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. were recorded on the Well Monitor Report (Appendix A) The measurement for GT-3 was not usable, however, because the standpipe for this well was broken off and the casing was damaged The wells were purged of standing water before samples were collected Well GT-10 was not purged, because this well contained only a few inches of water Only 6 gallons were purged from GT-6 because of the low water level, the water level was drawn down during purging and the well recharged slowly Eight gallons were purged from GT-5, and between 12 and 18 gallons were purged from the two deep wells (GT-1 and GT-2) The purged water was tested for electrical conductivity and temperature, and was stored in a 55-gallon drum After purging, samples were collected in disposable plastic bailers and transferred to 1-liter amber bottles and 40-m1 vials Samples were also collected at the tap on the two domestic wells (G-1 and the Barbot well) The samples were labeled and placed into a cooled ice chest, and then shipped to McCampbell Analytical for analysis All samples were analyzed for TPH-diesel, and the samples from GT-1 and GT-10 were also analyzed for TPH-gasoline, BTEX, and gasoline oxygenates The laboratory report is contained in Appendix B 4.0 RESULTS 4.1 Depth to Groundwater Table 1 provides all depth-to-groundwater measurements and calculated groundwater elevations, . and Figure 3 illustrates the historical record of groundwater depth data for one selected well When monitoring began in 1994, the depth to groundwater was approximately 75 feet, but the water level rose continuously through 1995 to an average depth of 57 feet The level declined to below 60 feet in 1996, but then began rising again in 1997 The depth rose rapidly in early 1998 and remained between 45 and 50 feet through the first half of 1999 Since late 1999, the depth has been greater than 50 feet except for the first half of 2000 Presently, it averages 58 2 feet At this depth, it is less than 2 feet above the bottom of the shallowest well (GT-10), 3 feet below the top of the screened interval in GT-5 and GT-6, and 16 75 feet above the top of the screened interval in GT-1 and GT-2 An erosional channel is present within the Pleistocene Modesto Formation beneath the site The channel is scoured into older silt and clay deposits, making it possible to identify it in most of the wells and borings that have been drilled The depth to the base of this channel was used to map this southwest-trending aquifer sand, as described in the Problem Assessment Report The base of the channel varies from a depth maximum of between 52 and 54 feet along its axis in GT-3 and GT-10 to a minimum of less than 40 feet along its northern and southern margins Therefore, at a depth of 58 feet, the static water level is presently near the base of the silt and clay beds that underlie this aquifer 4.2 Hydraulic Gradient and Groundwater Flow Direction The calculated water table elevations were used to construct the groundwater elevation map in Figure 4 This is a very unusual map, because the elevation contours are sinuous and form a reverse "S" curve As a result, the water level appears to be highest in the vicinity of GT-8 and lowest near 3