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C A M B R I A Ms. Lori Duncan September 9,2005 vacuum of the vapor extraction wells observed during pilot testing. The treatment device is determined by the anticipated influent flow rate, hydrocarbon concentration, air quality requirements,and operating duration. AS is a remedial technology whereby air is injected into the saturated zone to remove volatile contaminants by stripping them from water, transferring them to the vapor phase, and removing the vapors by SVE. The technology is designed to operate at relatively high air flow rates (greater than 2 cubic feet per minute per injection point) in order to cause volatilization. SVE is most effective in moderate to high permeability soils. AS is not specifically aimed at stimulating biodegradation, although enhanced biodegradation may be realized as a secondary effect. AS © must operate in tandem with an SVE system that captures the volatile contaminants stripped from the saturated zone. Equipment required to implement AS would include a compressed air source (air compressor), compressed air conveyance piping, specifically designed AS wells, and a down-well delivery system (piping and/or stingers). The air compressor would be sized based on the number of injection points, pressure losses through the delivery system, and minimum pressure and flow delivery at the injection depth. Feasibility and Cost-Effectiveness: Design, permitting, and installation of an SVE/AS system at the subject site would cost an estimated $175,000 to $200,000. This estimate is based upon installing four additional SVE wells and four AS wells, installing underground piping, constructing a treatment compound, and installing the required equipment, including a new thermal oxidizer. Operational cost of an SVE/AS system for the first year is estimated at $60,000. SVE/AS operation is assumed for a minimum of 3 years and a maximum of 5 years to meet soil clean-up levels. Operational costs would decrease over time as influent concentrations and mass removal rates decrease and become asymptotic. As vapor concentrations decrease, a thermal oxidizer could be replaced by a more fuel-efficient catalytic oxidizer, and later by vapor- phase GAC adsorption vessels. The average annual operational cost is estimated at $40,000 per year SVE is likely to be somewhat effective at reducing source area hydrocarbon mass in the vadose zone. However,SVE effectiveness at the site would be limited by the high proportion of clay and silt (low permeability) soils above the current water table, and SVE would not directly treat groundwater and saturated soils. SVE with AS may be significantly more effective than SVE alone, since it also volatilizes and removes hydrocarbon constituents from groundwater and saturated soils beneath the site. However, as with SVE, AS effectiveness may be limited by the low permeability soils below the water table. Once concentrations appear to be approaching asymptotic conditions, pulsed operation may be needed to assess soil vapor and groundwater concentration rebound. To verify soil clean-up, confirmation soil borings would be required. The cost of four confirmation soil borings is estimated at$10,000. 15