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September 12, 1991 • ARCO Station No 760, Lodi, California The location of these wells, as well as other pertinent site features, are shown on the Generalized Site Plan, Plate 2. Testing was initiated on VW-3 with wellhead vacuum, flow rate, organic vapor concentration, temperature and vacuum monitored and recorded every 30 minutes. This same procedure was then followed on well VW-2 and then on well VW-1 Upon the completion of testing for each well, RESNA used the I C. engine to collect influent vapor samples. The engine was operated for approximately two hours on each well before samples were collected Distances between the wells are 28 2 feet (VW-2 to VW-3), 317 feet (VW-2 to VW-1) and 34 9 feet (VW-1 to VW-3) r RESNA initiated a Chain of Custody Record that accompanied the vapor samples to a State-certified laboratory. We followed chain-of-custody protocol throughout field and laboratory procedures The samples were analyzed at Sequoia Analytical in Concord, California (Hazardous Waste Testing Laboratory Certificate No 145) for benzene, toluene, total xylene isomers,and ethylbenzene by modified Environmental Protection Agency(EPA) Method 8020 and for total petroleum hydrocarbons reported as gasoline (TPHg) using modified EPA Method 8015 The results of laboratory analyses for the vapor samples are summarized in Table 1 Copies of the Chain of Custody Records and results of laboratory . analyses of the vapor samples are attached RESULTS Monitoring data and results of laboratory analyses for vapor samples taken during the VET are summarized in Table 1 Final vacuum readings recorded from the wells ranged from 0.04 inches of water at VW-1 (extracting from VW-2 at 22 cubic feet per minute (cfm), distance = 317 feet) to 0 12 inches of water at VW-2 (extracting from VW-3 at 33 cfm, distance = 28 2 feet) Vacuum data obtained from observing well VW-1 while extracting from well VW-3 and from observing well VW-1 while extracting well VW-2 appears to have been influenced by the presence of the tank backfill zone The vacuum measurements obtained from observation wells VW-3 and VW-2 are best suited for use in predicting vapor extraction system specifications The results of laboratory analyses of the'vapor samples indicated TPHg concentrations from -" well VW-3 below the detection limit of 5 0 milligrams per cubic meter (mg/m3), 2,900 mg/m3 from well VW-2, and 980 mg/m3 from well VW-1 0912CCAR 38M-062