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. Site History Canepa's Car Wash(Pacific Avenue) Page 4 of 7 the study area. No apparent actively pumped drinking water wells were located within 500 feet of the site, however. Condor performed additional groundwater investigation activities at the site consisting of three CPT borings, hydropunch sampling, and the installation of three soil borings and four monitor wells. Details of the investigation are presented in the Additional Soil and Groundwater Investigation Report dated January 21, 2002. Twelve monitor wells, MW-I through MW-12d, were surveyed as part of the investigation. The new survey identified errors in the previously reported elevations of monitor wells MW-6 and MW-7. The new survey elevations for these wells are higher than previously reported, and consequently, the groundwater elevation contours for the site no longer indicate a groundwater mound in the vicinity of monitor well MW-2. The task of surveying the monitor wells was sufficient to complete the Groundwater Monitoring Sturdy Report dated February 13, 2002. Condor performed quarterly monitoring activities at the site on January 10, 2002. Laboratory analytical results of the groundwater samples indicated concentrations of petroleum hydrocarbon constituents that were consistent with historical data. The analytical results also indicated substantial declines in contaminant concentrations in monitor wells MW-1 I and MW-12d compared to the initial laboratory analytical data collected from these wells in October 2001. The SVE system, modified to utilize two 1,000 pound vapor phase carbon vessels connected in series, was restarted on March 13, 2002. Vapor samples from the influent and mid tank locations were collected in Tedlar bags and submitted for laboratory analysis of BTEX constituents. The system influent and effluent soil vapor flow rates and influent, mid tank and effluent soil vapor concentrations are measured weekly using a pitot tube and photoionization detector (PID), respectively. Sol] vapor samples from the influent, mid tank and effluent sample ports for laboratory analysis are collected quarterly. Condor performed quarterly monitoring activities at the site on April 4, 2002. Laboratory analytical results of the groundwater samples indicated concentrations of petroleum hydrocarbon constituents that were consistent with historical data with the exception that concentrations of BTEX constituents generally declined in monitor well MW-2, and low concentrations of benzene and TPH-G were detected in well MW-4. The analytical results also indicated declines in contaminant concentrations in monitor wells MW- 11 and MW-12d compared to the initial laboratory analytical data collected from these wells in October 2001. The SVE System was sampled for laboratory analysis on June 11, 2002. The concentration of the soil vapor was estimated using a correction factor derived from the results of the laboratory analytical results of soil vapor samples collected on June 11, 2002 and the concurrent PID measurements. The PID measured soil vapor concentration multiplied by a correction factor of 0.84 provides an estimate of the soil vapor concentration as TPH-G. During the June SVE sampling event, the mid tank soil vapor sample indicated concentrations of BTEX constituents, TPH-G and MTBE below the laboratory reporting limit, and therefore the destruction efficiency of the SVE system was estimated at 100%. Condor performed quarterly monitoring activities at the site on July 1,2, and 3, 2002. Laboratory analytical results for the groundwater samples collected from the monitoring wells were generally consistent with historical results. The SVE well groundwater analytical results were generally consistent . with historical results, except the BTEX concentrations detected in samples collected from SV-I and SV- 9 were lower and the MTBE concentrations detected in samples collected from SV-4 and SV-9 were