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KLEINFELDER 1i Ground water monitoring well MWA has been sampled during three separate events. The analytical results are as follows: Monitoring Well Sampling Events/Results gg/l TPH- TPH- Ethyl- Date Laboratory Gasoline Diesel Benzene Toluene benzene Xvlenes Event 1 Columbia 100 ND 1:6 ND ND ND June 1991 Event 2 Alpha 60 ND ND ND ND ND September 1991 Columbia 220 NA 0.8 ND ND ND FGL ND NA ND ND ND - ND Event 3 Alpha ND NA ND ND NID ND January 1992 ND - Not Detected IATA - Not Analyzed Low concentrations of TPH-Gasoline and benzene were detected in the izutiaI sampling round. Benzene was detected at 1.6 Ag/l, which is just above the State Maximum Contaminant Level (MCL) of 1.0 Ag/1 for drinking water. In the second sampling round, low concentrations of TPH-Gasoline were detected by two of the three laboratories, and benzene was detected by one of the three laboratories. The single benzene concentration detected in the second sampling round was 0.8 gg/1 which is below the State MCL of 1 Ag/l. It should be noted that the sample submitted by San Joaquin County Public Health Services from the second round of sampling did not contain detectable concentrations. TPH-Gasoline and BTEX constituents were not detected in the third round of sampling conducted by Meinfelder. The water levels in the first and third sampling events are approximately the same, indicating that the same water bearing zones are being sampled during each of the events. Based on the lack of ground water table elevation fluctuanor., the low concentrations detected during the first two sampling events, and the lack of detectable concentrations during the third sampling event, ground water in MWA does not appear to have been . significantly impacted by vertical migration of petroleum hydrocarbons. Additionally, FR1-92-15 Page 16 of 21 Copyright 1992 Kleinfelder, Inc.