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Input Parameters <br /> Parameter Selection Criteria <br /> Precipitation Synthetically developed by HELP using <br /> average monthly rainfall data for Stockton, <br /> California. <br /> Evapotranspiration Default values for Sacramento, California. <br /> Run-off Runoff coefficient modified for"poor stand <br /> ofgrass", but not transpiration. <br /> Soil and refuse moisture storage capacity Upper zone always at Field-Ca acit <br /> Root zone depth No vegetation included. <br /> Surface sloe 3%surface gradient. <br /> Subsurface lateral drainage 2%o gradient with LCRS pipe at 200400t <br /> ,centers. <br /> Solar radiation Data for Fresno, California data synthetically <br /> modified by HELP for Stockton's longitude <br /> and latitude. <br /> With the exception of the iterative moisture contents described below, all soil <br /> and refuse parameters used"in mode1ing'the"Forward"Landfill LCRS are default <br /> values selected from the HELP program as typical for municipal solid waste <br /> landfills. Weather data was synthetically generated by the program for the <br /> Stockton area and corrected for-th-e.lati de.of.1he.Forward Landfill facility, <br /> yielding an average annual rainfall total of approximately 15.5 inches. <br /> As a conservative measure, the HELP modeling that was completed for the <br /> project anticipated that the subgrade (liner) gradient beneath all development <br /> areas would be 2% and that yearly thickness of refuse would no greater than 10 <br /> feet. While wastes that are initially placed in landfills are typically dry, with a <br /> moisture content that"is well below their field capacity (moisture holding; <br /> capacity), for the Forward Landfill leachate generation analyses, as a conservative <br /> measure it was assumed that the upper 10-foot refuse section each yearly <br /> simulation would exist at its field capacity. The moisture content for underlying <br /> refuse layers was manually specified for each yearly simulation based on the <br /> results that were calculated for the previous year. As additional conservative <br /> measures, runoff was assumed to be impeded by a "fair stand of grass" though, <br /> for simulating transpiration, a bare ground (daily cover) condition was assumed. <br /> Current estimates are that the expanded Forward Landfill may operate for <br /> approximately 20 years. During this period, the landfill is expected to be <br /> developed within four major areas that have differing footprint areas, subgrade <br /> Forward Landfill JTD 5-22 <br /> L:\AI lied\2000.193\Reports\finalj td:Sec-5.0:08/2 2/01 <br /> BRYAN A.STIRRAT 6 ASSOCIATES <br />