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PRETANK CLOSURE SITE ASSESSMENT <br /> 3725 Tracy Boulevard, Tracy, CA <br /> Delta Project No. M-89-012 <br /> Page 5 <br /> prior to hookup to <br /> public sewer in 1974. Further, if it is presumed, the site contained <br /> a septic system. It is unknown whether the system was removed or abandoned in place. <br /> LO -PROE05ED SOIL BORINGS <br /> This section describes the proposed assessment, including the depth and distribution <br /> of exploratory soil borings. The methods used to drill and sample the borings, <br /> analytical procedures, quality assurance plan, and the site safety plan are contained <br /> in Appendix C. <br /> 3.1 Exaloratory&ll Barings <br /> A total of ten soil borings will be advanced within the properties of the site. Four soil <br /> borings will be advanced adjacent to the existing underground storage tank location <br /> (Figure 3). Four soil borings will be advanced in the vicinity of the proposed new tank <br /> installation location, and two other soil borings will be located adjacent to the <br /> dispensing line locations. <br /> All soil borings will be advanced using a 7.5- to 8-inch-diameter hollow-stem auger. <br /> Samples will be collected in a California modified split-spoon sampler. Appendix C, <br /> describes the drilling and sampling techniques to be used. Soil samples will be <br /> collected at vertical intervals of 5.0 feet. Borings will be advanced to a minimum depth <br /> of 20 feet, or until three consecutive soil samples show nondetectable levels of <br /> contamination. Soils will be screened with a PID, as described in Appendix C to <br /> determine organic vapor content. Level of contamination will be considered <br /> nondetectable for organic vapor content compatible with background levels. A "clean" <br /> sample will be submitted for Iaboratory analysis to verify the field determination. <br /> 1.2 $oil Sample Collection and Screening <br /> Soil samples will be recovered using brass sample tubes within a California modified <br /> split-barrel sampler. A brass sample tube will be capped and preserved according to <br /> accepted EPA procedures for possible chemical analysis. A sample adjacent to the brass <br /> tube will be sealed in a glass jar. All soil samples collected in glass jars will be <br /> brought to the same temperature and screened for total organic vapors utilizing the PID. <br /> Appendix C describes the soil screening procedure. Based on this information, soil <br /> samples will be selected for chemical analysis. <br />