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I ' 29 May 2001 ' AGE-NC Project No 99-0657 Page 3 of 4 ' Benzene was detected in all four water samples at concentrations ranging from 80,ug/l to MW3 to 3,900 ,ug/l in MW1 Toluene, ethylbenzene and xylenes were detected in all of the ground water samples collected, with the exception of ethylbenzene in MW3 at concentrations as high as 2,700 ' ug/l, 180 ,ug/l and 1,600 ,ug/l, respectively(MWI) MTBE was detected by EPA Method 8020 in ground water samples collected from wells MWi, IMW2 and MW4 at concentrations of 4,700 gg/l, 3,300 and 660 4g/1, respectively MTBE was confirmed by EPA Method 8260 in the same samples at concentrations of 4,200 gg/l, 3,400 µg11, ' and 750 ,ug/l, respectively and detected 1n the ground water sample collected from MW3 at a concentration of 46 ,ugll TBA was detected in the ground water sample collected from MW3 at a concentration of 17 ,ug/1 1,2-DCA was detected in ground water samples collected from MW 1, MW3 and MW4 at concentrations as high as 220 ,ug/l (MW 1) EDB and the other fuel oxygenated compounds were not detected in the ground water sample analysis The analytical results of water samples collected in April 2001 are summarized on Table 2 The laboratory report (MAI Lab I D No 64722 through 64725), QA/QC report and chain-of-custody form are included in Appendix B r• 4 0. SUMMARY AND CONCLUSIONS IThe following conclusions were drawn from the results of this investigation • The ground water elevations ranged from 9 10 to 9 36 feet above MSL Ground water is inferred to be flowing toward the southwest at an average gradient of 0 004 feet/feet The relative ground water elevation at the site decreased an average 1 06 feet between the January 2001 and April 2001 monitoring events • Concentrations of dissolved TPH-g, TPH-d, BTEX compounds and fuel oxygenates have decreased in wells MW1, MW2 and MW4 and increased in well MW3 since the last monitoring event in January 2001 The highest concentration of dissolved hydrocarbons is in monitoring wells MW1 and MW4 which are south and south-southwest and downgradient of the UST area Isocontour maps depicting the approximate distribution of dissolved TPH-g, MTBE and benzene are presented in Figures 4, 5 and 6 • The lateral extent of petroleum hydrocarbon-impacted ground water has not been defined 4dvanced CeoEnvnronmental,Inc I