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solution between wells. The water samples were collected with a disposable plastic Mailer and <br /> Mplaced in 40-m1 vials. The vials were labeled and logged and placed in a cooled ice chest. <br /> 4.0 RESULTS <br /> 4.1 Depth to Groundwater <br /> Table 1 shows the depth to groundwater and the calculated groundwater elevation. The depth has <br /> risen several inches in both KF-1 and KF-2, but has dropped slightly in KF-3. <br /> The significant rise in the piezometric surface since 1994 has continued. The depth to groundwater <br /> at that time was 19 feet, within a foot of the aquitard-aquifer contact. The monitoring yells were <br /> therefore screened from 15 to 30 feet. With the rise in the piezometric surface, the static water level <br /> in the wells is still 7 to 8 feet above the screened interval. <br /> 4.2 Groundwater Gradient <br /> The data in Table 1 were used to contour the piezometric surface and interpret the grc undwater <br /> flow direction, which are illustrated in Figure 3. Assuming that the depth measurement fi om KF-3 <br /> is correct, the piezometric surface has again reversed direction and now slopes to the southwest, as <br /> it did during the first half of 1998, immediately after the tank removal. <br /> 4.3 ILn:;omCoo7 Res^-r3uz <br /> As in the past, a gasoline odor was noticeable in all wells when they were purged, although the odor <br /> was not as strong as it was in 1997. Gasoline and BTEX compounds were detected in all three <br /> wells, at slightly higher concentrations than in late 1998 but still at lower concentrations than in <br /> previous monitoring events (Table 2). The samples were not analyzed for gasoline oxy€,nates, in <br /> order to keep the analytical costs down until Mr. Peters has qualified for reimbursement; from the <br /> UST Fund. <br /> Figure 4 is a contour map of TPH-gasoline and benzene concentrations in the three groundwater <br /> samples collected during the first quarter of 1999. The true lateral extent of contamination is <br /> probably greater than shown, because the samples were not collected at the soil-groundwater <br /> interface but at a depth 7 feet above this interface in the wells. <br /> 5.0 CONCLUSIONS AND RECOMMENDA71ONS <br /> 0 Due to the continuing situation of a high water table in the Stockton area, we recommend that <br /> additional wells be installed and screened at a shallower depth (5-25 feet) so that mor, accurate <br /> laboratory data can be obtained from groundwater samples. At least four additional wells will <br /> 3 <br />