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3246 East Fremont Street, Stockton, California September 16, 1993 <br /> { Chevron USA Products Company Page 3 <br /> encountered during drilling using the Unified Soil Classification System (Appendix B). The drilling <br /> operation was supervised by a California registered geologist. The soil from the borings was placed in <br /> 55-gallon drums and left on site for characterization and disposal at a later date. <br /> ' The objectives of the soil borings were: 1) To deflne the vertical extent of any residual soil contamination <br /> that may have existed between the deepest tank bottom sample beneath the former 2,000-gallon <br /> Premium gasoline tank and the deepest soil sample obtained in former monitoring well MW-1, and to <br /> determine If dissolved hydrocarbons in groundwater may have remained near the source area; and 2) To <br /> remove and inspect any existing product lines and determine the extent of hydrocarbon impacted soil <br /> and groundwater, if any, that may have occurred as a result of a product line release. <br /> ' 3.3 SOIL EXCAVATION <br /> According to Chevron records, replacement piping Installed In 7985 and the septic tank were removed in <br /> 1987 during tank removal activities on site. To verify that the septic tank and product lines had been <br /> removed, Groundwater Technology personnel supervised exploratory trenching on May 4, 1993. The <br /> trenching disclosed that the replacement piping had been removed but the original product lines had <br /> ' been left In place. Exploratory trenching conducted in the vicinity of the former septic tank pit confirmed <br /> that the septic tank had been removed. Approximate locations of the exploratory trenches are shown on <br /> Figure 2. <br /> ' 3.4 SOIL SAMPLING <br /> During the drilling operations, soil samples were collected at five-foot intervals, beginning at <br /> ' approximately 5 feet below grade (BG) to the bottom of the boring. Samples were collected using a <br /> 2.5-inch outside diameter split-spoon sampler, lined with three 2-inch-diameter by 6-inch-long brass <br /> ' sample tubes. The sampler was driven 18 inches ahead of the augers at each sample point. Soil <br /> samples were field screened using a photo-ionization detector (PID). One sample from every five-foot <br /> Interval was sealed with aluminum foil, capped, taped, labeled, placed on ice in an insulated container <br /> and delivered to a State of California-certified laboratory. <br /> U'GRoUN DWATER <br /> ' 3865EAR RPr =TECHNOLOCY <br />