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Table 5 summarizes the historical groundwater elevation data at the site Between 1992 and 1996, the depth to groundwater was measured between 51 50 feet and 79.85 feet The groundwater elevation at the site ranged 24 65 feet between 1992 and 1996, with an overall rising trend in the groundwater, associated with an increase in precipitation in the region Groundwater at the site was measured at an approximate depth of 60 feet bgs in August 1996 (Table 5) 6.0 Beneficial Uses of Water The Water Quality Control Plan (Basin Plan) for the San Joaquin River Basun lists the beneficial uses of groundwater within San Joaquin County as municipal and domestic water supply, irrigation, stock watering and service supply Groundwater is known to be used for domestic, industrial, and agricultural purposes throughout the area surrounding the site A production well (State Well Number 02N06E36NO2M) monitored by the Department of Water Resources is located approximately 1,500 to 2,000 feet to the northeast of the site Two production wells are located within the Lipton facility, approximately 550 feet to the southwest and approximately 250 feet to the north of the site 7.0 Extent of Petroleum Hydrocarbons in Site Soils TPH as diesel was identified as the only contaminant of concern in the soil. Initial site investigations indicated that the lateral extent of the soil impacted with TPH as diesel was approximately 80 feet from the former tank locations, at a depth of 70 to 75 feet bgs, at a concentration of 1.0 to 13 mg/Kg (Figures 4 and 10). In 1993, borings B-101 to B-104, surrounding the tank excavation, yielded low level detections of TPH as diesel (maximum of 6 8 mg/Kg) (Figures 4 and 5) The results of more recent site investigations (TT, 1995b) suggest that the lateral extent of the soil impacted by TPH as diesel have decreased to approximately 40 feet around the site (Figure 10) In 1995, verification boring SB-1 yielded reduced levels of TPH as diesel as compared to MW-4 (Figures 4 and 6) In verification boring SB-2 the measured TPH as diesel concentrations did not exceed detectable levels (<0.5 mg/Kg) In comparison, boring B-102, sampled in 1993 and located further from the tank excavation, yielded detectable levels of TPH as diesel (1.3 to 3 1 mg/Kg) in the sand unix at approximately 50 feet bgs (Figures 4 and 6) Vertical extent of the soil impacted by TPH as diesel was encountered in initial investigations in 1992 at a maximum depth of approximately 70 feet bgs Boring B-1 had a TPH as diesel concentration of 13 mg/Kg at 70 feet bgs. TPH as diesel was also detected in 1993 at 2,000 MZ/06-13-97/VDBF/97-OOM BK 4