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R603 UPDATE-10 11/09/92 <br /> compared to the ground water sample results obtained on September <br /> 22 , 1992, 7486 hours after commencement of vapor extraction, show <br /> a decline in the extent of the dissolved constituents in all of <br /> the monitoring wells except MW3 and MW10 . These wells have <br /> floating product, and MW12 which was sampled for the first time on <br /> September 22, 1992, see Table 1 and Figures 5A and 5B. <br /> It is felt that once the air dilute has been completely closed and <br /> all vacuum recovery can be directed to MWl, MW2, MW3 , MW10 and EX- <br /> 411 , an increase in the vacuum influence will be obtained and a <br /> more substantial reduction in the contaminants, found in the other <br /> wells, will be noted. <br /> The permit to dump treated ground water to the sewer has been <br /> received and once the ground water recovery - treatment system has <br /> been completed, pumping will occur from monitor wells MW1 and MW3. <br /> Non certified results show that pulling fresh air across the fluid <br /> air .interface within the ConVault (tank) strips the hydrocarbons <br /> from the water that are presently stored in the tank. The <br /> increased active air spargeing that will occur in the tank should <br /> greatly reduce contaminant levels of the water that will be pumped <br /> . from MW1 and MW3 for treatment. Treatment will be tank stripping, <br /> utilizing the "ConVault" as a 1000 gallon tank strapper to batch <br /> treat approximately 300 gallons every 5 hours. All vapors driven <br /> off by the air strapping from the tank will be processed into the <br /> thermal oxidizing unit for destruction, see Appendix D -Water <br /> Discharge Permit. <br /> The activities described in the work plan, to place and sample two <br /> offsite ground water monitoring wells, have been completed, see <br /> Appendix C. <br /> 5.0 RECOMMENDATIONS <br /> 1 . Perform ground water sampling for gasoline range <br /> hydrocarbons and fecal coliform on a quarterly basis. <br /> 2 . Until the REMOX unit is stabilized, no air dilution, <br /> continue weekly ad3ustments and monthly monitoring <br /> usinar the 10550 PTD-GC. <br /> 3 . Provide monthly update status reports of vapor <br /> recovery/destruction. <br /> 4 . once the ctap^r ir-oe^fycroy r system has stabilized, install a <br /> ground water recovery system into MWI and MW3 and treat <br /> the ground water by tank aeration - vapor destruction <br /> . using the REMOX incinerator. <br /> PAGE 10 <br />