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3.0 RESULTS 3.1 Depth to Groundwater and Groundwater Flow Direction The depth to groundwater on March 26 was between 24 5 and 25 feet below grade (Table 1) These depths are approximately 6 inches less than those that were measured in January Using the three-point method to contour these values yields a groundwater elevation (piezometric surface) map with a uniform gradient of 0 0013 ft/ft sloping to the northeast (Figure 3) This is the first time since the wells were installed that the flow direction was to the northeast, although the regional groundwater elevation map prepared by the San Joaquin County Flood Control District in 1993 shows the water table sloping in this direction 3.2 Laboratory Results Hydrocarbon concentrations in JLM-4 were slightly above the detection limit in June 2002 and January 2003, but were below the limit in September 2002 and again in March 2003 (Table 2) This well is probably located close to the northeastern limit of impacted groundwater In JLM-3, the TPH-g, benzene, and ethylbenzene concentrations rose sharply after declining in the previous two quarters, while toluene, xylene, MTBE, and 1,2-DCA remained stable Like JLM-3, concentrations in JLM-5 rose sharply after declining for the two previous quarters The results are plotted in Figure 4 The TPH-d concentration in JLM-3 was nearly identical to the TPH-g concentration, prompting the question of whether the reported diesel might actually represent degraded gasoline However, the laboratory reported that the TPH-g chromatogram was representative of relatively unmodified gasoline, while diesel-range compounds were significant in the TPH-d chromatogram This suggests that both gasoline and diesel are present at similar concentrations Diesel was also detected in JLM-5, at a concentration about 4 times greater than in JLM-3 4.0 DISCUSSION AND CONCLUSIONS For three consecutive quarters, water-elevation data indicated that groundwater flow is to the southeast This quarter, the data suggest that flaw was northeast toward JLM-4 Despite this, no hydrocarbons were detected in JLM-4, while concentrations in JLM-3 increased after declining for the past 6 months In the Fourth Quarter 2002 Report, we suggested that the declining concentrations might be due to dispersion The sharp increase this quarter and the absence of hydrocarbons in JLM-4 might also suggest that there is a time lag between changes in the direction of groundwater flow and changes in hydrocarbon concentrations If so, concentrations in JLM-4 might increase during the second quarter of 2003 However, concentrations also increased sharply in JLM-5, which continues to be . upgradient of the source This increase could not be attributed to a change in groundwater flow direction or to an associated time lag At the same trine, there was very little change 3