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R603 UPDATE-10 11/09/92 <br /> Ground water elevation measurements show that the ground water is <br /> being mounded at the lower K value wells MW3 and MW10 , while the <br /> overall flow direction is to the northeast and southeast. <br /> Ground water sample results obtained on December 17 , 1991, <br /> approximately 1473 hours after commencement of vapor extraction, <br /> compared to the ground water sample results obtained on June 18 , <br /> 1992, 5885 hours after commencement of vapor extraction, show a <br /> decline in the extent of the dissolved constituents in all of the <br /> monitoring wells except MW1, MW3 and MW10 . These wells have <br /> floating product, see Table 1 and Figure 5 . <br /> It is felt that once the air dilute has been completely closed and <br /> all vacuum recovery can be directed to MW1, MW2, MW3 , MW10 and EX- <br /> 4" , 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. Once the ground water recovery - treatment system has <br /> . been completed, pumping will occur from monitor wells MW1 and MW3 . <br /> Treatment will be tank stripping, utilizing the "Convault" as a <br /> 1000 gallon tank stripper to batch treat approximately 300 gallons <br /> every 5 hours. All vapors driven off of by the air stripping from <br /> the tank will be processed into the thermal oxidizing unit for <br /> destruction, see Appendix D -water Discharge Permit. <br /> As directed by San Joaquin County Health, a work plan has been <br /> developed to place two down gradient monitoring wells east and <br /> northeast of MW8 to define the lateral extent of the ground water <br /> plume. Initial contact with the landowners has been made and we <br /> are awaiting their requirements before obtaining the permission <br /> forms to place the wells on their properties. <br /> 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 - adjustments and monthly monitoring <br /> using the lOS50 PID-GC. <br /> 3 . Provide monthly update status reports of vapor <br /> recovery/destruction. <br /> i4. Upon receipt of the Sewer Discharge Permit, install a <br /> ground water recovery system into MW1 and MW3 and treat <br /> PAGE 2 <br />