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11 <br /> TREADWELL & ROLLO <br /> o converted the exploratory boring into a monitoring well (MW-1) <br /> o developed the monitoring well (MW-1) and collected a groundwater sample <br /> o analyzed one soil sample and one groundwater sample for total petroleum <br /> hydrocarbons as diesel (TPHd) and benzene, toluene, ethylbenzene, and xylenes <br /> (BTEX) <br /> o reviewed and assessed the analytical results and prepared this report. <br /> 4.0 FIELD INVESTIGATION <br /> A boring was drilled in the presumed downgradient direction from the former storage <br /> tank excavation (Figure 2) and converted into a monitoring well (MW-1) The location <br /> of the well was based on the analytical results from our previous investigation Gregg <br /> Drilling & Testing, Inc of Pacheco, California, performed the drilling and well <br /> installation on 29 September 1993, under the direction of Treadwell & Rollo, Inc. <br /> The borehole was advanced using a truck-mounted drill ng equipped with six-inch- <br /> diameter, hollow-stem augers. It was drilled to a depth of approximately 21 feet .All <br /> augers were steam-cleaned prior to use, and the sampling equipment was cleaned <br /> between sampling intervals with a tnsodiuin phosphate solution and nosed with clean <br /> water All soil cuttings and purged groundwater were placed in 55-gallon drums which <br /> were sealed, labeled, and stored onsite <br /> 4.1 Subsurface Soil Sampling <br /> The soil samples were obtained using a California Modified, split-spoon sampler with an <br /> outside diameter of 2 5 inches The split spoon sampler was lined with clean, six-inch- <br /> long, two-inch-diameter, stainless steel tubes The sampler was driven with a 140-pound <br /> 3 <br /> 11070707 PJC 18 November 1993 <br />