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' 1$ . October 1997 ' AGE-NC Project No 95-0112 Page 3 of 4 • Low concentrations of petroleum hydrocarbons were detected in the ground water sample collected from MW-1 during the July 1997 monitoring event BTE&X concentrations ' remained well below the maximum contaminant levels (MCLs) for drinking water, an MCL has not been established for TPH-g Petroleum hydrocarbons were not detected in the remaining wells sampled • Oxygenating compounds were not detected in the samples collected at the site during the July 1997 monitoring event • Except for DCA, the concentrations of volatile organic compounds detected in MW-1 did not exceed the MCLs or action levels (ALs) for those compounds having established MCLs or ALs The DCA detected in MW-1 may be related to a regional plume of DCA that has ' impacted large portions of the City of Lodi • The concentrations of dissolved petroleum hydrocarbons have declined dramatically in MW-1 and MW-3, dropping from a high of 100,000 ppb to 190 ppb TPH-g and from 21,000 ppb to 0 35 ppb benzene in MW-1 TPH-g in MW-3 has declined from 20,000 ppb to <50 ppb, and benzene has declined from 2,900 ppb to <0 3 ppb Low concentrations of TPH-g and '• benzene in MWA and MW-5 have declined to non-detectable concentrations • Generally, the target analytes have not been detected in the perimeter monitoring wells, MW- 6, MW-7 and MW-8 ' * MTBE has been detected only once at the site (MW-7) at 4 1 ppb This detection has not been confirmed, but is well below the Central Valley Regional Water Quality Control Board ' recommended 35 ppb closure limit • The plume of hydrocarbon-impacted water on this site is not mobile and has had a steady ' decline of hydrocarbon concentrations • AGE believes that this plume does not pose a significant threat to ground water in the area 5.0 RECOMMENDATIONS ' Based upon data collected at the site, AGE recommends the following ' • A composite sample should be—collected from the stockpiled soil still on-site for _ characterization, and the soil should be disposed of appropriately ' • The site should be considered for closure It is unlikely that additional remediation at the site would be cost-effective or result in a significant reduction of the remaining hydrocarbon mass • Upon closure certification, all monitoring, vapor and sparging wells associated with-the site ' should be abandoned/destroyed in accordance with local regulations ' Advanced GeoEm ironmental,Inc.