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Work Plan Stewart's Beacon _ Project No.01-171.2 March 12,1990 Page: 7 Using these average values,YL=4.2.2 feet and XL;134 feet and the momentary upgradient inflow limit is 845 feet. However,it should benoted that the outer edges of the drawdown zone approach the natural water table asymptotically, and the vast peripheral parts are often of little significance for flow to the well. However,perhaps 10 percent of these distances should define a draw- down cone which has a definite effect on this remediation Thus,an effective draw-down area would have YL=42 feet,XL=13 feet and upgradient inflow rn limit of 84 feet. 3.4.2 Design of GroundWater Remediation System The extraction well will be MW1, which is approximately 20 feet deep. At present,there is about 10 feet of ground water in that aquifer. The wells will be pumped by a jet pump located in the well. They will be driven by a submersible pump located in the holding tank above ground(Figure. 8). �. The system described here was largely designed by Osterberg&Stewart,Inc.in conjunction with Geological Technics and is shown in Figure 6. From the well, the water is fed Into a large aeration tank h om its top. The top of the tank is painted black formaximum heat absorption.from solar radiation. The treatment starts by introducing microbubbles into a stream of water. In essence, the jet pump forms an air stripping which causes a mass transfer of volatile hydrocarbons from the liquid phase to the gas phase. A vapor stack releases the emission into the atmosphere. If large amounts of contamination are extracted, they will separate as a second liquid phase In the tank and can be removed and recycled. However,this is not expected in this case. After aeration,the water is piped from the bottom of the tank. 13y this stage of the process, the water is generally well within standards to be released into city sewage or storm drain systems. However,to safeguard against possible "'J' extreme situations or malfunctions, the water will finally be passed through two activated carbon canisters (Westates Aqua Scrub ASC-200) before being released. Sampling ports are supplied at the well exit,after the aeration tank and after the first and second carbon canisters. 3.4.3 Field Testing of System Several aspects of the system must be tested careftilly in order to ensure proper function. The most significant aspect of testing is the proper.draw-down.and—_.--_. --- - -water capture by the wells. A pump#est will be performed in the initial phase of the interim ground water remediation. This field testing is necessary because - a1 NMI,111MR-Ma a M."111111