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. Boring GT-11 was grouted to the surface immediately after drilling on March 22 The cuts Ings from both bonngs were stored on plastic sheeting near monitor well GT-6, pending laboratory analysis and approval from the San Joaquin Valley Air Quality Control District to aerate the soil 23 Groundwater Monitoring Groundwater monrtonng took place on March 22 The wells were opened and allowed to equalize with atmospheric pressure before water depths were measured The depth to groundwat rr in each well was measured with a Solinst water level meter and the measurements were recorded on the Well Monitor Report (Appendix B) A Gr uudfos Readi-flo 2 groundwater pump was then used to purge 15 gallons from GT-3 and 20 gallons from GT-1, GT-2, GT-6, and GT-10 Conduc ivity, pH, and temperature were measured during purging at 5-gallon intervals, and the readings were recorded on the Well Monitor Report The pump was decontaminated with TSP solution between wells, and the water was stored in 55-gallon drums near GT-6 Because of slow rec large and binding of the pump against the well casing, GT-5 was not purged In order to avoid upsetting the neighboring property owner, GT-9 was sampled but not purged w�a - , -Yj j n'51j % NL ` , , After purging,water samples were collected in disposable plastic bailers and placed in stei ilized 40- ml vials and 1-liter amber bottles The samples were placed in a plastic cooler, iced, and .hipped to McCampbell Analytical in Pacheco, California for analysis The samples were analyzed for TPH- gasoline,TPH-diesel, BTEX,and MTBE Monitor well GT-10 was surveyed into the existing gnd of wells on March 25, and a groundwater gradient map was constructed However, the data provided by the new well greatly altered the appearance of the gradient map and did not provide a unique and conclusive picture of thf gradient Therefore, all of the wells were re-surveyed on April 9, water depths were re-measured, and revised gradient maps were prepared The results are discussed thoroughly in section 3 6 3.0 RESULTS 3.1 Subsurface Stratigraphy Figure 3 summarizes the lithology of the shallow stratigraphic units underlying the site Two geologic formations are present Each formation contains several lithologic units th it can be correlated from boring to boring 3.1.1 Modesto Formation The upper several units are part of the Modesto Formation The upper part of this formation consists of 33 feet of reddish brown silt White calcareous veins or soil fractures and root soles may be present in this bed between the depths of 15 and 20 feet A bed of light reddish brawn, silty, fine-grained sand within the silt bed thins from about 7 feet in thickness to less than 2 feet in 4