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' 20 June 2005 AGE-NC Project No 05-1306 ' Page 7 of S t4 3 1 Ground Water Extraction System A submersible water pump with an automatic float switch will be utilized to dewater the excavation To minimize sediment intake through the pump, the bottom of the pump/motor assembly will be suspended approximately one foot from the bottom of the excavation Ground water will be continuously pumped from the excavation at a rate of approximately 15 GPM to a 1,000-gallon holding tank and piped to the ground water treatment system via a water-tight surface hose 4 3 2 Ground Water Treatment System The extracted ground water will be routed to a 1,000-gallon holding tank, from which it will pass ' through a process pump and a 1-micron sediment bag filter to the single-stage treatment system The holding tank is equipped with various level control switches which serve to control the rate at which extracted water is introduced into the treatment vessels,to provide safety shutoff capabilities and to ' allow coarser sediment to settle out prior to treatment The process pump, located directly behind the holding tank,passes extracted ground water from the holding tank to the treatment system The pump will be controlled by a PumpTec (or equivalent) controller, as well as additional electrode switches placed at various levels in the holding tank An ' emergency shut-off switch will be located immediately below the top of the holding tank, an intermediate pump-on switch will be placed approximately 8-inches below the emergency shut-off switch and activate the process pump, and intermediate pump-off switches will be utilized near the ' bottom of the holding tank to turn the process pump off The treatment stage consists of passing hydrocarbon-impacted ground water through a 2,000-pound ' granular Activated Carbon (GAC) adsorption vessels, the vessels are designed to adsorb TPH-g, TPH-d and BTEX compounds Sample ports will be located at the influent and effluent ends of each vessel to allow detection of potential media break through and to obtain final discharge samples The ' system layout is depicted in Figure 5 Electricity is readily available to the site Either a dedicated,Pacific Gas&Electric(PG&E)-installed ' electrical meter or a gasoline-powered electric generator will be connected directly to the ground water extraction system to provide power 4 3 3 Ground Water Treatment Monitoring and Maintenance Activities During ground water treatment, ground water influent and effluent of the treatment system, and �. operational parameters (ground water flow meters, fluid level sensors, total flow indicators)will be ' Advanced GeoEnvironmental,lac 1