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Working To Restore Nature ' Report on Vapor Extraction Test January 29, 1993 Coca-Cola Former Distribution Facility, Stockton, California 5400601 ' for the remaining observation wells, the screened interval overlap was at least 20 feet, which is more than adequate for good vacuum impact The induced vacuums measured in the ' observation wells are considered to be low The correlation between distance from extraction well VEW-1 and vacuum impact in observation wells was good, but distance alone is insufficient to account for the low induced vacuum readings As discussed below in "Field Vapor Monitoring", an increase in subsurface oxygen content was a function of increased flow rate in all wells, except VEW-1 VEW-1 had the highest flow rate, as reported in Table 3, but a low oxygen content The reason for this is unknown, but may be due to differential flow through a subsurface anaerobic sandy channel or may be due to anaerobic organic material such as peat, which allows high air flows but depletes subsurface oxygen ' Field Vapor Monitoring Vapor concentrations, oxygen concentrations, and lower explosivity limits (LEL) were monitored during testing and sampling at each well with a Bacharach 503A explosimeter Subsurface oxygen concentrations ranged from 2% to 4% in extraction well VEW-3, from 5% to 10% in extraction well VEW-1, and in the observation wells oxygen ranged from 4% in VEW-4 to 14% in VEW-8 Ambient air generally contains about 21% oxygen Wellhead oxygen concentrations are reported in Table 3 For all wells, except VEW-1, an increase in air flow was accompanied by a corresponding increase in soil vapor oxygen concentration ' The correlation was linear when % oxygen was graphed as a function of air flow rate The explosive range for gasoline is 1 417o to 8% (14,000 parts per million by volume [ppmv] ' to 80,000 ppmv), with 14,000 representing the lower explosive limit (LEL) and 80,000 the upper limit (UEL) (where 14,000 ppmv represents about 63,000 mg/m3 and 80,000 ppmv represents about 360,000 mg/m3) Outside this range the gasoline/air mixture is either too lean or too rich for explosive conditions to develop Field vapor concentrations are reported in Table 2, and are considered order of magnitude only and are subject to the results of laboratory analysis Field recorded vapor concentrations ranged from 1,500 ppmv to greater ' than 10,000 ppmv, with the higher concentrations being recorded in VEW-3 The highest measurement on the LEL meter was 35% of the LEL which is below the explosive range iDISCUSSION Effective Radius of Influence Utilizing induced vacuum and distance measurements obtained during the VET, an effective radius of influence was estimated for the vapor wells at the site The effective radius of influence has been defined as the radial distance from a vapor extraction well at which 12