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i WA======AZ June 25, 1991 ARCO. Service Station 760, Lodi, California Results 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-oil 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 imit cos:entrations. Concentrations of 170 parts per billion(ppb)TPHg, 1,900 pp sh i 7.75`8.8, 1.2, and 12 ppb BTEX, respectively,were detected in the liquid from tank T8. r Vapor-Extraction Test On June 13, 1991,borings 13-9 through B-11 were drilled and converted to vapor-extraction wells VW-1 through VW-3. A vaporextraction test was conducted on June 14, 1991, to n of residual hydrocarbons in native soil underlying the site,is evaluate whether remediatio results of our work will be presented in a letter feasible by vapor extraction. Details and 3 report that is in preparation. Appropriate details are summarized below. ._� Applied.GeoSystems used an internal combustion engine to collect vapor samples from , VW-2, and VW-3. The engine was initially operated for vapor-extraction wells VW-1 approximately 2 hours before a sample was collected. Vacuum at the extraction well,flow rate,and vacuum at the observation wells were monitored every 30 minutes. The distances between VW-3 and VW-2 and VW-1 are 28.2 and 34.9 feet, respectively. The distances between VW-2 and VW-1 is 31.7 feet. Vapor samples wets analyzed for TPHg using modified EPA Method 8015 and BTEX using EPAMetad 8020.. Copies of the Chain of Custody Records and results of laboratory analyses of the vapor samples are attached. Vapor-Ex-traction Test Results Results of laboratory analyses for air samples taken during the vaporextraction lest are summarized in Table 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, while VW-3 i was undergoing a vacuum pressure of 5.0 inches of water column and a flow rate of approximately 33 cubic feet per minute (cmf). Tho results of laboratory analyses of the t 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 VW-I." 3801E-5 4. x r p