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1 <br />' 29 January 2004 <br /> AGE-NC Project No 96-0263 <br /> Page 3 of 4 <br /> 3 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br />' TPH-g was detected in water samples MW-2, MW-4, MW-5 and MW-7 at concentrations ranging <br /> from 260 micrograms per liter(µg/1) in MW-4 to 24,000 µg/1 in MW-7 <br /> IBenzene was detected in water samples MW-2 and MW-7 at concentrations of 6 4µg/1 and 320 µg/l, <br /> respectively Toluene was detected in sample MW-7 at a concentration of 27µg/1 Ethylbenzene was <br />' detected in samples MW-2 and MW-7 at concentrations of 8 1 µg/1 and 70µg/1, respectively Total <br /> xylenes were detected in samples MW-2, MW-4, MW-5, MW-7 and MW-8 at concentrations <br /> ranging from 3 0 µg/1 (MW-4) to 65 µg/l (MW-7) <br />' MTBE was detected in samples MW-2, MW-4 MW-5 and MW-7 at concentrations ranging from <br /> p � g g <br /> 230 µg/l(MW-4)to 33,000 µg/1 (MW-7) TAME was detected in sample MW-7 at a concentration <br />' of 35 µg/1 No other fuel additives were detected in the ground water samples collected from the site <br />' The current and past ground water sample analytical results are summarized on Tables 2 and 3 <br /> Copies of the laboratory report(CTEL Laboratory IDs 0312-119-1 through 0312-119-11), QAIQC <br /> report and chain-of-custody form are in Appendix B <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> Based on the results of this investigation, AGE concludes that <br /> I • Depth to ground water ranged from 7 07 feet to 8 25 feet below the tops of the well casings <br /> Ground water elevations at the site ranged from 28 65 feet above mean sea level (MSL) in <br /> well MW9 to 29 48 feet above MSL in well MW1I The ground water at the site was <br /> inferred to be flowing to the northwest at an average gradient of 0 005 feet/feet <br /> • Target analytes, including TPH-g, BTEX compounds, MTBE and/or TAME were detected <br /> in ground water samples collected from wells MW-2, MW-4, MW-5, MW-7 and MW-8 <br /> Detected concentrations of target analytes were generally consistent with previous results <br /> from ground water analyses The current concentrations of benzene to TPH-g, when <br /> compared, for a ratio of approximately 1 3 %, which indicates a natural attenuation of the <br /> dissolved benzene at the site However,the MTBE concentrations have remained stable over <br /> the monitoring period,therefore,no evidence of natural attenuation for the dissolved MTBE <br /> can be documented <br /> • The dissolved hydrocarbon plume extends northward from the former UST and dispenser <br /> areas, but not beyond the down-gradient monitoring wells (MW8, MW9 and MW10) The <br /> dissolved phase plume has been defined laterally in all directions Isoconcentration maps <br /> illustrating the approximate extent of TPH-g, benzene and MTBE-impacted ground water <br /> I are depicted on Figures 4, 5 and 6 <br /> Advanced GeoEnvironmental,Inc <br /> I <br />