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• Soil Vapor Extraction Test Results ARCO Facility 2186 Stockton, California Page 4 following results were developed based on our evaluation of field data and analytical results of the soil vapor samples • Soil vapors extracted from VW-1S contained TPHG and benzene concentrations (highest) of 4,320 milligram per cubic meter (mg/m) and 76 2 mg/m3, respectively • Soil vapors extracted from VW-2S contained TPHG and benzene concentrations of 2,740 mg/m3 and 33 2 mg/m3, respectively • Soil vapors extracted from VW-3S contained TPHG and benzene concentrations of 1,370 Mg/m3 and 8 51 mg/m3, respectively • The thermal oxidizer achieved greater than 99% destruction efficiency during the SVE tests, and therefore was to compliance with SJVUAPCD guidelines Radius of Influence The ROI generated by SVE is typically determined by measuring the steady-state pressure distribution around the extraction well The effective ROI has been defined as the radial distance from a vapor extraction well at which recorded vacuum levels suggest that subsurface air flow occurs and is presumed to be sufficient for remediation Air- modeling studies conducted by others suggest that the distance from the extraction well at which one percent of the applied wellhead vacuum occurs can be interpreted as an effective ROI (Chevron, 1991, P C Johnson, 1988) This method is based on theoretical model predictions, which project that roughly ninety percent of the total air extracted from the well flows through soils within the ROI when a one percent cutoff is used For the purpose of this study, the ROI of an SVE well is defined as the distance from the SVE well at which one percent of the applied wellhead vacuum occurs • SVE at 10 cfrn @ 100 "WC on well VW-1A produced a ROI of 34 feet • SVE at 10 cfm @ 80"WC on well VW-2A produced a ROI of 34 feet • SVE at 9 cfm @ 50"WC on well VW-3A produced a ROT of 45 feet Adequate monitoring points with available screen intervals (see Table 1) in the vadose were not available to produce vacuum versus distance plots, which are also commonly used to estimate ROI Mass Extraction Rates Initial hydrocarbon mass extraction rates for VW-1S, VW-2S and VW-3S are calculated to be 3 88, 2 46, and 1 10 pounds per day, respectively These rates are based on the