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,. 06 February 2001 AGE-NC Project No. 95-0118 Page 6 of 7 3.4. ANALYTICAL.RESULTS OF GROUND WATER SAMPLES 1 Water samples collected from the monitoring wells did not contain detectable concentrations of - TPH-g, BTEX or fuel additives. Analytical results of ground water samples are summarized in i Table 2. The laboratory report (MAI Lab ID 58415 to 58420), Quality Assurance and Quality Control (QA/QC)report and a chain-o#-custody form are included as Appendix E. t 4.0. CONCLUSIONS Based upon results of ground water monitoring well sampling, AGE concludes: • The ground water table elevation occurred within the monitoring wells screens intervals during the sampling event and therefore provided representative ground water samples. The ground water flow direction was similar to previous inferred flow directions (Figure 3). • The dissolved hydrocarbon concentrations have decreased to near or below laboratory 1 ~_ l method detection limits. This decrease is attributed to the vapor extraction and air sparging activities at the site. • Soil impacted with TPH and minor concentrations of toluene, ethyl benzene and total xylene appears to be limited to the'former UST release area(Figures 4, 5 and 6). The residual mass of TPH-g is estimated to be 5.1 kg. _I • During the past two months of soil vapor extraction, an estimated 15 gallons of petroleum as gasoline have been extracted. a - 5.0. RECOMMENDATIONS Based upon data collected at the site,AGE recommends: _i The site be considered for closure. It is unlikely that additional remediation (soil vapor extraction) at the site would result in a significant reduction of the hydrocarbon mass, and is not necessary to reduce any dissolved hydrocarbon mass. I • Upon closure certification, all monitoring, vapor and sparging wells associated with the site should be abandoned in accordance with San Joaquin County regulations. Advanced GeoEnvironmental,Inc. i