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' -S- TANK CLOSURE REPORT—BEACON STATION #419 2350 Waterloo Road, Stockton, CA AMV Project No 19011 03 ' 4.0 OVEREXCAVATION AND ADDITIONAL SOIL SAMPLING ' The site was visited on October 26, 1993, to perform overexcavation of the former tank basal area. Soil samples were collected at locations designated by the San Joaquin County ' Environmental Health Representative (Figure 4) The overexcavation was performed by Walton Engineenng Soil samples were collected from locations selected to determine the vertical extent of hydrocarbon constituents in the soil underlying the site. The soil samples were submitted to a California-certified laboratory for analysis of BTEX and TPHg One soil sample (T1A) was ' analyzed for total and soluble lead Analytical results from the October 26, 1993, overexcavation sampling are compiled in Table 1 Copies of certified analytical reports are ' presented in Appendix C. Soil samples T1A through T5A were collected at depths ranging from 22 to 30 feet below the ground surface on October 26, 1993 Petroleum hydrocarbon constituents were detected in each of these samples except T5A, which was collected at 22 feet below the ground surface Xylenes at a concentration of 0.029 mg/kg were the only constituents detected in the soil sample ' collected from location T4A at a depth of 22 feet below grade Concentrations of TPHg in the remaining samples collected from the former tank basin on October 26, 1993, ranged from 330 mg/kg to 2,500 mg/kg In soil samples collected from locations T3A and T1A, respectively 5.0 STOCKPILED SOIL Soil that was removed during excavation of the USTs and product lines was stockpiled on site Approximately 950 cubic yards of soil were generated between October 22 and 26, 1993 Two hundred and fifty cubic yards of soil were excavated prior to the UST removal, and approximately 700 cubic yards were removed during the clean out and overexcavation of the ' tank basin and the former pump islands Four soil samples for every 50 cubic yards of stockpiled soil were collected (unless otherwise required for disposal) for analysis of BTEX and TPHg. Each set of four soil samples was then submitted to the laboratory for compositing Analysis of stockpile soil samples collected October 22 and 26, 1993, contained TPHg concentrations ranging from nondetectable levels to 3,000 mg/kg Analytical results are compiled in Table 3. Copies of certified analytical reports are presented in Appendix D One composite soil sample collected from the stockpile on October 26, 1993, was also submitted for analysis of Halogenated Organic Volatiles using Environmental Protection Agency Method 8010 This sample was also tested for analysis of the following metals Arsenic, Barium, Cadmium, Chromium (Total), Chromium (Soluble), Cobalt, Copper, Lead, Nickel, Mercury, and Zinc Results of composite soil sample analyses are compiled in Tables 4 and 5, respectively ' RPr020 ECD