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I 3.0 RESULTS 3.1 Depth to Groundwater Table 1 provides all depth-to-groundwater measurements and calculated groundwater elevations The depth ranged from 61 3 to 62 73 feet At this depth, it is 2 feet below the bottom of the shallowest well (GT-10), 7 feet below the top of the screened interval in GT-5 and GT-6, 13 feet above the top of the screened interval in GT-1 and GT-2, and-8-18 feet below the base of the shallowest sand bed in the Modesto Formation The base of this bed, referred to as the Modesto channel or Modesto aquifer in previous reports, ranges in depth from about 44 to 54 feet in the existing wells 3.2 Hydraulic Gradient and Groundwater Flow Direction The calculated water table elevations were used to construct the groundwater elevation map in Figure 3 The elevation contours trend east-west in a relatively linear pattern This is a more stable configuration than was observed in the second quarter of 2002, when the contours formed a sharp S-curve and depicted an unstable condition The water table slopes northward at 0 0045 ft/ft, indicating that groundwater flow is in that direction 3.3 Analytical Results Diesel was detected in three of the monitoring wells (Table 2) The concentrations are very low in both GT-1 and GT-5 and are no more than 10 parts per billion (ppb) above the method detection limit This is consistent with previous conclusions that the lower limit of soil contamination is only a few feet below the base of the Modesto channel, and therefore when the static water level is . below this depth it is in contact with uncontaminated soil dri GT-1, the water level is 15 feet below the base of the channel, and in GT-5 the water level is 20 feet below the base of the channel A concentration of 530 ppb was detected in GT-6 This is 50 ppb lower than in May The static water level is 13 feet below the base of the Modesto channel in this well The laboratory did not detect diesel above the 50 ppb reporting limit in either GT-3 or the Gillies domestic well In nine out of fifteen samples, diesel has not been detected in GT-3, and this represents the fifth consecutive sample in which diesel has been below the reporting limit 4.0 CONCLUSIONS The data collected in the fourth quarter of 2002 support our previous conclusion that contamination at the Gillies Trucking facility is primarily limited to soil above a depth of 55 feet When the static water level in the monitoring wells is above this depth, and particularly when it is within the Modesto channel at a depth of 45-50 feet, groundwater is in contact with diesel-impacted soil near the base of the Modesto channel and diesel becomes dissolved .in groundwater Under those conditions, diesel concentrations in groundwater have ranged from 1,000 to 190,000 ppb in wells along the axis of the channel (i e GT-10) and from 100 to 500 ppb in wells near the margin of the channel (i e GT-5) In wells beyond the channel (i e G-1 and the Barbot well), concentrations have generally remained below the detection limit, but concentrations exceeded 500 ppb on two 3