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C A M B R I A Ms.Lori Duncan November 18,2005 vapors will pass through an entrainment separator to remove groundwater from the vapor stream. A liquid transfer pump will route the extracted water to a 500-gallon transfer tank for temporary on-site storage. Soil vapors will leave the separator,pass through the liquid-ring pump,and enter the oxidizer to be treated. The Solleco unit is all-electric and only capable of operating in catalytic mode, which is appropriate for the anticipated long-term influent vapor concentrations. Thermal mode is the most efficient treatment method for influent vapor concentrations of approximately 2,000 parts per million by volume (ppmv) or greater, while catalytic mode is generally the most efficient treatment method for influent concentrations between 200 and 2,000 ppmv. The proposed © equipment is considered best available control technology (BACT). BACT is defined as attainment of set destruction efficiencies corresponding to set influent concentration values. The Solleco unit will be operated to ensure attainment of the following required destruction efficiencies: >98.5% if inlet volatile organic compound (VOC) concentration >2,000 ppmv; >97% if inlet VOC>200 to<2,000 ppmv; >90%if inlet VOC<200 ppmv. Groundwater Disposal: Two primary options for disposing of extracted groundwater exist for the proposed DPE system: off-hauling or discharging to the sanitary sewer. The off-hauling option would consist of capturing the extracted groundwater in a temporary storage tank and coordinating vacuum trucks to routinely pump out the tank and haul the groundwater to Shell's Martinez refinery for disposal by recycling. The sanitary sewer discharge option would consist of obtaining a wastewater discharge permit from OMI-Thames Water Stockton, Inc. (OMI) to authorize the discharge and installing a groundwater treatment system to meet the conditions of the wastewater discharge permit. Through past experiences,Cambria recognizes that discharging treated groundwater in compliance with an OMI wastewater discharge permit can be cost prohibitive due to their stringent MTBE and TBA discharge limits. However, MTBE and TBA concentrations at the subject site are very low,and it should not be difficult to treat to the required levels. To determine the cost-effective option for extracted groundwater disposal, Cambria estimated costs for off-hauling untreated groundwater and disposal to the sanitary sewer. Table A presents the additional costs associated with these options. 8