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Detectable concentrations of TPH-g in the samples ranged from 85 µg/L (MW5) to 170,000µg/L (V2) Benzene concentrations ranged from 5 3 µg/L (P2) to 12,000µg/L (V2) The concentration of TPH-g in the sample collected from MW8, located adjacent to the Shell service station and upgradient of the site, was 52,000 µg/L Groundwater sample analytical results are indicated in Figure 1 Petroleum hydrocarbon concentrations in the extracted soil vapor have decreased significantly since the start-up of the vapor extraction and treatment (VET) system at the site As can be seen in Figure 4, the monthly monitoring of TPH-g concentration in the extracted soil vapor entering the VET system oxidizer indicates a decline of one order of magnitude since start-up The monthly monitoring of benzene concentration in the extracted soil vapor entering the VET system oxidizer indicates a more drastic decline of two orders of magnitude since start-up, as can be seen in Figure 5 During the current quarter, petroleum hydrocarbon concentrations in the extracted soil vapor entering the VET system oxidizer have remained in the ranges observed during the previous quarter 2.1 WSPA STUDY Exxon RS 7-3942 is included in the Western States Petroleum Association (WSPA) Purging Study and was therefore sampled in October 1995 instead of November 1995 The site will be sampled one more time as part of the WSPA study, in January 1996 The normal sampling rschedule will resume the following quarter !� The WSPA study is being conducted to assess the significance of purging in obtaining representative samples of groundwater Both pre-purge and post-purge samples are collected from selected groundwater monitoring wells, following a WSPA-approved protocol prepared by SECOR International, to determine if there is a statistically significant difference in hydrocarbon concentrations between pre-purge and post-purge samples The analytical results provided in this report are from post-purge samples Analytical results for pre-purge samples are provided in the laboratory report, but are not included in this quarterly report Laboratory analytical results and chain-of-custody documentation are provided in Appendix B 3. WORK PROPOSED FOR NEXT QUARTER Groundwater elevations will be measured, and groundwater samples will be collected in January 1996 The samples will be analyzed for TPH-g, BTEX, and MTBE The soil vapor extraction and air sparging system will continue to be operated and its progress monitored WP61 73942Q1095 3 2