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I I07 November 2003 AGE-NC Project No 98-0492 Page 8 of 9 adjusted to compensate for site conditions during a pilot test, based on dissolved concentration reaction to the sparging,ground water flow direction changes and to reduce mounding of the ground water were necessary 6 2 1 Feasibility Testing An ozone sparging pilot test has not been performed at the site Data from soil samples collected at the site indicate that poorly graded sands and silty sands are present in the water bearing zone impacted with MTBE The site stratigraphy has poorly graded sands and silty sands that typically possess hydraulic conductivity values that are favorable for air sparging and ozone infection via air-sparging Due to the readily higher vapor pressure of MTBE, low Henry's Law Constant and ' MTBE's higher aqueous solubility or the tendency to remain dissolved,the in-situ treatment should be an effective remedial alternative In other words,treatment should be conduct in the ground water media(soil/water) 6 2 2 Duration ' Sufficient data is not available to accurately predict the duration necessary to mitigate a site using ozone sparging as the remedial alternative Mitigation duration is site specific,therefore apilot study must be performed at the site before any predictions can be made The reduction efficiency should be based on in-situ dissolved oxygen measurement,groundwater sampling and MTBE-concentration trend analysis over the entire sparging time frame 6 2 3 Cost Costs for installation of an ozone system typically ranges from $25,000 to $30,000, including the ' installation of sparging wells and underground piping Based on an operational period of 12 to 24 months, costs for the entire project would likely be between $45,000 and $160,000 7.0. RECOMMENDATIONS FOR REMEDIATION OF HYDROCARBON- IMPACTED GROUND WATER ' AGE believes that an in-situ method or remediation would be more effective in both cost and performance over a"pump and treat"method AGE recommends a six month ozone sparging pilot test be performed at the site as depicted in Figure 9,to determine the effectiveness of ozone sparging • as a remedial alternative and if demonstrated modify the scope of work to perform continual remediation utilizing the in-situ remedial method Advanced GeoEnwronmental,inc I