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r rst ' 25 February 2004 • AGE-NC Project No 99-0657 ' Page 3 of 4 ' One or more BTEX compounds were detected in water samples collected from wells MW-1 through MW-5 with maximum concentrations of 250µg/1 benzene,670 µg/1 toluene,240µg/1 ethylbenzene and 918 µg/1 xylenes all from sample MW-1 ' MTBE was detected in water samples collected from wells MW-1 through MW-4 and MW-6 at concentrations ranging from 60 µg/1 (MW-4) to 540 µg/1 (MW-2) ' 1,2-DCA was detected in water samples collected from MW-4 and MW-6 at a maximum concentration of 20 µg/l (MW-4) ' No other analytes were detected at or above laboratory detection limits In the ground water samples analyzed The analytical results of water samples collected in October 2003 are summarized on ' Table 2 The laboratory report(CTEL Lab Project No CT214-0310046), QA/QC report and chain- of-custody form are included in Appendix C ' 4.0. SUMMARY AND CONCLUSIONS lie The following conclusions were drawn from the results of this investigation • The ground water elevation averaged approximately 4 59 feet above MSL Ground water is inferred to be flowing toward the southwest with an average ground water gradient of 0 004 foot/foot The ground water elevation at the site is the lowest level recorded to date, with a average decrease of 0 10 feet between the July 2003 and October 2003 monitoring events • The highest concentrations of dissolved hydrocarbons occurred in monitoring wells MW-1, MW-4 and MW-6, which are located down-gradient of the UST area Concentration maps depicting the approximate distribution of dissolved TPH-g,benzene and MTBE are presented in Figures 4, 5 and 6 • Concentrations of dissolved TPH-g, BTEX and fuel additives have decreased significantly in MW-4, MW-5, MW-6, MW-7, and MW-8 Concentrations of dissolved TPH-g, BTEX ' and fuel additives increased two-fold 1n MW-1,MW-2 and MW-3 This is the opposite trend that was seen In July 2003, the coincidence of these two trends may likely indicate an active migration ofthe dissolved phase hydrocarbon plume or the localized desorption of additional hydrocarbons at the former UST area • The lateral extent of ground water has been defined to the north, east and southeast of the I UST area The vertical extent ofpetroleum hydrocarbon-impacted groundwater has not been defined • The lateral extent of Impacted soil in the vadose zone has been defined IAdvanced GeoEnvironmental,Inc I