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I29 November 2001 <br /> • AGE-NC Project No 96-0263 <br /> IPage 3 of 4 <br /> I3 2 LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> TPH-g was detected in the water samples collected from monitonng wells MW2,MW4,MW5 and <br /> MW7 at concentrations ranging from 98 micrograms per liter(µg/1)in MW4 to 5,900µg/1 in MW7 <br /> Benzene was detected in the same water samples at concentrations ranging from 11 µg/1 in MW4 <br /> to 820µg/1 in MW7 Toluene,ethylbenzene and total xylenes were also detected in the same samples <br /> at concentrations ranging from 0 74 µg/1 of toluene in MW4 to 890 µg/l of toluene in MW7 <br /> MTBE was detected by EPA method 8020 in monitoring well samples MW2, MW4, MW5,MW7 <br /> and MW8 at concentrations ranging from 6 9 µg/1 in the sample from MW8 to 18,000 µg/1 in MW7 <br /> MTBE was confirmed by EPA method 8260m in the same samples at concentrations ranging from <br /> 6 8 µg/1 in MW8 to 20,000 µg/1 in MW2 and MW7 No other fuel oxygenates were detected in the <br /> ground water samples collected from the site <br /> I The current and past ground water sample analytical results are summarized on Table 2 Copies of <br /> the laboratory report (MAI Sample ID Nos 79963 through 79973), QA/QC report and chain-of- <br /> custody form are in Appendix B <br /> lie <br /> 4 0 SUMMARY AND CONCLUSIONS <br /> Based on the results of this investigation, AGE concludes that <br /> I0 Depth to ground water ranged from 6 90 feet to 8 02 feet below the well casing tops The <br /> prevailing ground water flow direction in September 2001 was inferred to be towards the <br /> north-northwest at an average hydraulic gradient of 0 005 feet/feet <br /> t0 The dissolved hydrocarbon plume extends northward from the former UST and dispenser <br /> areas, but not beyond the two down-gradient monitoring wells (MW9 and MW10) The <br /> dissolved phase plume has been defined in all directions Isocontour maps illustrating the <br /> approximate extent of TPH-g-,benzene-and MTBE-impacted ground water are depicted on <br /> Figures 4, 5 and 6 <br /> 5.0. RECOMMENDATIONS <br /> Based on the findings of the this investigation, AGE recommends <br /> • Continued quarterly monitoring of the ground water monitoring wells The next monitoring <br /> • event should be performed in December 2001 <br /> • A feasibility testing work plan should be prepared to assess remediation alternatives at the <br /> site <br /> I <br />