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Third Quarter,2002 Quarterly Groundwater Monitoring Report Canepa's Car Wash,Pacific Avenue,Stockton,CA Page 4 • SOIL VAPOR EXTRACTION SYSTEM The soil vapor extraction (SVE) system, modified to utilize two 1,000 pound vapor phase carbon vessels connected in series, was started 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, TPH- G and MTBE. Analytical results of the vapor samples are included in Table 3, below and in Appendix E. The system influent and effluent soil vapor flow rates and influent, mid tank and effluent soil vapor concentrations are measured weekly using a picot tube and photoionization detector (PID), respectively. Sail vapor samples from the influent, mid tank and effluent sample ports for laboratory analysis are collected quarterly. The SVE system monitoring form is included in Appendix D. The concentration of the soil vapor can be 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%. Table 3 SVE System Vapor Sample Laboratory Analytical Results June 11,2002 Date Sample ID benzene I toluene eth l benzene xylenes MTBE 'ETPH-G PID(ppm)] 6/11/2002 1707B-inlet-6/11/02 <0,15 <0.15 0.33 4.0 <1.5 43 56.3 • 6/11/2002 1707B-midtanks-6/11/02 <0A5 <0.15 <0.15 <0,15 <1.5 <15 0 6/11/2002 170713-exhaust-6/11/02 <0.15 <0.15 <0.15 <0.15 <1.5 <15 0 Note:Air matrix units are reported as ppmv(IAL/I.,). PID=Photo ionization detector. NA=Not analyzed. PPM=Parts per million. FUTURE WORK/ RECOMMENDATIONS The SJCEHD has indicated that quarterly groundwater monitoring continue at the site. In a letter dated July 30, 2002, Condor requested temporary shut-down 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 site planned by the property owner. The SJCEHD and Condor have agreed, however, that the SVE unit will be operated until the moving the system is imminent. Condor is currently preparing a Problem Assessment Report (PAR) and a Corrective Action Plan (CAP) for the site to be submitted under separate cover. Following submittal of the PAR and CAP and approval of a comprehensive remedial approach for the site, the SVE unit will be restarted in an enhanced mode. The next quarterly groundwater monitoring event is scheduled for October 2002. • 's 4M IL l' CONDOR