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r Z These data are summarized on Table 1 and shown on the chemical concentration map (Plate 2) . o Separate phase product was not present in Well RW-1A this quarter o Ground water samples collected from deep wells MW-12 through MW-14 did not contain detectable levels of TPPH, or oxygenate compounds Benzene was detected in Wells MW-12 and MW-13 at concentrations of 2 9 and 1 4 ppb, respectively o Ground water samples collected from the Caltrans irrigation well and the 5 domestic wells did not contain detectable levels of TPPH or benzene, with the exception of 4,800 ppb of TPPH in the 2468 Country Club Boulevard (CCB) Well ® MTBE (by EPA Method 8020) was detected in the Caltrans irrigation well, the 2452 CCB Well, and the 2468 CCB Well Downhole sample at concentrations of 38, 17, and 8 7 ppb, respectively However, the EPA Method 8260 analysis for MTBE performed on these wells found MTBE to be ND at a detection limit of <2 0 ppb The 2468 CCB Downhole ground water sample contained MTBE at a concentration of 80 ppb when analyzed by EPA Method 8260 These data are summarized on Table 2 Quarterly Sampling SGround water samples were analyzed for Total Purgeable Petroleum Hydrocarbons quantitated as gasoline (TPPH) according to EPA Method 8015 (Modified), and benzene, toluene, ethylbenzene, and xylenes (BTEX), and methyl-tertiary-butyl-ether (MTBE) according to EPA Method 8020, and oxygenate compounds according to EPA Method 8260 and EPA 8015 (Modified) Additionally, a duplicate sample and an equipment blank were prepared and analyzed for quality control purposes Field monitoring data and chemical analytical data are summarized in Tables 1 and 2 Blaine's ground water monitoring report is presented in Appendix A Conclusions The concentrations of petroleum hydrocarbons in ground water samples from the shallow wells at the subject site have generally decreased since the first quarter 1998 ground water monitoring event Benzene was detected in on-site deep Wells MW-12 and MW-13 for the first time this quarter MTBE was detected by EPA Method 8020 in some of the domestic water wells, but the EPA Method 8260 analysis performed on these samples did not confirm the presence of MTBE The EPA Method 8260 analysis is considered the definitive analysis for MTBE, whereas the EPA Method 8020 analysis can give false positive results for MTBE MTBE was detected in the 2468 CCB Well . this quarter, however all of the wells between the Shell site and this well did not contain MTBE 240-0783 2