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3.6.2 SOIL LOSS ANALYSIS <br /> The Universal Soil Loss Equation (LISLE) was used to evaluate potential soil losses <br /> within the watershed boundary of the Forward Landfill site. The USLE was <br /> initially intended for analysis of meadows and cropland soil loss. However, with <br /> certain engineered assumptions, it can be applied to soil cover over landfills. <br /> The USLE is: <br /> A = RKLSCP <br /> where A = average soil loss, in tons/acre <br /> R = rainfall and run-off erosivity index <br /> K = soil erodibility factor, tons/acre <br /> L = slope-length factor <br /> S = slope-steepness factor <br /> C = cover-management factor <br /> P = practice factor <br /> The soil loss analysis performed is based on a "closed landfill' condition as <br /> required by CCR Title 27, and for a post final closure construction condition to <br /> estimate sediment amounts as a basis for sizing the sedimentation basins. At <br /> closure, the potential soil loss is minimal because the landfill will have a <br /> compacted final cover, an erosion control surface of vegetation and a storm <br /> drain system installed which all contribute to controlling soil erosion. The landfill <br /> soil loss analysis data is presented in Appendix F. <br /> The following USLE constants were utilized for the "closed landfill" condition: <br /> R = 20.41 Average annual rainfall value <br /> K = 0.28 Soil erodibility <br /> 3.20 < LS < 5.90 Dependent upon length gradient <br /> C = 0.05 Based on vegetative material <br /> P = 0.10 Practice factor <br /> For the purpose of the soil loss analysis, the landfill was divided into regions <br /> based upon the average slopes of the final grades and surface drainage (Drawing <br /> Sheets 2 through 7). The "closed landfill" average soil loss for Stage IA of the <br /> Forward Landfill is 0.15 tons/acre/year which is below the two tons/acre/year <br /> allowed by the CIWMB. Over the 30-year post-closure maintenance period, the <br /> average soil loss over the entire Stage IA partial closure area will be <br /> approximately 0.03 inches. The 30-year soil loss represents 0.1 percent of the <br /> Forward Landfill PFCPCMP 3-12 <br /> J:\Allied\Forward\2005.0051 Partial Closure\Partial Closure Plan\FL-secIdoc:6/15/2005 <br />