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• gradients, and anticipated refuse thickness as listed below: <br /> Waste Liner Footprint <br /> Development Area Thickness Gradient Area <br /> Ft. % Acres <br /> Intermediate Liner <br /> Area (existing Austin 90 5 75 <br /> Road Landfill <br /> New (existing <br /> undeveloped Forward 80 3 117 <br /> Landfill) Area <br /> New (existing <br /> undeveloped Austin 190 2 33 <br /> Road) Area <br /> Phase 10 (south of <br /> existing Forward 100 2 23 <br /> Landfill <br /> The HELP simulations were run for a period of 30 years; 20 years of active refuse <br /> disposal, and 10 years of the post-closure period with final cover and no positive <br /> or negative flux through the landfill's geomembrane cover. The simulations <br /> • conservatively ignored placement of intermediate cover soils, and assumed that <br /> a one-foot thick LCRS drainage layer would be placed at a 2% gradient on top of <br /> a geomembrane layer at the base of refuse. LCRS collection pipe was assumed <br /> to exist on 200-foot centers. <br /> Model Results <br /> As shown below, the peak daily leachate that is calculated to be generated in the <br /> HELP analyses is approximately 0.027 inches. As shown in the graphs included <br /> in Appendix D, this occurs within five years of refuse placement with periodic <br /> spikes that follow and which may be related to variable annual rainfall. Within a <br /> one-acre landfill area, the peak daily leachate generation amounts to <br /> approximately 4,073 gallons or approximately 0.006 cubic feet per second (cfs). <br /> The peak daily head on the liner system was calculated to be approximately 1.6 <br /> inches Accordingly, the 200-foot spacing of the LCRS appears more than <br /> adequate to keep less than one-foot of leachate head on the liner. <br /> • <br /> Forward Landfill JTD 5-23 <br /> L:\Allied\2000.193\Reports\td:Sec-5.0:05/24/02 <br /> BRYAN A.STIRRAT&ASSOCIATES <br />