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Third Quarter 2002 Monitoring,Sampling,and Remediation Progress Report 6 <br /> 7-Eleven,Inc,Store#19976, 1399 North Main Street Manteca,CA October 31, 2002 <br /> Remediation Progress <br /> On August 1 and 22, 2002, SVE was conducted using the horizontal vent wells for a period of 6 and 3 <br /> 1 hours, respectively On August 1, extracted vapor levels ranged up to 4,500 ppm[v] and declined to 1,500 <br /> ppm[v] by the end of the event On August 22, extracted vapor levels ranged up to 2,000 ppm[v]and <br /> declined to 100 ppm[v] by the end of the SVE event It appears at this time SVE has reduced soil vapor <br /> ' levels of hydrocarbons and oxygenates in the source area (the UST pit) Remediation was not conducted <br /> in July as permanent power was not yet available at the site (installation completed late July 2002), <br /> remediation was not conducted by September as the Permit to Operate had not yet been obtained for the <br /> equipment designated (currently)for use at the site (a 250-cfm thermal oxidizer) The original permit was <br /> for a 150-cfm King Buck unit, for which the larger unit has been substituted <br /> Periodic mobile treatment events conducted throughout 2002 may be successfully reducing dissolved <br /> MTBE levels in source area well MW-2 Other wells previously demonstrating concentrations of more <br /> ' than 100 pg1L MTBE (MW-1, MW-5) have also declined since the second quarter 2002 and/or earlier <br /> sampling events or are remaining stable in concentration As of the third quarter 2002, dissolved MTBE <br /> ' levels at the site ranged between non-detectable and 1,800 pg/L, with only well MW-2 containing more <br /> than 1,000 pg/L <br /> Conclusions and Recommendations <br /> Since a dedicated electrical power source has been installed at the site, remediation is scheduled to occur <br /> ' every two weeks once the Permit to Operate is obtained SVE is effective in reducing MTBE/hydrocarbon <br /> concentrations in the vadose zone of the source area, which appears to be beneficially impacting <br /> dissolved plume concentrations Air and/or oxygen sparging will be added to the remediation process <br /> ' during the fourth quarter 2002 to further reduce saturated-zone concentrations <br /> 1 <br /> 19976=DOC <br /> 1 <br />