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EPLIt. Ms, Evelyn Hubel February 25, 1999 Page 2 Analytical results of' groundwater samples collected from 3 existing onsite groundwater monitoring wells indicate the following: ' . Benzene was detected at 1.1 ppm in the groundwater sample collected from monitoring well MW-4. This concentration exceeds the California Maximum Contaminant Level (MCL) of 1.0 ppm for benzene in drinking water; however, the 1.1 ppm value is within historical values of benzene measured in monitoring well MW-4. • Ethylbenzene and total xylenes were detected at 2.2 ppm and 16 ppm, respectively, in the groundwater sample collected from monitoring well MW-4. These concentrations are below the California MCL and are within historical values for monitoring well MW-4. 1 Total lead was detected at 0.0097 ppm in the groundwater sample collected from monitoring well MW-1. This concentration is below the U.S. EPA MCL of 0.015 ppm for lead in drinking water. Total chromium was also detected at concentrations up to 0.025 ppm in groundwater samples collected from 2 of the monitoring wells. These concentrations are below the California MCL of 0.05 ppm for total chromium in drinking water. Provided below are a summary of pertinent findings from ENSR's Phase ! assessment, and a description of the investigative methods and analytical results of the limited Phase II investigation conducted at the subject site. Summary of Phase I Findings j The site inspection conducted during ENSR's Phase I assessment revealed the presence of 4 floor drains with associated sumps in the former auto body shop building; 5 floor drains with associated sumps and 5 sub-grade hydraulic auto body lifts in the service bay building. Oil stains were observed on the floors in the vicinity of the sumps. Because the floors were reportedly washed on a regular basis, petroleum leaks or spills may have been washed.into the floor drains and sumps potentially contaminating subsurface soil. Moreover, the 5 sub-grade auto body lifts may have contained PCB coolant oils. One waste oil UST and two 500-gallon gasoline USTs were removed from the site in 1993. Although petroleum hydrocarbon constituents were not detected above regulatory action levels in soil samples collected from the tank excavations, elevated levels of TPH as gasoline, BTEX, and methyl-tertiarty-butyl-ether (MTBE) were detected in groundwater samples collected from 5 onsite groundwater monitoring wells in December 1998. Collected soil and groundwater samples were not analyzed for total lead or other heavy metals that may have been constituents of materials contained in the USTs. The local oversight regulatory agency, the San a .. ,Joaquin County Public Health Services Environmental Health Division, indicated that following