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Canepa's Car Wash(Pacific Avenue) Problem Assessment Report and Corrective Action Plan Page 3 1� optimum pumping rate of 5 gpm with an effective radius of 140 feet. Aquifer permeability for a twenty-foot screen length was estimated at 126 gpd/ft2. Quarterly groundwater monitoring was conducted at the site by WHF from March 1994 through June 1995. Historical groundwater analytical data indicated elevated concentrations of TPH-G and BTEX in MW-1, MW-2,MW-6, and MW-7. Low concentrations of TPH-G and BTEX were detected in MW-3, MW-4, MW- 5, and MW-8. Condor has been conducting quarterly groundwater monitoring at the site since August 1996. The elevation of the water table has generally increased since quarterly monitoring began in March 1994. Analyses of groundwater samples collected from selected SVE wells (SVE-1, 2, 3, 5, 7, S, and 9) indicated that high concentrations of TPH-G, BTEX, and MTBE were present in the former location of the fuel dispenser islands. A site investigation at the Canepa's Car Wash facility was conducted by Condor on July 31, 1996. The investigation included a review of existing reports of investigations and an evaluation of the existing SVE system located at the site. The report of the results was titled Soil Vapor Extraction (SVE)System Evaluation, dated September 23, 1996. Using the soil analytical data available for the site, Condor estimated that the volume of hydrocarbons present in the soil beneath the site was approximately 13,000 pounds or 2,050- gallons (6.34 lbs/gal). Based on the results of the evaluation of the SVE system and site background data, Condor recommended that operation of the ICU be suspended because the system did not appear to meet APCD permit conditions (i.e., 95% destruction efficiency). Condor further recommended that a 150 SCFM catalytic oxidation unit(CAT-OX) be installed at the site to extract and treat the gasoline contamination in the vadose zone. The configuration of the existing SVE wells appeared to be sufficient to remove a majority of the remaining gasoline contaminants in the vadose zone. � . During the fall of 1997, an Authority to Construct permit was applied for with the APCD for the installation of an SVE system. Prior to granting approval of the installation of the SVE system,the Underground Storage Tank Clean-Up Fund indicated the need for additional investigation. Condor subsequently conducted the ' installation and sampling of two soil borings adjacent to the SVE well array. The investigation included soil vapor screening using the Simulprobe sampling device in soil vapor collection mode. The results of the additional investigation indicated that high levels of volatile organic compounds were present in the soil and in the soil vapor at the site. The findings of the investigation were reported in Report — Soil and IGroundwater Investigation, dated June 12, 1998. Operation of the SVE system was initiated on March 15, 1999. Initial concentrations of total volatile organics up to 2,000 ppm were reduced to approximately 100 ppm by February 2001. SVE operation was stopped on February 6,2001 as a result in a drop in the SVE efficiency below 95%. Minor modifications and repairs were made to the blower extraction system and the SVE was restarted on July 10, 2001. By July 27, ' 2001, it was determined that the restarted SVE system would not maintain 95%efficiency. It was determined that the catalytic oxidation unit was not designed to efficiently remove the lower concentrations of petroleum hydrocarbon vapors left in the soil. In a letter dated August 20, 2001, Condor proposed a carbon treatment unit to replace the catalytic oxidation unit. The SVE system was modified to utilize two 1,000 pound vapor phase carbon vessels connected in series, and restarted on March 13, 2002. The system influent and effluent soil vapor flow rates and influent, mid ttank and effluent soil vapor concentrations are measured weekly using a picot tube and photoionization detector (PID), respectively. Soil vapor samples from the influent, mid tank and effluent sample ports for laboratory analysis are collected quarterly. ttN• �� CONDOR