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� r i . 12 July 2001 AGE-NC Project No 98-04432 Page 6of10 and U S Environmental Protection Agency, 1985) Prior to mobilization, all underground trenching areas will be clearly marked and a utility clearance obtained through Underground Service Alert 3 2 GROUND WATER PUMP AND TREAT SYSTEM Based on the MTBE-impact encountered in the MBP site ground water monitoring wells and grab water samples collected during the ground water aquifer pumping test, well EW-1 appears to be located in the area of highest known ground water MTBE contamination at the site Therefore, AGE proposes to install a four-inch diameter dedicated Grundfos submersible pump (model 5E5) inside the six-inch diameter extraction well EW-1 The Grundfos pump will be designed to operate continuously at a low flow rate ranging between four and five gallons per minute (GPM) Utilizing the above referenced Grundfos submersible pump, ground water will be extracted from the six-inch diameter extraction well,routed through underground PVC piping to an on-site 750-gallon above ground storage poly tank (holding tank) From the holding tank, ground water will be processed through a two-stage treatment system The two stages of the pump and treat system will utilize two 2,000-pound canisters of granular activated carbon(GAC) to address MTBE A schematic diagram of the GAC ground water treatment system is depicted in Figure 3, additional information is in Appendix B Treated water will be discharged into the City of Manteca sanitary sewer system located within Cowell Avenue AGE proposes to operate the pump-and-treat interim remediation system within the upper water table AGE proposes to install dedicated Levelogger pressure transducers (model L) in the six-inch diameter ground water extraction well and in selected ground water monitoring wells during the first month of interim remediation to monitor the influence of the draw-down at the site Data obtained from the transducers will be useful for monitoring and maximizing the capture zone of the extraction well 33 WELL AND PROCESS PUMP CONTROLLERS Both the extraction well pump and the water treatment process pump will be controlled by PumpTec controller,the ground water extraction pump will operate on and independent controller The pump control will be supplied by an amperage sensing/time control switch This switch will detect a decrease of amperage when water level drops below the impeller intake from the,Grundfos pump • The process pump, located after the holding tank, will be controlled by 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-inch below the emergency shut-off switch and activate the process pump Intermediate pump-off switches will be utilized near the bottom of the holding tank to turn the process pump off Advanced CeoEnvfronmental,Inc