Laserfiche WebLink
the downgradient silt fences to limit downgradient flow of <br /> sediment-laden water. <br /> As the attached flood insurance map (Drawing 6) indicates, the <br /> Foothill Sanitary Landfill site is not in the 100 year flood <br /> plain. <br /> SLOPE PROTECTION AND EROSION CONTROL <br /> Slope protection and erosion control will be mainly by vegetating <br /> and keeping slopes at or below a maximum of 3 : 1. The 3 : 1 slopes <br /> will be along the perimeter of the landfilled area. The other <br /> final cover slopes will be 2-6% to prevent drainage slope <br /> reversal from landfill settlement. The 2-6% slopes will also <br /> keep sheet flow on the landfill surface at minimal eroding <br /> velocities. <br /> The entire final site face will be vegetated with drought <br /> resistant grass to provide a low maintenance form of erosion <br /> control. The grass will be fertilized as needed and it will not <br /> require irrigation. <br /> Silt fencing may be constructed along the steeper toe slopes <br /> parallel to the drainage ditches to prevent soil from being <br /> washed into the drainage ditches. The design details for the <br /> sediment and erosion control features will be shown in the <br /> landfill construction drawings. <br /> A run-off analysis is included in this report as Appendix D to <br /> determine the potential sediment load that might run-off the <br /> site. An empirical method using the Universal soil loss equation <br /> was used to calculate the soil loss. The allowable sediment <br /> loss load was established to be 2 ton/Acre/year per the EPA <br /> Guideline Manual For Landfill Design Liner Systems and Final <br /> Cover document dated July 1982. The Sediment Load computed in <br /> Appendix D for the site is 0. 95 ton/acre/year. Since the <br /> sediment load is within the allowable loads, sediment load run- <br /> off is not considered a run-off problem. Additionally, the <br /> County will construct silting basins along the landfill's <br /> perimeter in order to capture this sediment load. These basins <br /> are shown on Drawing 2 of this Preliminary Closure Plan. It is <br /> anticipated that the 447, or so, cubic yards of sediment <br /> deposited in the site drainage system would be removed as a <br /> normal course of annual maintenance of drainage ditch grading. <br /> LEACHATE CONTROL <br /> A leachate collection and removal system will be installed as <br /> each module is excavated. A High Density Polyethylene (HDPE) <br /> 40 liner, leachate collection system, and a geonet will be installed <br /> 15 <br />