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R603 UPDATE-11 11/19/92 <br /> T <br /> 4. Once the vapor recovery system has stabilized, install a <br /> ground water recovery system into MW1 and MW3 and treat <br /> the ground water by tank aeration - vapor destruction <br /> using the REMOX incinerator. <br /> 2 .0 GROUND WATER <br /> 2. 1 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 the <br /> Delta is impairing the quality of the ground water in the Stockton <br /> area. <br /> Based upon ground water elevation measurements obtained throughout <br /> the evaluation of this 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 /> 1. 99 feet/day at monitoring wells MW2 and MW10 respectively. <br /> These drastically different K values (in the above mentioned <br /> wells) along with the monthly depth to ground water measurements <br /> help determine if the ground water beneath the site is in a <br /> recharge or discharge cycle. If the ground water surface shows <br /> flow occurring from MW1 towards MW2, a recharge cycle is <br /> occurring. If the ground water surface shows flow occurring from <br /> MW2 towards MW1, a discharge cycle is occurring. Measurements <br /> obtained on OCTOBER 8 , 1992, (Figure 4A) , show a continued decline <br /> in ground water elevations. The flow direction is towards MW1 and <br /> mhe newly installed well MW12 . The flow towards MW1 can be <br /> attributed to vapor extraction removing moisture from the vadose <br /> zone and capillary fringe with water replacement being provided by <br /> the water table. This lowering of the ground water at MW1 is <br /> localized at the vapor recovery wells MW1, MW2, MW3 and MW10 . The <br /> flow gradient towards MW12 can be considered the normal gradient <br /> near this site. This figure represents a continuation of the <br /> discharge cycle that was initiated in February, 1992 . <br /> Figure 4B, represents the gradient beneath the site from ground <br /> Ater measurements obtained NoveTaber 111 1992 . This figure is <br /> very similar to the October, 1992 measurements but show minor <br /> recharge in ground water elevations. The dewatering valley <br /> . created by vapor extraction at MW1, MW2, MW3 and MW10 is more <br /> pronounced and indicates a larger are of influence from vapor <br /> PAGE 3 <br />