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n + 4 . 0 AIR SPARGING/VAPOR EXTRACTION SYSTEM 4. 1 Sys. em Descrilotion and ODeration The AS/VE system works by infecting clean air into sparge wells at the site These sparge wells are screened only at the bottom of the water-bearing zone so the air bubbles rise through the water-bearing zone stripping hydrocarbons from saturated soil and groundwater and transporting t h e hydrocarbons into the vadose zone The hydrocarbons are then removed from the vadose zone through a series of vapor extraction wells The vapors are then abated using an internal combustion (IC) engine A complete description of the ASIVE system installation may be found the ASE "System Installation Report" dated February 21, 2002 The system began operation on December 21, 2001 and continued operation until January 1, 2003 On May 13, 2003, ASE re-started t h e AS/VE remediation system The system is still in continuous operation at the site 4 -2 Hydrocarbon Mass. Removed During System Ope-ratioi Based on TPH-G concentrations in the influent air stream and average extraction flow rates, the AS/VE remediation system has recovered and remediated approximately 527 67 gallons of gasoline at the site The Monthly Mass Extraction Calculations are presented in Table Four This system has been highly effective in both soil and groundwater remediation On a cost per mass removed basis, the system removed 527 67 gallons of gasoline over the 18 months of operation at the site, with a calculated cost of $297 per gallon of gasoline removed This cost is over 600% more efficient than the "pump and treat" remediation system More importantly, during the AS/VE system operation there has been a significant decrease in hydrocarbon concentrations in both soil and groundwater on-site As shown in Table Two, the hydrocarbon concentrations have decreased significantly to a point where no benzene, toluene, ethylbenzene, or xylenes were detected in groundwater samples collected on-site at concentrations above the Water Quality Objectives (WQOs) listed in RWQCB Cleanup and Abatement Order #R5-2003-0713 In addition, the only oxygenate detected in any of the on-site wells above Frank's One Stop Interim Effectiveness Report — November 2003 -4-