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24 July 2001 <br /> AGE-NC Project No 96-0263 <br /> Page 3 of 4 <br /> 3 2 LABORATORY RESULTS OF GROUND WATER SAMPLES <br />' TPH-g was detected in the water samples collected from monitoring wells MW2, MW4, MW5 and <br /> MW7 at concentrations ranging from 420 micrograms per liter(µg/1) in MW4 to 2,800,ug/l in MW7 <br /> Benzene was detected in the water samples collected from monitoring wells MW2,MW4, MW5 and <br /> MW7 Benzene concentrations ranged from 38 µg/l in MW4 to 390 ug/l in MW7 Toluene, <br /> ethylbenzene and total xylenes were detected in the same samples at concentrations ranging from <br /> 1 4µg/1 of toluene in MW4 to 330 µg/1 of toluene in MW7 <br /> MTBE was detected by EPA method 8020 in monitoring well samples MW2, MW4, MW5, MW7 <br /> I and MW8 at concentrations ranging from 13 µg/l in the sample from MW8 to 16,000µg/1 in MW7 <br /> MTBE was confirmed by EPA method 8260m in the same samples at concentrations ranging from <br /> 11 µg/1 in MW8 to 13,000 4g/l in MW7 No other fuel oxygenates were detected in the ground water <br /> samples collected from the site <br /> The current and past ground water sample analytical results are summarized on Table 2 The <br /> laboratory report(MAI Sample ID Nos 71693 through 71703), QA/QC report and chain-of-custody <br /> form are included in Appendix B <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> The following conclusions were drawn from the results of this investigation <br /> I Depth to ground water ranged from 6 84 feet to 8 00 feet below the well casing tops The <br /> prevailing ground water flow direction in June 2001 was inferred to be towards the <br /> north-northwest at an average hydraulic gradient of 0 005 feet/feet <br /> • 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 MW 10) 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 /> I <br /> 5.0. RECOMMENDATIONS <br /> I Based on the findings of the this investigation, AGE recommends <br /> • <br /> • Continued quarterly monitoring of the groundwater monitoring wells The next monitoring <br /> i event should be performed in September 2001 <br />