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1 24 November 1997 <br /> AGE-NC Project No 95-0112 <br /> ' Page 3 of 4 <br /> ' 4.0. CONCLUSIONS/SUMMARY <br /> Based upon data collected from the site, AGE concludes the following <br /> ' I <br /> • Low concentrations of petroleum hydrocarbons were detected in the ground water sample <br /> collected from MW-4 during the October 1997 monitoring event BTE&X concentrations <br /> detected with EPA Method 8020 remained below the maximum contaminant levels (MCLS) <br /> ' for drinking water, however,benzene quantified by EPA Method 8260 was above the MCL <br /> of 1 0 ppb for the compound An MCL has not been established for TPH-g Petroleum <br /> hydrocarbons were not detected in the remaining wells sampled <br /> • Oxygenating compounds were not detected in the samples collected at the site during either <br /> the July or October 1997 monitoring event <br /> ' • Except for DCA in MW-4 and MW-5, the concentrations of volatile organic compounds <br /> detected at the site did not exceed the MCLs or action levels (ALs) for those compounds <br /> having established MCLS or ALs The DCA detected at the site may be related to a regional <br /> plume of DCA that has impacted ground water underlying large portions of the City of Lodi <br /> • The concentrations of dissolved petroleum hydrocarbons have declined dramatically at the <br />' site, dropping from a high of 100,000 ppb to <50 ppb TPH-g and from 21,000 ppb to <0 3 <br /> ppb benzene in MW-1 TPH-g in MW-3 has declined from 20,000 ppb to <50 ppb, and <br /> benzene has declined from 2,900 ppb to <0 3 ppb Only low concentrations of TPH-g and <br /> benzene have been detected in MW-4 and MW-5 <br /> • Generally,the target analytes have not been detected in the perimeter monitoring wells,MW- <br /> 6, MW-7 and MW-8 <br />' • MTBE has been detected only once at the site (MW-7) at 4 1 ppb This detection has not <br /> been confirmed, but is well below the Central Valley Regional Water Quality Control Board <br />' recommended 35 ppb closure limit <br /> • The plume of hydrocarbon-impacted water on this site is not mobile and has had a steady <br />€' decline of hydrocarbon concentrations <br />€ • AGE believes that this plume does not pose a significant threat to ground water in the area <br /> 50. RECOMMENDATIONS <br /> • Based upon data collected at the site, AGE recommends the following <br /> Advanced CcoEnvironmcntal,Inc <br />