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-� , r ME, <br /> AIN <br /> f <br /> TAPIK C OSi1RF*�NFPORT <br /> �.•. <br /> 620 Was C'hnicr Wasp, Stockton, California <br /> Dnha Project No.40.88.596 <br /> rase 4 <br /> 2.5 Site Genlnw and Grrntnd Nater <br /> Subsurface geology at the site has been inferred from drilling eight soil borings in February 1989. During <br /> advancement or soil borings,the soils beneath the site were found to consist of clayey silt and silty clay, <br /> with a minor fine• to racdium-grained saad fraction. Ground water was encountered during drilling at a <br /> depth of 29 feet below grade. <br /> 3.0 SAMPLING AND LABORATORY TESTING PROTOCOL <br /> 3.1 Sam ling Protocol <br /> Soil samples were collected for chemical analysis immediately after tank removal. The soil sampling was <br /> directed by a Delta geologist. A brass sampli!:g tube was used to collect soil samples at both the fill and <br /> nonfill ends of each tank, approximately r feet bet-low the bottom of the tank excavation. An additional <br /> sample was collected from the northeast corner of the former tank excavation at a depth of 19.5 feet <br /> below grade. Three soil samples were collected at approximately 20-foot intervals along the,excavated <br /> t product line trenches. In February 1989,two soil boring samples were collected to determine if petroleum <br /> constituents were present in soils on the west side of the new tank excavation, and during the tank <br /> replacement work, five additional samples were collected in the new unk excavation. One soil sample <br /> each was collected beneath the waste oil tank, the sump,and the two service bay hoists located bcneL:lh <br /> the former station building(Figure 2). <br /> 3.23.2 Labomtory Analyses <br /> Soil samples retrieved from the former tank excavation, the new tank cycavatian, and the product line <br /> trenches were immediately delivered to a California-certified on-site mobile laboratory, operated by <br /> Western Environmental Science and Technology(West). Ther:.-samples were analyzed for BTEX by EPA <br /> i Method 8020,TPH by EPA Method 8015, and selected samples were submitted for analysis of organic <br /> Ems. lead. Five composite soil samples collected from the stockpiled soils were ana}y;,cd for these :tame <br /> constituents. Soil samples collected from the waste oil tank excavation, the sump,and the two hoist areas <br /> were submitted to Sequoia Analytical in Redwood City,California,for analysis of BTEX and TPH by EPA <br /> Methods 801518020,TPH (diesel) by EPA Method 8015,oil and grease by Standard Methods 503 D&E, <br /> halogenated volatile organics by EPA Method 8010, polychlorinated biphenyl (PCB), pentachlorophenol <br /> w <br /> (PCP), polynuclear aromatics (PNA),and creosote by EPA Method 8270 and 8270 "open scan*and the <br /> following metals: cadmium (Cd),chromium (Cr),lead (Pb),and zinc (Zn) by EPA Methods 7130, 7150, <br /> `^ 7420, and 7950, respectively. <br />