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Page 2 August 30, 1994 BAE31604.AS.T8 As reported in the RI/FS, benzene was found to exceed the hazardous waste Toxicity Characteristic Leaching Procedure (TCLP) level for benzene of 500 µg11 in Monitoring Wells MW-DIS-1 and -2. Benzene concentrations in Monitoring Wells MW-DIS-1, -2, -3, and -7D have exceeded the California Maximum Contaminant Level (MCL) for benzene of 1 J.g/l Del Monte submitted a conceptual remediation plan to Michael Collins of San Joaquin County Public Health Services (PHS) on August 19, 1993. The remediation plan specifies air sparging combined with soil vapor extraction (AS/SVE) to remediate the source of gasoline constituents in the subsurface beneath the Disco Property. The purpose of the AS/SVE system is to significantly reduce further dilution of petroleum hydrocarbon into the groundwater. GROUNDWATER MONITORINGIQUALITY The quarterly monitoring event conducted on July 20, 1994 consisted of water level t measurements and groundwater sampling. Water level depths were measured in monitoring wells MW-DIS-1 through MW-DIS-7S and MW-DIS-7D. Monitoring well locations and groundwater elevation contours are shown on Figure 1. The groundwater elevation contour lines shown on Figure 1 indicate that the direction of groundwater flow generally trends northwesterly. In the vicinity of the former gasoline tanks it trends more westerly. The small groundwater elevation differences between all the monitoring wells indicates a shallow gradient. The ground water elevations decreased by approximately 1.0 to 1.5 feet in all wells since the previous quarter. Historical groundwater elevation data is summarized on Table 1. Monitoring wells MW-DIS-1, -2, -3, -4, -6, -7S, and -7D were sampled as part of the quarterly/annual groundwater quality monitoring program. Monitoring well purge and sampling data are attached. The groundwater samples were analyzed by Quality Analytical Laboratory, Redding CA, for total petroleum hydrocarbons (TPH) as gasoline; and benzene, toluene, ethylbenzene, and xylenes (BTEX) (EPA method 801518020). Results of the July 20, 1994 sampling event and results from previous sampling events are summarized in Table 2. The analytical results indicate that petroleum hydrocarbon concentrations in the wells adjacent to the former UST (MW-DIS-1 and -2) are still high. Down gradient wells MW- DIS-5, -6, and -7S were all below the detection limit. The sample from the deeper ( monitoring well MW-DIS-71) showed detectable concentrations of benzene and ethylbenzene.