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9 0 <br /> Division (San Joaquin County). Sampling activities were performed in accordance <br /> to the UST closure permit provisions imposed by the San Joaquin County. See <br /> Section 2.4 (Sampling and Analysis) for details. <br /> Upon exposure of the UST, the atmosphere inside the tank was monitored for <br /> combustible vapors using an explosimeter, which was calibrated against methane. <br /> No liquid was present in either the tank or the piping. The appurtenances were <br /> removed from the tank and openings were capped, except those necessary to <br /> purge and inert the tank. The explosimeter probe was inserted into the tank without <br /> touching the surface of the walls. The tank was inerted by using dry ice at 30 <br /> pounds per 1,000 gallons of tank volume to lower the oxygen level below five <br /> percent. <br /> The UST was removed on August 28, 1995. The tank excavation was about 13 <br /> feet deep. Removal activities were supervised by Michael DeKlotz, Bert Hikichi, <br /> and Robert McClellon. Robert McClellon also identified sampling locations. See <br /> Section 2.4 (Sampling and Analysis) for details. No obvious holes were found at <br /> the side or bottom of the UST removed. There was also no evidence of soil <br /> staining. <br /> Groundwater was not encountered in the excavation during the UST removal. <br /> 2.4 SAMPLING AND ANALYSIS <br /> Soil samples were collected on two different occasions. Nine samples were <br /> collected on August 28, 1995, after the UST was removed. These samples were <br /> collected from the bottom of the excavation, at the bottom of the pipe trench, and <br /> from the soil stockpile during the field activities (see Figure 3). Seven additional <br /> confirmatory samples were collected on November 8, 1995, prior to backfilling the <br /> excavation. These samples were considered by San Joaquin County as duplicates <br /> of seven of the original nine samples collected on August 28, 1995 (see Figure 4). <br /> Sampling information is provided in Table 1. <br /> On August 28, 1995, four soil samples were collected at a depth of about two feet <br /> from the bottom of the UST excavation. One of the four samples was a quality <br /> control (QC) sample. No quality assurance (QA) samples were collected per <br /> instructions from the USACE. One soil sample was from the pipe trench, where a <br /> dispenser used to be and four discrete samples from the excavated soil stockpile <br /> were collected and shipped to CKY, Inc. Analytical Services (CKY Lab) in Torrance <br /> for analysis. <br /> The first set of soil samples, collected on August 28, 1995, were analyzed for total <br /> petroleum hydrocarbons as diesel by Modified EPA Method 8015 (TPH-d), TPH as <br /> gasoline by Modified EPA Method 8015 (TPH-g), total lead by EPA Method 7421, <br /> and benzene, toluene, ethylbenzene, and total xylenes (BTEX) by EPA Method <br /> 2-2 <br />