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1 4 August 1995 AGE-NC-95-0120 Page 4 of 5 ' 4 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-g was detected in samples collected in March 1995 from MW-2 and MW-3 at concentrations of 64 ppb and 130 ppb, respectively Benzene was detected in all wells at the site in March 1995 at at concentrations up to 0 94 ppb,toluene was detected in MW-1 and MW-2 at concentrations of 0 35 ppb and 0.37 ppb, respectively No TPH-d, ethyl benzene or xylenes were detected in samples collected in March 1995 The analytical results of the ground water samples are included in Table 2 The laboratory report and chain-of-custody are included in Appendix B ' Benzene was detected in the sample collected from MW-2 in June 1995 at a concentration of 0 4 ppb No TPH-g, TPH-g, toluene, ethyl benzene or xylenes were detected in water samples collected in t June The analytical results of the samples are summarized on Table 2 The laboratory report and chain-of-custody are included in Appendix C ' 5.0. CONCLUSIONS & RECOMMENDATIONS TPH-g was reported in monitoring wells MW-2 and MW-3 and benzene was detected in all wells during the March 1995 monitoring event However, only a trace concentration of benzene was detected in MW-2 during the June 1995 monitoring No other petroleum hydrocarbons were detected ' dunng the June 1995 sampling Although little or no hydrocarbons were detected during the first and second quarters of 1995, it is ' likely that the PHS EHD will require the installation of additional ground water monitoring wells at the site, as recommended by GeoAudit in previous reports Additionally, AGE recommends the installation of a vapor extraction well near the center of the former UST excavation, where ' hydrocarbon-impacted soil is present at depths below 30 feet The well should be used for the performance of a pilot test assessing the feasibility of soil vapor extraction at the site It is our understanding that Park Environmental, consultant for USA Gasoline, will be installing three _ additional monitoring wells in the area during the third quarter of 1995 At least one of these wells should provide"up-gradient" data for the Pacific Gas site Arrangements should-be made to utilize ' data collected from one or more of the USA Gasoline wells in conjunction with additional wells at the Pacific Gas site 6.0. LIMITATIONS Our professional services were performed using that degree of care and skill ordinarily exercised by environmental consultants practicing in this or similar localities The findings were based upon analytical results provided by an undependent laboratory -Evaluations of the geologic/hydrogeologic