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l <br /> ♦Y <br /> 30 March 1999 <br /> iAGE-NC Project No 96-217 <br /> Page 2 of 5 <br /> I hydrocarbons impacting soil along the ground water capillary fringe Analytical results of soil boring <br /> samples are summarized on Table 2 <br /> Since installation of the three monitoring wells,AGE has monitored ground water at the site on three <br /> occasions, including the monitoring event reported in this report Depth to ground water commonly <br /> ranges from 6 2 to 7 6 feet below the tops of the well casings Ground water flows toward the north- <br /> northwest THP-g was detected in all three monitoring wells, with a maximum concentration of <br /> 3,500 micrograms per liter(,ug/1) encountered All BTEX compounds were detected in ground water <br /> samples from all three wells at concentrations ranging from 3 0 4g/1 to 290 ,ug/1, the maximum <br /> benzene concentration was 1 I ug/l Analytical results from the second monitoring event showed that <br /> the concentrations of all analytes had decreased by at least one order of magnitude from the <br /> concentrations detected during the initial monitoring event Some BTEX compounds were not <br /> present at detectable concentrations MTBE was detected in all three water samples from the initial <br /> monitoring event by EPA Method 8020, but was not confirmed by analyzing the samples by EPA <br /> Method 8260, the maximum MTBE concentration detected was 16 µg/1 MTBE was not detected <br /> during the second monitoring event by either EPA Method 8020 or 8260 <br /> 3.0. PROCEDURES <br /> A quarterly ground water monitoring event was conducted on the subject property on 18 November <br /> 1998 The work was performed in accordance with San Joaquin County Public Health Services - <br /> Environmental Health Division (PHS-EHD) and Central Valley Regional Water Quality Contzol <br /> Board guidelines for investigation of underground storage tank (UST) sites <br /> 3 1 MONITORING WELL PURGE PROCEDURES <br /> A Solinst water level meter was used to measure the depth to ground water in each well relative to <br /> the tops of the well casings The ground water elevation in each well was determined from these <br /> data Ground water elevations are summarized in Table 3 <br /> After ground water depth measurements were collected, each monitoring well was purged using a <br /> two-stage submersible pump Approximately 4 gallons of water (minimum of 3 well volumes) were <br /> evacuated from monitoring wells MW-1 and MW-2 Due to poor well recharge, only 3 gallons of <br /> water were removed from monitoring well MW-3 Temperature,pH and conductivity were ineasuied <br /> at 2-gallon intervals (except for MW-3), using an ICM model 52200 water analyzer The measured <br /> ground water parameters are tabulated in Appendix A Purged water was contained in 55-gallon <br /> drums for temporary storage on-site <br /> Advanced GeoEmironinenlal, Inc <br />