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inches in diameter. IAS wells will extend to the bottom of the saturated section of Corcoran Clay, while VES wells will terminate about 5 feet above the highest groundwater elevation measured in the last five years. In order to operate efficiently, in-situ air sparging systems (IAS) commonly require an air flow of 10 to 20 cubic feet per minute (cfm) per well, at 1 to 3 times the "breakout pressure". The breakout pressure (bp) is defined as the depth of the sparge injection point below the static groundwater surface divided by 2.3. Assuming an average aquifer thickness of 25 feet and using a by multiplication factor of 1.7, the pressure that will be required within the IAS wells is 18 psi. As is typical for IAS systems, air will be injected into the bottom of the aquifer through a screen section that is 1-2 feet in length using a 30 horsepower (hp), 150 cfm compressor. VES wells will be required to effectively direct and control the injected air rising from groundwater to the vadose zone. To ensure complete capture of the injected sparge air, the VES wells will be positioned between the IAS wells, and the operating air flow that is pulled from the VES wells will be about 4 to 5 times the injection air flow rate (about 60 to 100 cfm in this case), at 5 inches of vacuum. Vapor extraction will be powered by a 50 hp, 750 cfm blower. Extracted vapors will be discharged to the landfill gas collection system for destruction in the flare. Owing to the depths that air must be injected and the length of treatment along the point-of compliance that must be treated, the IAS/VES system will likely have relatively high air flow requirements that will necessitate multiple compressor/blower systems. In order to establish a modular design that accommodates increasing or decreasing the area of treatment, the conceptual design for the IAS/VES system includes 4 compressor/blower stations, each of which control 10 IAS wells and 10 VES wells. Based on the air flow requirements specified above, each station will have a compressor ([AS system) with a maximum capacity of 300 cfm at 20 psi and a blower (VES system) with a capacity of up to 1000 cfm at 5 psi. Capital costs for installation of the system are approximately $1,386,720 (Table 1013), with annual 0&M costs of approximately$482,693 (Table 10C). 4.4 NO. 4: INTRINSIC REMEDIATION As described by Weidemeier et al (1999), intrinsic remediation refers to naturally occurring processes in soil and groundwater environments that act to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in those media. In practice, intrinsic remediation approaches typically also involve measures to monitor and control the source of Engineering Feasibility Study Geo-�og0c Page ■ 24 Corral Hollow Sanitary Landfill ASSOCIATES January 25,2013