surface. The LS factor is a ratio of soil loss at any length and <br />slope to that of a standard empirical slope. For the areas to be evaluated at the West <br />Elk Mine, the reclaimed and adjacent undisturbed slopes are of relatively uniform slope <br />for the areas of concern. In this case the LS factor can be calculated by the following <br />equation: <br />LS = (), / 72.6)m * (430x'- +30x + 0.43)/6.613 <br />where: <br />~ is slope length <br />x is sin B (where B is the angle of slope) <br />m is a slope dependent exponent (0.5 in our case) <br />LS factors for the areas to be evaluated were calculated based on measurements drawn <br />from Map 53A (Lone Pine Gulch Surface Facilities Distribution) and Attachment 1 <br />(Water Tank Site) (Figures I and 2). For each reclaimed or revegetated area, an <br />• average slope angle was determined from the map. Slope length for the reclaimed or <br />revegetated areas was determined from the longest slope length within the reclaimed <br />-3- <br />