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0 The following USLE constants were utilized for the "closed landfill" condition: <br />R = <br />20.41 <br />Average annual rainfall value <br />K = <br />0.28 <br />Soil erodibility <br />3.20 <br />< LS < <br />Dependent upon length gradient <br />5.90 <br />C = <br />0.05 <br />Based on vegetative material <br />P = <br />0.10 <br />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 <br />(Drawing Sheets 2 through 7). The "closed landfill' average soil loss for <br />Stage IA of the Forward Landfill is 0.15 tons/acre/year which is below the two <br />tons/acre/year allowed by the CIWMB. Over the 30 -year post -closure <br />maintenance period, the average soil loss over the entire Stage IA partial <br />closure area will be approximately 0.03 inches. The 30 -year soil loss <br />represents 0.1 percent of the total final cover thickness. This analysis <br />assumes a seventy to eighty percent ground cover of the specified vegetation <br />will exist over the post -closure period. <br />0 3.6.3 EROSION CONTROL <br />The Stage IA partial closure design has two primary erosion control features <br />that will reduce the potential for soil erosion due to water and wind. These <br />features include vegetation and a slope bench system. <br />The slope bench will be constructed at approximately a 50 -foot vertical <br />interval along the landfill slope. The final slope bench system and a series of <br />downdrains will reduce the length of travel of run-off on the slope face thus <br />reducing the potential for erosion rills and gullies. <br />The landfill surface will be vegetated with native grasses as shown on <br />Drawing Sheet 9. The vegetation will protect the upper soil layer and <br />minimize erosion through the vegetation root masses. Table 4 presents the <br />seed mix. Additional erosion control measures will be utilized including a silt <br />fence at the toe of slope, wattles (fiber rolls) and silt fences at the inlets as <br />shown on Drawing Sheet 9 and detailed on Drawing Sheet D-4. <br />Forward Landfill PFCPCMP 3-13 <br />Z:\PROJECTSWIIied Waste\Forward\Reference Files Prior JTD\June 05 Stage IA Partial FCPCMP\FL-sec3.doc: 6/16/2008 <br />