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June 25, 1991 ARCO Service Station 760, Lodi, California Resuits of analyses of soil samples collected. from the proposed tank cavity are presented in Table 2. Concentrations of TPHg were below detection limits; BTEX concentrations below 1.0 ppm were detected.. Results of analyses of the liquid collected from inside the waste-oiI tank and the soil sample collected under the tank are presented in Table 3. Hydrocarbons were not detected in this soil sample. Total concentrations of metals detected were below the soluble threshold limit concentrations. Concentrations of 170 parts per billion (ppb)TPHg, 1,900 ppb TPHd,and 7.7, 8.8, 1.2, and 12 ppb BTEX, respectively, were detected in the liquid from tank T8. Vapor-Extraction Test On June 13, 1991,borings B-9 through B-11 were drilled and converted to vapor-extraction wells VW-1 through VW-3. A vapor-extraction test was conducted on June 14, 1991, to evaluate whether remediation of residual hydrocarbons in native soil underlying the site is feasible by vapor extraction. Details and results of our work will be presented in a1etter report that is ir!preparation. Appropriate details arc summarized below. - Applied GeoSystems used an internal combustion engine to collect vapor samples from vapor extraction wells VW-1, VW-2, and VW-3. The engine was initially operated for approx;mately 2 hours before a sample was collected. Vacuum at the extraction well;flow rate, and vacuum at the observation wells were monitored every 30 mir.-ites. The distances between VW-3 and VW-2 and VW-1 are 28.2 and 34.9 feet, respectir sly. The distances ` between VW-2 and VW-1 is 31.7 feet. Vapor samples were analyzed for TPHg using modified EPA Method 8015 and BTEX using ' EPA Method 8020. Copies of the Chain of Custody Records an: results of laboratory analyses of the vapor samples are attached. z Vapor Fxtraction Test Results Results of laboratory analyses for rir samples taken during the vapor-extraction test are summarized in'fable 4. After system stabilization, the highest vacuum observed in VW-2 was 0.14 inches of water at a distance of approximately 28.2 feet from VW-3, whit VW-3 was undergoing a vacuum pressure of 5.0 inches of water column and a flow rate of approximately 33 cubic feet per minute (cin#). The results of laboratory analyses of the vapor samples indicated TPHg concentrations from VW-3 were below the detection limit, of 5.0 milligrams per cubic meter(mg/m3), 2,900 mg/m3 from VW-2, and 980 mg/m3 from VV4'-1. 38048 S 3