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hour, 1,000-year storm event. A computer program developed by Advanced <br /> Engineering Software was used to compute the run-off. The hydrology study <br /> map indicating drainage sub-areas and discharge points and calculations for on <br /> site and off-site flows is presented on Drawing 10 of the JTD. A summary of the <br /> peak discharge rates are included in the hydrology study calculations included in <br /> Appendix G of the JTD. <br /> 3.6.1.2 PROPOSED FINAL DRAINAGE CONTROL SYSTEM <br /> The proposed final drainage control system for the Forward Landfill is shown on <br /> Drawing 9 of the JTD. The final surface area of the landfill decks will be graded <br /> at a minimum three percent gradient to prevent ponding and promote lateral <br /> runoff. <br /> The proposed final drainage control system will include exterior slope <br /> downdrains, engineered deck area gradients and drainage berms, deck inlets, <br /> bench drains and inlets, perimeter trapezoidal channels, and sedimentation <br /> basins. Drainage details are presented in Drawing 7 of the JTD. Some of the <br /> interim drainage control features may be utilized as part of the final drainage <br /> control system for the site. <br /> 3.6.2 SOIL LOSS ANALYSIS <br /> The Universal Soil Loss Equation (USLE) 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 /> Forward Landfill PCPCMP 3-9 <br /> L:\Allied\2000.193\Reports\FinaIPCPCMP:FL-sec3.doc:5/21/02 BRYAN A.STIRRAT is ASSOCIATES <br />