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REG 603 UPDATE-7 3/24/92 <br />• <br /> monitoring wells closest to the extraction wells) from the June <br /> sampling to the December sampling, see 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 and a <br /> reduction in the contaminant levels in the other wells will be <br /> noted. <br /> The City of Stockton POTW, has denied our "Request to Discharge <br /> Treated Groundwater From 6425 Pacific Ave. " , see Appendix A. <br /> The ground water recovery - treatment system for this site cannot <br /> be designed until the assessment of ground water treatment - vapor <br /> extraction (REMOX) has been stabilized. <br /> RECOMMENDATIONS <br /> 1. Perform ground water sampling for gasoline range <br /> hydrocarbons and fecal coliform on a quarterly bases. <br /> 2. Continue weekly air monitoring and adjustments using the <br /> 1OS50 PID-GC, until the REMOX unit is stabalized, ie. no <br /> air dilution. <br /> 3 . Provide monthly update status reports . <br /> 2 . 0 GROUND WATER <br /> 2 . 1 REGIONAL AND LOCAL GROUND WATER FLOW <br /> Ground water flow direction in 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 rhe <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 /> r L_ t tank A is a F-1 , ,rc '21 aC 1-he <br /> 5Ournwesr corner oL t' Curreii4- e.nlin paw �€ , <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 tnis site, the overall local flow direction is <br /> to the east-northeast at a relatively flat slope. Slug tests <br /> performed on the monitoring wells (May 25 , 1990) indicated <br /> hydraulic conductivities (K) , ranging from highs of 45 . 43 and <br /> 33 .48 feet/day at MW9 and MW1 respectively, to lows of 0 . 52 and <br /> PAGE 2 <br />