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kREG 603 UPDATE-9 9/14/92 <br /> 3 <br /> i <br /> i <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 and MW3 which have floating product <br /> and MW10 which was dry, 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 MW1 , MW2 , MW3 , MW10 and EX- <br /> 411 , an increase in the vacuum influence will be obtained. Also, 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 /> applied for and once approved, ground water pumping will occur <br /> from monitor wells MW1 and MW3 . 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 /> i off of by the air strapping from the tank will be processed into <br /> the thermal oxidizing unit for destruction, see Appendix D - <br /> Sewer Discharge Permit Application. <br /> As directed by San Joaquin County Health a workplan 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 to the landowners has been made and we <br /> are awaiting their requirements prior to obtaining the permission <br /> forms to place the wells on their properties . <br /> 5 . 0 RECOMMENDATIONS <br /> R <br /> { <br /> ' 1 . Perform ground water sampling for gasoline range <br /> i hydrocarbons and fecal coliform on a quarterly basis . <br /> 2 . Until the REMOX unit is stabilized, no air dilution, <br /> continue weekly adDustments and monthly monitoring , <br /> using the 1OS50 PID-GC. <br /> 3 . Provide monthly update status reports of vapor <br /> recovery/destruction. <br /> 4 . Upon receipt of the Sewer Discharge Permit, install a <br /> f ground water recovery system into MW1 and MW3 and treat <br /> the ground water by tank aeration. <br /> i <br /> PAGE 2 <br /> i <br /> I <br />