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REG 603 UPDATE-8 7/17/92 <br /> • <br /> approximately 1473 hours after commencement of vapor extraction <br /> compared to the ground water sample results obtained on March 10, <br /> 1992, 3480 hours after commencement of vapor extraction, show a <br /> decline in the extent of the the dissolved constituents in all of <br /> the monitoring wells with the exception of MW1, MW3 and MW10 which <br /> have floating product, 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 /> 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 need for ground water recovery-treatment cannot be made, until <br /> the assessment of ground water treatment by vapor extraction has <br /> been completed for this site (REMOX unit has been stabilized with <br /> no air dilute) . <br /> 5.0 RECOMMENDATIONS <br /> 1 Perform ground water sampling for gasoline range <br /> . hydrocarbons and fecal colLform 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 /> 2 0 GROUND WATER <br /> 2.1 REGIONAL AND LOCAL GROUND WATER FLOW <br /> Ground water flow direction Ln this region is to the west - and <br /> towards south Stockton from the foothills of the Sierra Nevada <br /> Mountain Ranges, and towards the east from the Sacramento-San <br /> Joaquin Delta. At present, encroachment of saline waters from the <br /> Delta is impairing the quality of the ground water in the Stockton <br /> area <br /> WEGE surveyed each well (top of casing) with a transit using the <br /> southwest corner of the current tank pad (see Figure 3) as the <br /> datum. Survey readings were recalculated to correct elevations to <br /> the USGS topographic map (USGS East Stockton Quad , Figure 2) . <br /> Based upon ground water elevation measurements obtained thoughout <br /> the evaluation of this site, the overall local flow direction as <br /> . to the east-northeast at a relatively flat slope Slug tests <br /> PAGE 2 <br /> I <br />