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5-4 <br />0 ♦ Drainage geocomposite; and <br />♦ A 12 -inch thick protective cover soil layer. <br />A drainage geocomposite collects leachate above the intermediate liner and transports <br />leachate downgradient to the base liner LCRS system, with eventual discharge to the lined <br />leachate ponds (i.e., evaporation impoundments). The intermediate liner detail is shown on <br />Drawing 6. <br />5.2.2.5 Surface Impoundment Units Liner System <br />Any new Class II surface impoundment will be constructed with the following liner system <br />components: <br />♦ Prepared subgrade of graded and compacted, native soil; <br />♦ A geosynthetic clay liner; <br />♦ A 60 -mil HDPE geomembrane; <br />♦ A geonet LCRS layer; and <br />♦ A 60 -mil HDPE geomembrane. <br />The LCRS and leachate monitoring program are discussed in Section 7.1. <br />0 5.2.3 Final Grading <br />C <br />The final grade configuration for the Forward Landfill will consist of top deck gradients of <br />3%or greater sloping toward top deck perimeter berms. The top deck berms will divert <br />surface flows to down drains. Landfill slope runoff is also directed to downdrains via <br />benches located at 50 -foot maximum vertical intervals. Slope ratios for all slopes, except <br />the north -facing slope of the landfill, are proposed at 3:1 (horizontal to vertical) or flatter. <br />As shown on the final grading plan (Drawing 3), the landfills are joined along the northern <br />boundary by a 7.5 -acre wedge area. The area directly north of WMU A is inactive because <br />WMU A is a closed hazardous waste cell. Refuse fill will not be placed over the existing <br />leachate risers for WMUs D-89 and D-93 at the landfill to maintain continued access to these <br />riser pipes and also to future leachate risers that will be constructed in this area. The wedge <br />area provides approximately 8 mcy of capacity. <br />The permitted maximum elevation of the Forward Landfill is approximately 200 feet amsl. This <br />grading configuration allows conformance with the height limit zoning plan contours for the <br />Stockton Municipal Airport (see Figure 2). <br />Forward Landfill SWT Engineering <br />Joint Technical Document - April 2014 <br />z:\projects\allied waste\forward\five year permit rvw 2013\jtd-5 yr pr 2013\text\sec 5_final.doc <br />