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05 June 2001 ; • AGE-NC:Project-No. 95-0106 �i Page 3 of 5 . ; contoured ground water elevation data is shown on Figure 3.'Ground water elevation in MW4.has . been unusually high for.reasons,not currently understood. 4.2.. ANALYTICAL RESULTS OF GROUND WATER SAMPLES Petroleum hydrocarbons were detected in the ground water samples collected from monitoring wells I MW-1,MW-4 and MW-7;MW-1 is located slightly cross and down-gradient from the former UST excavation,-MW-4 is located further north in,the generally down-gradient direction and MW-7. is located cross gradient,east of the former UST location.TPH-g was detected at concentrations of 960' micrograms per liter.(ug/l), 4,100 µg11 and 300 µg/1, respectively, in samples from the three wells. Benzene was detected at 280µg/1 and 100 µg/l in samples from MWA and-MW-4 respectively: : Other volatile aromatic compounds were detected at concentrations of 41 µg/1 and 9.0 µg/l toluene, and 18µg/l and 88 µg/1 ethylbenzene and 31 µg/l"and 120 µg/l xylenes in samples from MW-1 and: MW-4, respectively. Other an'alytes were not:detected in the two samples. Neither TPH-g nor.BTEX cbmpbunds were detected in the ground water samples from monitoring, wells MW-2, MW-3, MW-5, MW-6 (upper) and MW-6 (lower). MTBE was not detected in any of l the ground water samples. Analytical results of ground water samples are summarized on Table 2. The laboratory report (MAIL Lab ID 67878 through 67885), QNQC and chain-of-custody are included in Appendix B. 5.0. SUMMARY AND CONCLUSIONS The'following conclusions were drawn from the results of the site investigation: • The•ground water was generally northward on 17 May 2001; and was calculated to range . �' g Y Y from'0.001 toward the north-northwest to,0.003 toward the north-northeast. :., ' Dissolved petroleum hydrocarbons were detected in ground water.samples from monitoring wells MW-1, MW-4.and MW77;•located,cross to down=gradient on-site and down-gradient off-site;and cross-gradient off site, respectively, from the former UST excavation: ; ' • BTEX comP ounds were detected.in the water samples collected from MW-1'and MW24, the concentrations.of benzene_in both.samples exceeded the State of.California'maximum rcontaminant level (MCL) of 1 µg11 for drinking water, •, • -As.can'be seen'on'Table 2, the concentrations of analytes detected in-the ground water ' samples from the impacted on-site monitoring well(MW-1)have generally declined over the course of the sixrevious sampling/mor'itoritng events,but have rebounded during the four ,• P ' Advanced GeoEnvironmental,Inc.