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Cover Factor "C" <br />For rangeland and pastureland, the "C" factor is directly related to the percent of the <br />ground covered by vegetation and the type of vegetation that is present. Subsurface effects <br />such as root mass can also be considered. The type of vegetation is important because <br />herbaceous plants with a live cover of 25% will protect the soil much better than a site <br />that contains an equal cover but where the cover is primarily comprised of trees or shrubs. <br />Table 3 (from EPA 1977) shows the variation in "C" factors for varying range conditions. <br />From the 1987 study of the dryland pasture and irrigated pasture areas, the cover <br />breakdown is given below: <br />Pre-Mine Conditions <br />Irrigate Pasture - 1987 Cover Data <br />The irrigated pasture study area had 5 percent bare ground, 23 percent litter, 0.3 percent <br />annual forbs, 43 percent perennial grasses, and 29 percent perennial forbs for 72 percent <br />perennial live vegetation. Note: The irrigated pasture cover data was taken from the Coal <br />Mining Permit C-81-008: 2005-2006 Mid Term Review, which is based on the 1987 <br />baseline survey. <br />0.3% Annual Forbs <br />43% Perennial Grasses <br />29% Perennial Forbs <br />23% Litter <br />Ground Cover (cover that contacts the surface) = Annual forbs + Perennial Grasses + <br />Perennial Forbs + Litter <br />Ground Cover = 95.3% <br />Canopy Cover = None <br />Canopy Cover = 0% <br />Using Table 3 and a canopy of 0% and the "G" canopy type, the C factor can be <br />determined. The best "C" value for the pre-mine irrigated pasture is 0.003. <br />Post-Mine Conditions <br />Irrigated Pasture - 2008 Cover Data <br />The vegetation data is from the report 2008 Vegetation Sampling for Phase 2 Bond <br />Release: Irrigated Pasture and Dryland Pasture. <br />SL-12 29MARIl.wpd 22