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w REMEDIAL ACTION PLAN USA STATION#65 - LODI NOVEMBER, 1995 7.0 VAPOR EXTRACTION SYSTEM INSTALLATION AND OPERATION 7.1 VES Manifold and Vent Piping Park proposes to use existing wells MW-8, S-1 and S-2 as vapor extraction points. Park will connect the wells using 4-inch diameter, Schedule 40 PVC vent lines. The piping will be manifolded together at the treatment compound,which will be located on the eastern side of the carwash. Piping from the manifold to the catalytic oxidizer will also be 4-inch diameter, Schedule 40 PVC. The vent line from each well will be equipped with a ball valve and vacuum gauge for monitoring and controlling vacuum and passive air venting. The locations of the catalytic oxidation unit, the piping alignment and the extraction wells are shown on Figure 3. 7.2 250 SCFM "Bobcat" Catalytic Oxidization Unit and VES Manifold Piping i„ Installation Vapor extraction and catalytic destruction will be accomplished using a 250 cubic feet per minute +- (CFM) "Bobcat" catalytic oxidation unit, manufactured by Stealth Industries of Anaheim, California. The unit will be installed in the central portion of the site, on the northeast side of the carwash. The unit will be installed in this low- traffic area so that vapor extraction and treatment activities may be conducted with minor disruption to normal business operations. The "Bobcat" is all electric and uses heating coils in the combustion chamber as it's primary heat source. Since the vapor extraction system is only expected to operate for a few months a portable generator will `W be used as a temporary power source. ti. 7.3 Equipment Configuration Vapor extraction equipment for the site includes a vacuum pump connected to the extraction ` wells via PVC piping. This vacuum helps to volatilize the volatile organic compounds (VOCs), which may be adsorbed onto the surface of the soil grains or present in the pore spaces. In addition,the vacuum creates a pressure gradient towards the extraction wells, inducing air and the volatilized VOCs to flow through the soil and into the wells. The vapors are then pulled up the well and to the pump,where they are routed to the vapor treatment unit. As vapor extraction continues and as more air flows through the soil, VOC concentrations will decrease, both in the .� soil and the vapor stream. The "Bobcat" catalytic oxidation unit operates at a maximum of 25 percent of the lower explosive �- limit(LEL),which may initially necessitate extracting a limited amount of subsurface soil vapors and diluting the vapors with ambient air prior to treatment. Catalytic oxidation involves oxidizing the hydrocarbons to carbon dioxide and water by the burning of the vapor influent in the combustion chamber. The vapor flow is controlled by an automatic valve mechanism, which monitors the operation temperature within the combustion chamber and at the stack. 8 6-