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to accelerate biodegradation of hydrocarbons (bioremediation process). The objective of the treatment process is to biodegrade the hydrocarbons to levels appropriate for landfilling. After the contaminated soils have been adequately treated, the soil can be used for daily cover, intermediate cover, or foundation layer for the closure cap. If necessary, the treated soils can be disposed in a Class If or Class IIi WMU. Although there are currently no Land Treatment Units (LTUs) at the site, LTUs have been constructed in the past and may be utilized in the future. LTUs for contaminated soil are permitted within WMU G-North or G-South. The units are approximately 40 feet wide by 500 feet long... The number of operating LTUs at any given time will vary according to the market need for the soil treatment process. Previously constructed LTUs have consisted of a 40-mil polyvinyl chloride (PVC) liner covered with a 6-inch-minimum thickness layer of sand and gravel, an 18-inch minimum thickness layer of compacted clay, and a 6-inch-minimum thickness layer of a sand and gravel buffer zone. A layer of contaminated soil approximately 18 inches thick is placed within each LTU for treatment. Berms contain stormwater within the LTUs, and a drainage system removes storm- water that accumulates. The surfaces of the LTUs will be sloped so that excess rainwater drains to a storage tank. Water stored in the tank will be used for soil moisture control during the treatment process or pumped to the leachate evaporation pond. A monitoring system has been designed to test the soils to ensure the efficiency of hydrocarbon biodegradation. Soils in the LTUs will be sampled regularly to evaluate and manage the key treatment parameters such as soil moisture, soil pH, soil nutrient levels, and air temperature. Following treatment, the soil will be analyzed to determine if the petroleum hydrocarbon concentration meets the level acceptable for use as alternative cover or foundation material, or disposal. Each LTU will have a lysimeter at the low point for leak detection. The lysimeters monitor moisture in the vadose zone directly beneath the drainage system and are checked on a quarterly basis. These treatment units may also be used to treat other nonvolatile organics that are suitable for bioremediation such as PNAs. Forward Landfill JTD 6-15 J:\Allied\Forward\ITD Amendment\January2006 JTD Amendment\JTD Sec 6 012506 Accept.doc: 8 5/22/02;Rev. 1:7/2002:Rev.2:4/2003;Rev 3:6/2003;Amendment No.1: 1/26/2006 BRYAN A 6TIRRAT ASSOCIATES