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The site has experienced a dramatic downward trend in hydrocarbon a n d <br /> • oxygenate concentrations since the remediation system was turned on In <br /> monitoring well MW-2, the most severely contaminated well on site, the <br /> concentrations of hydrocarbons and oxygenates have dropped an order of <br /> magnitude and have remained low until a recent reversal in the downward <br /> ' trend, see Table Two and the graphs of the individual wells ASE believes <br /> the slight increase in concentrations in the last two sampling events are <br /> ' due to the recent failure of the ozone delivery tubing ASE expects to see <br /> a return to the downward trend in the next several sampling events <br /> ' 5 . 0 PROPOSED REMEDIATION STRATEGY FOR THE NEXT SIX <br /> MONTHS <br /> iASE believes that the system should remain operational for another period <br /> of 6 months Groundwater sampling of the six monitoring wells should <br /> ' occur on an 8-week sampling frequency A second evaluation report <br /> should be prepared during the month of September 2003 detailing the <br /> system's performance and provide recommendations for future remedial <br /> activities <br /> At this point in time, ASE believes that continued measurement of DO in <br /> 1 the on-site monitoring wells is no longer necessary It is obvious, by <br /> reviewing the analytical data, that the remediation system is working, <br /> 1 regardless of the fact that DO concentrations never really rose as <br /> previously expected <br /> ' ASE will continue to visit the site on a weekly basis to perform the <br /> necessary O&M activities <br /> ' 6 . 0 CONCLUSIONS <br /> Monitoring wells MW-2 and MW-4, within the direct proximity of the <br /> remediation zone, have shown a one to two order of magnitude drop in <br /> hydrocarbon and oxygenate concentrations At this point in time, the <br /> ' ozone sparging operation appears to be an effective means of remediating <br /> the petroleum hydrocarbon and oxygenate compounds in the <br /> groundwater at the site On behalf of the property owner, and our client, <br /> ' we respectfully request a written authorization of the proposed <br /> remediation activities in the next 6 months This letter will be used t o <br /> gain Pre-Approval form the Underground Storage Tank Cleanup Fund of <br /> ' the costs for operation of the remediation system <br /> ' Sin h's Unocal System First six Month's Operation Report — February 2003 <br /> ' -3- <br />