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3.6.1.2 PROPOSED FINAL DRAINAGE CONTROL SYSTEM The proposed final drainage control system for the Forward Landfill Stage IA is shown on Drawing Sheets 3, 4, 5, 6 and 7. Runoff is directed to the natural drainage course. The proposed final drainage control system for Stage IA will include exterior slope AC downdrains, and topdeck drainage berms, deck inlets, bench drains and inlets. Runoff is directed to the natural drainage course. Stage IA drainage improvements will also include placement of additional soils along the perimeter road to increase the elevation of the road above historic and potential flood levels. Drainage details are presented in Drawing Sheets D-1, D-2, and D-3. 3.6.2 SOIL LOSS ANALYSIS The Universal Soil Loss Equation (USLE) was used to evaluate potential soil losses within the watershed boundary of the Forward Landfill site. The USLE was initially intended for analysis of meadows and cropland soil loss. However, with certain engineered assumptions, it can be applied to soil cover over landfills. The USLE is: A = RKLSCP where A = average soil loss, in tons/acre R = rainfall and run-off erosivity index K = soil erodibility factor, tons/acre L = slope-length factor S = slope-steepness factor C = cover-management factor P = practice factor The soil loss analysis performed is based on a "closed landfill' condition as required by CCR Title 27, and for a post final closure construction condition to estimate sediment amounts as a basis for sizing the sedimentation basins. At closure, the potential soil loss is minimal because the landfill will have a compacted final cover, an erosion control surface of vegetation and a storm drain system installed which all contribute to controlling soil erosion. The landfill soil loss analysis data is presented in Appendix F. Forward Landfill PFCPCMP 3-12 Z:\PROJECTS\Allied Waste\Forward\Reference Files Prior JTD\June 05 Stage IA Partial FCPCMP\FL-sec3.doc:6/16/2008