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' Report—Remedial Action Feasibility Page 22 Cutter Lumber—Western Lift Site ' GPE Project No 102 3 • August 1,2003 t For the purposes of assessing the relative feasibility of this method, it is assumed that life of this method will require four years, and will mitigate the release to the point where a nsk-based closure will be possible The rough estimate of cost of this remedial method is ' estimated to be roughly $400,000 9.4 Vapor Extraction with Groundwater Pumping ' Past work performed at the adjacent Manna Pro site (4004 S El Dorado Street) by Groundwater Technology Inc (GTI) in 1994 documented pilot level field-testing of a remedial concept involving simultaneous vapor extraction and groundwater pumping ' This work concluded that soil vapor extraction used in conjunction with groundwater pumping is a feasible method of remediation ' The GTI report went on to propose a conceptual remedial action plan The plan proposed that 3 groundwater extraction wells and 20 vapor extraction wells be constructed to ' facilitate the extraction of gasoline In concept, groundwater would be removed via the three groundwater pumping wells in order create a groundwater depression This depression is intended to prevent the escape of dissolved-phase hydrocarbons from the treatment area As a side benefit, the small decrease in groundwater level would also expose more unsaturated zone to vapor extraction The principal remedial mechanism in the GTI proposal is vapor extraction The groundwater pumping did not materially ' depress the groundwater level and was proposed principally to prevent lateral spread of contamination due to groundwater "mounding" resulting from application of a vacuum associated with vapor extraction The GTI proposal did not include any estimate of the time needed to complete the extraction process, nor did it estimate the rate of hydrocarbon removal over the life of the ' protect The groundwater extraction data collected by GTI make it apparent, that based on the ' recent high levels of groundwater, the reduction in elevation of groundwater due to pumping would not be adequate to expose the more intensely contaminated interval (35 to 45 feet bgs) The data also seem to clearly show that it is unlikely that this method would be substantially more effective in hydrocarbon removal than vapor extraction alone, unless the groundwater surface falls rather dramatically For reasons described ' above,this remedial method does not appear to be feasible at this time 1 i ' 2937 Veneman Ave , #B240 Geo-Phase Environmental Inc Phone(209) 569-0293 Modesto, CA 95356 Fax(209) 569-0295