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i TANK CLOSURF RFPCZT 620 West Charter Way,Stockton,California Delia Project No. 40-88-586 Page 5 4.0 ON-SITE. FINDINCS W 4.1 Description or Removal Process The four underground storage tanks were excavated and removed from the site:on November 14, 15239. The fuel storage tanks were triple-rinsed and purged with dry ice to reduce the risk of explosion during removal and transport. A representative of the San Joaquin County,Environmental Health Department, was present during tank removal. The tanks were transported to Erickson, Inc., in Richmond, California for disposal. µ 4.2 S611 Conditions A Delta representative was present during the excavation of the underground storage tanks to ensure all soils being excavated were contained on site,and to screen soils with a MD for total organic vapors. As soils were excavated from the former tank hole, they were screened with the PID and, based on PID readings,were separated into "clean" and "dirty" stockpiles. 4_.3 Former Tank Excavatian Samnlina Six soil samples were collected from approximately 2 feet below the base of the former tank:excavation at locations indicated in Figure 2 (sample Iocations labeled S. End Tank 1, 2, 4, and N. End Tank 1, 2, and 4). A portion of the northeast corner of the tank excavation was advanced to a depth of I9.5 feet below grade and a sample was collected. Each of these samples was analyzed for the constituents listed in Section 3.2. A summary of the laboratory analyses is presented in Table 1. Copies of certified laboratory reports are prey:nted in Appendix A ' As shown in Table 1, the concentrations of TPH (as gasoline) in soil samples collected from the former tank excavation ranged front 1.4 parts per million (ppm) in the southwest portion of the excavation to >. 7,100 ppm at a depth of 19.5 feet in the northeast corner of the tank excavation.