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• were re-sampled on October 6 The Gillies domestic*ell was also sampled on October 6 Sample G-1 A was collected from the sample port on the top of the well pump, and sample G-1 B was collected from the valve on the storage tank All eight of the samples were analyzed for TPH-diesel and TPH-gasoline by EPA method 602 and for BTEX and MTBE by method 8020 3.0 RESULTS 3.1 Groundwater Gradient and Flow Direction Depth-to-groundwater measurements and calculated groundwater elevations are presented in Table 1 Results from previous momtoring events are included for comparison The static water level is approximately 8 feet deeper than it was in June of this year, and now averages approximately 55 feet in depth Hence, it has now dropped below the base of the Modesto Aquifer and is present within the low-permeability silt bed that constitutes the Modesto Aquitard In some of the bonngs, this is the interval in which the highest concentrations of contaminants were detected (e g GT-3, GT-7, GT-10, GT-11) The present elevation (relative to sea level) is almost minus 28 feet The calculated water table elevations were used to construct the groundwater gradient map in Figure 3 The gradient is now much less steep than it was in June, when it appeared to slope rather • strongly to the northwest or north At this time, the gradient is flat, with no apparent flow direction Less than 0 5 inches separates the highest elevation from the lowest elevation of the static water level 3.2 Laboratory Results Significant changes in contaminant concentrations also occurred during the third quarter (Table 2) Diesel concentrations again decreased markedly in GT-10, but increased significantly in GT-1 and GT-2 In addition, diesel was detected in GT-6 for the first time since December of 1997 Diesel was not detected in the samples that were collected from the domestic well tank in July or October, but it was detected in the sample that was collected from the well in October, apparently confirming the June result from the water faucet outside the men's bathroom Gasoline was detected in four of the eight samples collected in October Gasoline was detected right at the reporting limit in GT-6, it had not been previously detected in this well Concentrations in the other wells were generally within the ranges of concentrations that had previously been detected in these wells Benzene and the other aromatic compounds were again detected in GT-10, at concentrations that are still low but are higher than any previously detected in this well Some of these analytes were also detected in GT-1, GT-2, GT-3, and GT-6, even though the static water level is still more than 25 feet above the screened interval in most of these wells Even more surprising, MTBE was • detected at a concentration of 100 ppb in GT-6 This sample was not re-run using EPA method z