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29 March 2002 <br /> i AGE-NC Project No 96-0254 <br /> Page 4 of 5 <br /> MTBE was detected by EPA Method 8260 in the samples collected from MW-1B, MW2B and <br /> MW-4 at concentrations of 21 ug/l, 1 6 µg/1 and 2 4µg/l,respectively No other fuel additives were <br /> detected in the ground water samples <br /> The analytical results are summarized in Table 2 Copies of the laboratory reports(MAI Laboratory <br /> ID 88957 to 88966), QA/QC reports and chain-of-custody forms are in Appendix C <br /> 4.0 SUMMARY AND CONCLUSIONS <br />' Based on the data collected during this monitoring period, AGE concludes <br />' The depth to ground water at the site was between 6 70 to 8 47 feet below the well casing <br /> tops Ground water elevations at the site increased an average 0 24 feet between the October <br /> 2001 and January 2002 sampling events The prevailing ground water flow direction at the <br />' site was generally toward the north, consistent with the previously determined flow <br /> directions <br /> I • Petroleum hydrocarbon-impacted ground water was encountered in samples from monitoring <br /> wells MW-1B and MW-4 with benzene concentrations exceeding the State of California <br /> maximum contaminant level (MCL) of 1 µg/1 in samples collected from the wells Low <br /> concentration of MTBE were detected in the ground water samples collected from MW-IB, <br /> MW2B and MW-4 The MTBE concentrations exceeded the State of California primary <br /> maximum contaminant level (MCL) of 13 ppb in the sample collected from MW1B In <br /> general,overall hydrocarbon concentrations have increased slightly this quarter Isocontour <br /> maps illustrating the approximate distribution of dissolved TPH-g, benzene and MTBE in <br /> the shallow screened wells are presented in Figures 4, 5, and 6 <br /> • The laboratory results of the microbiological analysis indicate moderate populations of <br /> organisms capable of gasoline metabolism However,nutrient concentrations are at moderate <br /> to high levels for ongoing bioremediation <br /> I5.0. RECOMMENDATIONS <br /> I Based on the results of this investigation, AGE recommends, continued quarterly ground water <br /> monitoring at the site The next monitoring event should be scheduled for April 2002 Additionally, <br /> AGE recommends the preparation of a Problem Assessment Report (PAR). <br /> • <br /> Advanced GeoEnvironmental Enc <br />