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approximately 40 feet wide by 500 feet long. The number of operating LTUs at <br /> any given time will vary according to the market need for the soil treatment <br /> process. Previously constructed LTUs have consisted of a 40-mil polyvinyl chloride <br /> (PVC) liner covered with a 6-inch-minimum thickness layer of sand and gravel, an <br /> 18-inch minimum thickness layer of compacted clay, and a 6-inch-minimum <br /> thickness layer of a sand and gravel buffer zone. A layer of contaminated soil <br /> approximately 18 inches thick is placed within each LTU for treatment. <br /> Berms contain stormwater within the LTUs, and a drainage system removes storm- <br /> water that accumulates. The surfaces of the LTUs will be sloped so that excess <br /> rainwater drains to a storage tank. Water stored in the tank will be used for soil <br /> moisture control during the treatment process or pumped to the leachate <br /> evaporation pond. <br /> A monitoring system has been designed to test the soils to ensure the efficiency of <br /> hydrocarbon biodegradation. Soils in the LTUs will be sampled regularly to <br /> evaluate and manage the key treatment parameters such as soil moisture, soil pH, <br /> soil nutrient levels, and air temperature. Following treatment, the soil will be <br /> analyzed to determine if the petroleum hydrocarbon concentration meets the level <br /> acceptable for use as alternative cover or foundation material, or disposal. <br /> Each LTU will have a lysimeter at the low point for leak detection. The lysimeters <br /> monitor moisture in the vadose zone directly beneath the drainage system and are <br /> checked on a quarterly basis. <br /> These treatment units may also be used to treat other nonvolatile organics that are <br /> suitable for bioremediation such as PNAs. <br /> Treatment of Gasoline Contaminated Soil <br /> The "Preliminary Soil Remediation Work Plan, Gasoline Contaminated Soil, <br /> Forward Landfill Unit WMU G, Stockton, California" (Harding Lawson Associates, <br /> July 1991) describes the treatment system for gasoline contaminated soils. The <br /> specifications and reporting requirements of the treatment system are specified in <br /> the WDRs, Order No. 97-141 and in an October 31, 1990, letter from SJCPHS to <br /> Forward. <br /> Forward Landfill JTD 6-15 <br /> J.\Allied\Forward\ITD Amendment\Final JTD Amendment\JTD Sec 6 080105.doc:5/22/02 <br /> Rev.1:7/2002:Rev.2:4/2003;Rev 3:6/2003 BRYAN A.STIRRAT 6 ASSOCIATES <br /> Amendment No.1:8/1/2005 <br />