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T , Unocal Service Station #6981 February 1, 1995 CURRENT QUARTER'S ACTIVITIES Field activities conducted at the subject site during the fourth quarter 1994 included monitoring and sampling of the groundwater monitoring wells by MPDS Inc of Concord, California, bi-weekly monitoring of VES operational parameters by Gettler-Ryan Inc (G-R) of Dublin, California, and monthly sampling of the VES influent and effluent vapor stream by G-R VES sampling procedures are presented in Appendix A. Monitoring and Sgmpling of Qroundwater Monitoring Wells Groundwater monitoring wells were monitored and sampled by MPDS on October 26 and 27, 1994 Based on measurements collected by MPDS, the groundwater beneath the site appears to flow toward the northeast an approximate gradient of 0 006 Total Petroleum Hydrocarbons as Gasoline (TPI-1g) were detected in groundwater samples from wells MW-1, MW-3 through MW-5, and MW-7 at concentrations ranging from 6 8 to 24,000 parts per billion (ppb) Benzene was detected these same wells at concentrations ranging from 4 0 to 11,000 ppb A copy of the MPDS Quarterly Data Report is presented in Appendix B Momtonng and S Wiling of VES, The VES consists of six vapor wells (VW-1 through VW-6) manifolded into a single vapor stream connected to a Baker Furnace thermal/catalytic oxidizer system After destruction of the extracted petroleum hydrocarbons, the vapor stream is discharged to the atmosphere The system operates under San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD) Permit To Operate Number N-3335-1-0 Schematic representation of the VES is shown on the Process Flow Diagram (Figure 3) A copy of the SJVUAPCD permit is presented in Appendix C The VES parameters were recorded every two weeks and vapor samples collected monthly during the fourth quarter 1994 G-R collected samples from the VES influent and effluent vapor streams on October 7, November S, and December 11, 1994 VES field monitoring data are summarized in Table I The calculated influent flow rate from the wellfield ranged from 62 9 to 154 8 standard cubic feet per minute (scfm), and the calculated effluent flow rate ranged from 138 6 to 292 4 scfm Collected vapor stream samples were submitted to the Sequoia Analytical laboratory located in Redwood City and Sacramento, California (FLAP #1210 and #1624, respectively) Samples were analyzed for TPHg and Benzene, Toluene, Ethylbenzene, and Total Xylenes (BTEX) by EPA Methods 5030180151$020 Chemical analytical results for 4855702-2 2 GeoStrategies Inc.