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June 1, 1988 AGS Job No. 038032-2 <br /> UNOCAL Service Station No. 6981, Stockton, California <br /> o Excavate two soil borings in locations near the boundaries <br /> of contamination on the basis of the results of the soil <br /> vapor survey and one soil boxing near the suspected source <br /> I') of contamination. The borings will be drilled to 20 feet <br /> below the ground-water surface, or approximately 50 feet <br /> below the ground surface and will be used for the <br /> installation of monitoring wells. <br /> o Collect and classify relatively undisturbed soil samples <br /> +� taken at 5-foot intervals in the soil borings. <br /> o Construct three ground-water monitoring wells in the <br /> boreholes. The wells will be constructed usa.ng 2-inch <br /> inner-diameter polyvinyl chloride (PVC) casing. <br /> o Develop the wells and collect ground-water samples. <br /> o Analyze selected soil and ground water samples for gasoline <br /> product constituents in a laboratory certified by the State <br /> of California. <br /> a Evaluate the local ground-water gradient by surveying the <br /> top of each well casing, measuring static ground-water <br /> depths in the wells, and calculating the relative elevation <br /> of the ground-water surface in each well. <br /> o Interpret field and laboratory data to evaluate the extent <br /> of contamination. <br /> o Describe subsurface conditions at the site as revealed in <br /> the borings including discussions of the geology, <br /> hydrogealogy, and ground-water usage in the area. <br /> ". � o Prepare a report summarizing our findings, conclusions, and <br /> recommendations. <br /> One of the proposed monitoring wells will be located within the <br /> vicinity of the highest hydrocarbon concentrations based on soil <br /> samples analyzed from 19-feet below grade during the initial <br /> excavation in order to evaluate contaminant levels below the <br /> --- -- - <: - - -----suspected--source__of_contamination. This well will be used to <br /> 6 <br /> 4' Alaplied. Ge0Systems <br />