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from MW-1.However,petroleum hydrocarbons were detected in groundwater from all three �- wells. The analytical results implied that gasoline migration through the soil was primarily downward until the groundwater interface was reached, followed by lateral migration in the ' capillary fringe. Initially, the groundwater gradient was east-northeast, probably in response to drawdown in Lodi Municipal Well #1, which was located approximately 350 feet east of the site; this may explain the high concentration of hydrocarbons in the water sample from MW-3. However, the regional hydraulic gradient is to the southwest, which probably accounts for the petroleum hydrocarbons detected in MW-2. The City of Lodi well has since been abandoned. ' 2.3 Initial Monitoring ' It is our understanding that no further work was performed at the site until November 1991. In November of 1991, Earth Systems Environmental (FSE) attempted to measure the depth to groundwater and collect water samples in wells MW-1 through MW-3. ESE reported that ' water levels had dropped below the screened intervals in MW-2 and MW-3 and the wells were dry. However, both water and floating product were present in MW-1, but no sample was collected. The product thickness was not reported by ESE. The depth to water in MW-1 was 60.12 feet. No further monitoring occurred in 1991. 2.4 Installation of Monitoring Wells MW-4 and MW-5 In January 1992, PHS/EHD required replacement of MW-2 and MW-3. Monitoring wells ' MW-4 and MW-5 were installed in June 1992. GeoAudit supervised the drilling and collected the samples. No petroleum hydrocarbons were detected in any of the soil samples from MW-4 or MW-5. Low to moderate concentrations of hydrocarbons were detected in water samples from both MW-4 and MW-5. Due to low water levels, none of the other wells could be sampled in ' June 1992. Measurement of the depth to groundwater in MW-1, MW-4, and MW-5 indicated that the groundwater gradient had rotated to the southwest, in accord with the regional gradient. (The City of Lodi Municipal Well #1 was abandoned prior to 1992.) Based on these results, GeoAudit recommended that two additional wells be installed to define the limits of the petroleum hydrocarbon plume in groundwater, one to the northwest ' of the building and one southwest of MW-5. Subsequently, PHS/EHD required three additional wells, all located east or north of MW-1. ' 2.5 Installation of Monitoring Wells MW-6, MW-7 and MW-8 Monitoring wells MW-6, MW-7, and MW-8 were installed in April 1993. Two soil samples ' from each well, one from the existing groundwater interface (55 feet) and one from the 000bo O An&SmI.e. 4 An t Mir Q1t4*W 1A7