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05 November 2001 - <br /> AGE-NC Project No. 95-0106 <br /> I -Page 3 of 5 <br /> 4.2. ANALYTICAL RESULTS OF GROUNDWATER SAMPLES <br /> Petroleum hydrocarbons,were detected in the ground water samples collected from monitoring wells <br /> MW-1 and MW-4; MWA is located slightly cross and down-gradient from, the former UST <br /> I excavation and MW-4 is locatedfurther north in the generally down- adient direction. TPH-g.was <br /> detected'dt concentrations of 720 micrograms per liter(gg/1) and 8,300 µg/1;respectively,in samples <br /> from the two-wells. Benzene was detected at 200 µg/1 and 230 gg/l in samples from MW-1' and" <br /> MW-4,respectively. Other volatile aromatic compounds were detected at concentrations of 7.0 gg/1', <br /> and 20 gg/l toluene, and 14 µg/l and 160 gg/1 ethylbenzene and 3.2 gg/l and 230 gg/l xylenes in <br /> I; samples from MW-L and MW-4, respectively. <br /> Neither TPH-g nor BTEX compounds were detected in the groundwater samples from monitoring <br /> wells MW-2, MW-3, MW-5; MW-6 (upper), MW-6 (lower) and MW-7. MTBE was not detected <br /> in any of the ground water samples. Analytical results of ground.water samples are summarized on <br /> Table 2. The laboratory report (MAI Lab ID 75288 through 75295), QA/QC and chain-of-custody <br />'. are included in Appendix B. <br /> 5.0. SUMMARY AND CONCLUSIONS t <br /> The following conclusions were drawn from'theresults of the site investigation: , <br /> •' The ground water was generally northward on 17 August 2001, and was calculated"to range <br /> from 0.001.toward.the north-northwest.to Q,003 toward. the north-northeast. . <br /> • Dissolved petroleumhydrocarbons were detected in groundwater samples'from monitoring <br /> wells MW-1 and MW-4, located cross to down-gradient on-site and down-gradient off-site, <br /> respectively, from'the_former UST excavation. <br /> BTEX compounds were deteefed'in the water samples collected from MW-Vand MW-4, ilie <br />' concentrations of benzene in both. samples exceeded the State. of California maximum <br /> contan-iinanit level (MCL) of 1 µg/1 for drinking water. <br /> • :. As can be seen on Table 2, the concentrations of analytes detected in the,ground water <br /> samples from the iiiipacted on-site monitoring well (MW=1) have remained'reiatively stable <br /> �duritig.the course 6f the seven previous sampling/monitoring events: The'cancentratioiis of <br /> analytes detected in the ground water.sarnples from MW-4 have increased significantly since <br /> I theprevious 'monitoring e.vent although they are within the ran e'detected since monitoring, <br /> began in 1996. <br /> IAnalytical data,from monitoring wells MW-2 and MW-7 limits the horizontal extent of <br /> ` 'dissolved hydrocarbons 'south and east of the site, respectively. Analytical data from wells <br /> Advanced CeuEnvironmental,Inc, <br />