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11 October 2002 <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 the water samples collected from monitoring wells MW2,MW4,MW5, and <br /> MW7 at concentrations ranging from 150 micrograms per liter (µg/1) in MW4 to 22,000 µg/1 in <br /> MW7 <br /> Benzene was detected in the water samples collected from monitoring wells MW2,MW5 and MW7 <br /> at concentrations ranging from 8 7 µg/1 in MW2 to 830 µg/1 in MW7 With the exception of toluene <br /> in sample MW5, toluene, ethylbenzene and total xylenes were also detected in the same samples, <br /> at concentrations ranging from 2 3 µg/1 of toluene in MW2 to 1,100 µg/1 of toluene in MW7 In <br /> addition,toluene was detected in the sample collected from well MW4 at a concentration of 1 2 µg/1 <br /> MTBE was detected in monitoring well samples MW2, MW4, MW5, MW6 and MW7 at <br /> concentrations ranging from 2 3 µg/1 in the sample from MW6 to 22,000 µg/1 in MW7 TAME and <br /> TBA were detected in the sample collected from MW7 at concentrations of 36 µg/1 and 470 µg/1, <br /> respectively No other fuel additives were detected in the ground water samples collected from the <br /> site <br /> lie The current and past ground water sample analytical results are summarized on Table 2 Copies of <br /> the laboratory report (CTEL Lab I D No 0210-006-1 through 0210-006-11), QA/QC report and <br /> 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 /> a Depth to ground water ranged from 6 97 feet to 8 10 feet below the well casing tops The <br /> prevailing ground water flow direction in September 2002 was inferred to be towards the <br /> north-northwest at an average hydraulic gradient of 0 006 feet/feet <br /> 0 Benzene was not detected this quarter in deep-screened well MW-6 (well-screened interval <br /> between 27 and 32 feet bsg) MTBE was detected for the second straight quarter in well <br /> MW6 at a concentration of 2 3 µg/l, which ;s below the State of California Primary <br /> Maximum Contaminant Level (MCL) of 5 0 gg/1 for MTBE in drinking water <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 Isoconcentrataon maps <br />' illustrating the approximate extent ofTPH-g-,benzene- and MTBE-impacted ground water <br /> . are depicted on Figures 4, 5 and 6 <br /> 1 <br />