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Thermal and or catalytic oxidation destroys vapors by using heat to oxidize the compounds to 16 carbon dioxide and water Heated catalyst beds can enhance the process for certain compounds Thermal technologies are most efficient treating higher concentrations of compounds at high air flow rates At lower concentrations they are less cost effective due to the requirement of an outside fuel source to maintain heat in the system. Due to the low-range flow rates observed during the SVE pilot test, the GAC vapor treatment method would be most practical. The SVE pilot test determined that vapors can effectively be extracted from the soil, without pulling the groundwater up into the well, with a vacuum of 4 psi (110 inches water). An air flow rate of approximately 24 cfm was observed from the extraction well at this vacuum. The cost estimated for in-situ vapor extraction, including emission control using GAC, ranges from $130,000 to $150,000 assuming one year of operation Each additional year of operation will add approximately $50,000 to the project cost. Assuming a total of two years of operation, the estimated cost would be $180,000 to $200,000 5.3 In-Situ Bioremediation Bioremediation of petroleum hydrocarbons can be accomplished by infecting nutrients and � acclimated bacteria into the soil matrix The moisture and pH levels of the soil are controlled and the soil is aerated through infection of oxygen, air, or hydrogen peroxide In addition, an air stream can be pulled through the soil matrix to assure even distribution of the nutrients and oxygen necessary for the survival of the bacteria Surfacants can be added to enhance the solubility of the fuel hydrocarbon The microorganisms break down and consume chemicals in the soil. Products of the reaction include carbon oxides and water. After the chemicals have been consumed, the nucroorganism population decreases to natural background levels due to the lack of a food source Collection of leachate may be required. Capital and maintenance costs for an in-situ vadose zone bioremediation system are generally higher than soil vapor extraction systems, due to operating complexities involving water and nutrient introduction, hydrogen peroxide infection, and downgradient migration control of water, nutrients and bacteria To evaluate the applicability of bioremediation for specific site conditions, treatability studies must be performed, and the costs for such a study would be approximately $30,000 Capital costs for the installation of water and nutrient injection systems would be approximately $125,000, and a downgradient groundwater extraction and recirculation system at approximately $75,000 Total initial in-situ bioremediation capital costs are estimated to be approximately $230,000 In addition, operation, maintenance and management costs are ' estimated at $50,000 to $75,000 per year. This estimate does not include daily operating costs for nutrient and hydrogen peroxide supply, which would vary depending on site conditions, and does not address the complexities of permitting such a system. �' 1110lcd3 17