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1 <br /> ' Mr Ron Rowe <br /> Page 4 <br /> The VES was shut down on January 18 due to a broken ignitor and heat transfer system casting <br /> ' New components were installed and the system was restarted and placed back in full time operation <br /> on February 23, 1999 The system functioned properly during the month of March <br /> ' During the first quarter 1999, the VES was monitored on a weekly basis (except during system <br /> shutdown) The systems monitoring data sheets are included in Attachment C On January 18, and <br /> ' March 22, 1999 influent and effluent vapor samples were collected Additional influent and <br /> effluent samples were collected on March 29, 1999 and submitted to Sequoia Analytical for <br /> analysis due to the loss of the effluent sample through a leak in the tedlar sample bag after the <br /> ' March 22, 1999 sampling event The samples were analyzed for total purgeable petroleum <br /> hydrocarbons (TPPH) and BTEX <br /> ' Vapor Sample Analytical Results <br /> Laboratory reports are included in Attachment D and are summarized in Table 4 Based on the <br /> TPPH concentrations, the destruction efficiency of the thermal oxidizer during the January and <br /> ' March sampling rounds was 93% or better No samples were collected in February due to system <br /> malfunction Therefore, no effluent emerged from the system and destruction efficiency could be <br /> calculated <br /> Overall, analytical results of first quarter 1999 influent samples indicated vapor concentrations have <br /> not declined significantly from the fourth quarter 1998 <br /> System Evaluation <br /> ' The VES has been removing hydrocarbons from subsurface soil since November 19, 1997 at flow <br /> rates ranging from 270 to 380 cubic feet per minute including dilution air <br /> ' As of March 31, 1999 the system had been in operation for 7,010 hours Based on graphical <br /> interpolation between measured influent vapor concentrations, as of March 31 an estimated 11,450 <br /> pounds of hydrocarbon contamination had been removed from the soil Table 5 summarizes flow <br /> ' and vapor concentration averages as well as the total hydrocarbon mass removed from the soil <br /> ' RECOMMENDATIONS <br /> Develop Case Closure Criteria and Schedule <br /> ' In view of the relative success of the soil remediation effort and the static groundwater plume <br /> condition we recommend that site-specific criteria and a tentative schedule for closure be developed <br /> ' for this case <br /> -klgmrl l qm 1999 <br /> I <br />