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_ Site History Canepa's Car Wash(Pacific Avenue) _ Page 4 of 10 dated January 21, 2002 Twelve monitoring wells, MW-1 through MW-12d, were surveyed as part of the investigation The new survey identified errors in the previously reported elevations of monitoring 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 monitoring well MW-2 The task of surveying the monitoring wells was sufficient to complete the Groundwater Monitoring-Study 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 monitoring-wells MW=l l=and MWAU 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 acid influent, mid tank and effluent soil vapor concentrations are measured weekly using a pitot tube and photoionization detector (PID), respectively Soil 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 monitoring 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 monitoring wells MW-I I 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-'multtplied-by-a-correcti on-factor-of-0 84,provtdes amestimate-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-1 and SV- 9 were lower and the MTBE_ concentrations detected in samples collected from SV-4 and SV-9 were much higher than previously detected The groundwater sample analytical results from well MW-12D continue to indicate a trend of lower contaminant concentrations since the initial sampling event for this well conducted on October 25, 2001 The laboratory analytical results indicate a trend of increasing MTBE concentration at MW-3 The SJCEHD has indicated that quarterly groundwater monitoring continue at the site In a letter dated July 30, 2002, Condor requested temporary shutdown of the SVE unit based on data that indicates dwindling influent concentrations and to allow its relocation as part of the additional development of the