SITE INFORMATION AND CORRESPONDENCE

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• �./ San Joaquin fey Air Pollution Control District Page 6 PROPOSED VAPOR EXTRACTION SYSTEM The proposed soil vapor extraction system will initially extract hydrocarbon vapors from two wells installed within the former UST pit. Vapor well VWl is screened from approximately 55-70 feet bgs, and vapor well V W2 will be screened from approximately 22-47 feet bgs. Subsequently, an existing groundwater extraction well (EW I) and up to two additional groundwater monitoring wells (MW3, MW4) may be added to the system, at which time the system will become a dual phase extraction system. Groundwater extraction well EW1 is screened from approximately 60-80 feet bgs, well MW3 is screened from approximately 56-76 feet bgs, and well MW4 is screened from approximately 55-75 feet bgs. Groundwater beneath the site currently exists at approximately 70- 71 feet bgs. A 25-horsepower liquid-ring blower will extract the vapors (and groundwater) through subsurface PVC collection piping to the remediation compound where the vapors will be treated by thermal oxidation prior to discharge through a stack. The water and vapor will be separated within an entrained liquid separator. Separated water will be routed through an air stripper currently in operation at the site. The air stripper currently produces less than 0.5 lb/day of emissions and thus requires no permit from the APCD. Once the influent concentrations are sufficiently reduced, the unit will be converted to catalytic oxidizer for off-gas treatment. The locations of the wells, remediation compound and subsurface piping are shown on Figure 3. The Process Flow Diagram for the proposed abatement equipment for treatment of extracted petroleum hydrocarbon vapors/water is shown on Figure 4. Process equipment will be located in the remediation compound and includes a liquid separator, a vacuum blower, and a thermal/catalytic oxidation system with associated controls and instrumentation. The system will include ports for sampling both influent and effluent vapors, instrumentation for measuring and recording temperature, flow and hours of operation. The design flow for vapor extraction is 50 scfm at a design wellhead vacuum of 50 inches of eater, based upon the vapor extraction test. However, in anticipation of increased vacuum and flow due to the liquid ring pump as well as the extraction of groundwater in the future and the possibility of installing additional wells, the permitting application and associated forms have been filled out for design flow between 200 efm and 400 cfin. INFLUENT AND OFF-GAS EMISSIONS RATE CALCULATIONS The selected vapor extraction system/emissions control device is a dual-phase extraction system, which utilizes a 25 hp, liquid-ring blower and a thermal/catalytic oxidizer with a maximum capacity of 400 cfrri. Although the results of the vapor extraction system suggests that the flow rate would be much lower, the test was conducted using an IC Engine, which may not give a fair representation of actual attainable flow rates. In addition, groundwater remediation conducted subsequent to the vapor extraction test has apparently removed free product and significantly lowered contaminant concentrations in the groundwater. Therefore, we have made additional calculations of potential removal`and off-gas emissions rate calculation based upon the maximum Zn G:IGROUNDZE-'.TULEBURG\Vapor Extraction permits\VEScvrltr.DOC