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Canepa's Car Wash(Pacific Avenue) Problem Assessment Report and Corrective Action Plan ' Page 13 potentially viable alternative in terms of both effectiveness and response time. Vendor studies have indicated that chemical oxidation (i.e. ozone injection), can proceed very quickly, with up to 90% destruction in a matter of minutes. However, ozone reactions are most effective in systems with acidic PH, and the process requires closely-spaced delivery points (many air sparging wells). However, the use of ozone can also provide an additional source of dissolved oxygen, enhancing natural attenuation. If the intent is the simple enhancement of natural attenuation by increasing dissolved oxygen, mechanisms other than ozone may be more effective. Air sparging is highly suspect in the heterogeneous soils of the site. The presence of intermittent clay layers could significantly reduce the radial effectiveness of the air sparging and groundwater circulation, and could lead to short-circuiting. Pump and treat by itself could take as long as natural biodegradation due to the suspected high petroleum hydrocarbon concentrations in the soil below the groundwater table. However, the soil vapor extraction system appears to have been successful in removal of the soil contamination above the groundwater. Consequently, the pump and treat method could be effective in removing and treating the contamination in the groundwater, and in creating a sufficient drawdown that soil vapor extraction could remove contaminants from the soil below the current groundwater table. ' 7.3 COST EVALUATION Natural attenuation and enhanced biodegradation can be very inexpensive. Consequently, even though ' these alternatives are not proposed as the only alternative because they are not expected to be sufficiently effective, they can be used in conjunction with any other alternative. As the project progresses, the use of nutrients or oxygen sources will continue to be evaluated. Chemical oxidation in the form of ozone injection has been shown to be effective where the ozone can contact a sufficient volume of groundwater. The Federal Remediation Technologies Roundtable (FRTR) ' estimates the cost of chemical oxidation between $0.10 to $10.00 per 1,000 gallons. With an estimated plume area of about 'A acre, a thickness of 20 feet, and a porosity of 25%, we will need to treat about 375,000 gallons. On the per/gallon basis, at the upper end the estimate is less than $4,000. However, in ' U.S. EPA's Field Applications of In Situ Remediation Technologies, the cost for ozone equipment ranged from $35,000 to $90,000, excluding well installation. ' Air sparging would use much of the same equipment as ozone, including an air injection system and injection wells. While soil vapor extraction is not necessarily indicated with ozone injection, it is expected that some air stripping will occur and soil vapor extraction could effectively augment the ' contaminant removal and treatment. In addition, the soil vapor extraction equipment is already in use on site, so the additional costs would be for additional extraction wells and operation of the system. FRTR estimates air sparging at $150,000 to $350,000 per acre. For an estimated '/4 acre site, the estimate would be $40,000 to $90,000. The groundwater pump and treat system costs are highly dependent on the cost of treatment. Although it is expected that liquid-phase carbon adsorption will be most cost effective, Condor will evaluate additional technologies such as electro-oxidation and bioreactors as alternatives. Similarly, it may be shown that air stripping and carbon polishing may be the most cost effective, especially considering the existing vapor treatment system on site. The cost range for pump and treat with carbon adsorption ranges from $1.20 to $6.30 per 1,000 gallons. Using the estimated gallonage noted above, this would result in an • } 4M� CONDOR