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California was retained in November, 1990 to perform further subsurface investigation. Two borings were drilled, one was completed as a groundwater monitoring well, and soil and water samples were collected for analysis . Hydrocarbons were detected to the bottom of the soil boring ( 70 feet) and to a depth of 85 feet in the monitoring well, and both gasoline and diesel were detected in the groundwater sample from the well . The results obtained from the borings necessitated further investigation, and Upgradient was retained in August, 1994 to superva-se the installation of two additional monitoring wells (GT-1 and GT-2 , Figure 2 ) . Five soil samples from GT-1 were selected for laboratory analysis, and all five contained both diesel and gasoline-range hydrocarbons . Total Petroleum Hydrocarbon (TPH) concentrations decreased downward from 7050 mg/kg at 35 feet to 104 mg/kg at 55 feet. Three samples were selected from GT-2 for analysis . A TPH concentration of 288 mg/kg was reported at a depth of 55 feet; no contamination was detected at 50 feet or 60 feet. Diesel was detected in the groundwater sample from both wells, and gasoline was also detected in the sample from GT-2 . Groundwater was also sampled in MW-1, but no hydrocarbons were detected. Groundwater elevations measured in September did not provide conclusive evidence regarding the direction of groundwater flow, but suggested flow to the northwest. Data previously published by the San Joaquin County Public Works Department had indicated that . the prevail2-ng flow direction was to the south or southwest. Therefore, Upgradient measured the depth to groundwater in both November and December to obtain additional information on flow direction. As reported in the 4th Quarter Report, groundwater elevations in all wells were nearly equal, but suggested groundwater flow to the south. The data obtained in January 1995 also suggested a southward groundwater flow direction. An increase in gasoline concentrations in groundwater was correlated with a rise in the groundwater table, suggesting that groundwater is dissolving hydrocarbons from the soil above a depth of 75 feet. 3 .0 MONITORING PROCEDURES Groundwater monitoring took place on July 7 , 1995 . Upon arrival at the site, Upgradient personnel were unable to locate either GT-1 or GT-2 . Both wells had been buried as a result of recent grading activities at the site . After approximately one hour, the wells were located and uncovered with the help of Mr. Ken Gillies . After the wells were opened, a Solinst water level meter was used to measure the depth to groundwater prior to bailing and sampling. Slightly more than three well volumes of water ( 14 to 20 gallons) were purged from each well and stored in a 55-gallon drum near MW- 1 . A Corning meter was used to measure temperature, conductivity, 10 and pH during purging to confirm that these parameters stabilized 2