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' Using the well spacings described above, existing soli vapor extraction wells should be sufficient to remediate hydrocarbon-affected soils beneath the Site Six(6) existing wells (VW-1 through VW-6) will be utilized for remediation at the Site 7 13 Equipment Layout ' Vapor extraction equipment planned for the Site includes a vacuum pump connected to wells via PVC piping All extraction wells will be utilized concurrently during vapor extraction remediation, if ' possible Process gas will be conveyed from the SVE wells in 2-inch diameter Schedule 40 PVC pipe, which was previously installed in a pipe trench by Thrifty personnel Above-ground equipment associated with the proposed SVE system will be housed in an existing equipment enclosure which ' consists of a block wall located along the western edge of the property The location of equipment associated with the SVE system may be observed In Figure 18 ' Thermal oxidation involves oxidizing the hydrocarbons to carbon dioxide and water A thermal oxidation unit contains a reinforced, insulated thermal treatment chamber When hydrocarbon-laden process vapor(containing abundant oxygen)passes through the chamber and approaches the heating elements, oxidation readily occurs as igrution temperature is reached The vapor extraction unit is equipped with safety devices to ensure safe operation of the equipment ' and safe conditions for the public The unit is "fail-safe" in that in the event of any malfunction the unit shuts off and no vapors containing petroleum hydrocarbons are released In the event that soil vapors have an increase in.petroleum hydrocarbon concentrations,the unit automatically compensates by opening a dilution valve which reduces vapor concentrations by allowing ambient air to nux with the soil vapors In the event of malfunction of the thermal oxidizer, the unit will shut off electricity to the vapor extraction pumps and heating elements Under no circumstances will untreated soil vapors be vented to the atmosphere The treated vapors exiting the thermal oxidizer are monitored to ensure public safety from exposure or explosion The thermal oxidizer will be capable of treating the process gas with a destruction efficiency in excess of 95% No combustible materials are utilized in the treatment process or stored on-site, minimizing the risk of fire or explosion A process and instrumentation diagram for the proposed SVE system is included as Figure 17 7.2 Groundwater Pump and Treat Groundwater pump and treat remediation has three major purposes 1) extract groundwater from the contaminated subsurface areas, 2)transfer VOCs from the groundwater to the surface for treatment, ' and 3) modify subsurface groundwater flow patterns to inhibit contaminant migration off-site The 12-hour pilot test extracted approximately 2,840 gallons of groundwater and 4 67 pounds of gasoline were recovered from the groundwater during the extraction test ' The groundwater pump and treat process is a physical treatment technique for the removal and treatment of water-bearing zone VOCs Used in conjunction with soil vapor extraction, capillary A•11528I1 ASA 19 1