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%T CO A S S O C I A T E S I N C . 5.2 Design Specifications ' 5.2.1 Vapor Extraction System ' The proposed VES will utilize existing vapor extraction wells VEI, VE2 and VE3, and a new vapor extraction well, a vacuum blower, and a thermal oxidizer to address the hydrocarbon impacted soil. The VES will be operated under similar conditions as the vapor extraction pilot test ' (VET) to achieve a similar estimated radius of influence for each well. Based on the results of the VET, use of VEl, VE2 VE3, and the new vapor extraction well as vapor extraction points should provide sufficient radius of influence to address petroleum impacted soil from 30 to 70 feet bgs. A ' map showing the approximate radii of influence of VE2, VE3, and the new vapor extraction well is included as Figure 16. Based on the removal rates of petroleum hydrocarbons observed during the VET (estimated to be approximately 34 pounds per day per one well), thermal oxidation was selected as the method off- gas abatement. Removal rates will be the greatest during the fust several months of operating the system and will exceed the allowable emission limit without off-gas treatment. The thermal oxidizer will be used until the influent concentrations of petroleum hydrocarbons decrease sufficiently to use vapor phase granular activated carbon for off-gas treatment. When extraction rates decrease to less than the per day permitted by the San Joaquin Valley Air Pollution Control District (SJVAPCD), elimination of the off-gas treatment will be proposed if the system is still in operation. ' Subsurface piping will direct extracted vapor from the wells to a nearby remediation compound. ' Components of the VES located in the remediation compound will include the following: a vapor extraction blower that will extract vapor from the wells through the subgrade piping; a flow indicator that measures extracted airflow; a condensate separator to remove entrained droplets of moisture; a thermal oxidizing unit; associated piping, control valves, pressure gauges, flow meters, instrumentation and controls; and a contained remediation system to preclude public access. Based on ATC's experience at similar sites and the results of the pilot tests, a 200-250 cfin thermal oxidizer would be sufficient to operate the vapor extraction component of the system and remediate the off-gas. The vacuum blower on the unit would create a maximum vacuum of 16 inches of mercury and an airflow rate of 100 standard cubic feet per minute. The thermal oxidizer on the unit would operate at a temperature of approximately 1400 degrees Fahrenheit and have a destruction efficiency of 95%to 99%. A process and instrumentation diagram for the VES is shown on Figure 17. ' 5.2.2 Groundwater Air Sparging The proposed groundwater air sparge (AS) system will utilize three new air sparge wells and a compressor to address the hydrocarbon impacted groundwater. The AS system will be operated using individual wells in sequence with on-line vapor extraction wells to control migration of the ' groundwater plume. The wells will be constructed of 2-inch schedule 40 PVC and will be screened ' s:IenviromnentaII212911reports\irp,dm 6