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product and also dewater the area beneath and downgradient of the former tank field, allowing the vapor extraction system to effect a cleanup in that area. The cone of depression and the ' associated radius of influence generated by the groundwater pumping system will be closely monitored and controlled to ensure that the upgradient source of hydrocarbons is not pulled onto the site The pump test determined that a pumping rate of 3 gpm each from wells RW 1, RW2, ' and RW3 will be required to achieve the desired drawdown. In sizing the system for treatment, it is estimated that recovery well RW4 and V 1 will also produce water at 3 gpm, and a buffer capacity of 5 gpm has been added in case any farther-downgradient wells are required, for a total system capacity of 20 gpm A suitable pump system (electrical or pneumatic) will be selected to extract groundwater 2,5.2 Groundwater Treatment System Design The groundwater treatment system has been designed to treat a waste stream containing petrole- um hydrocarbons in the gasoline boiling point range The system is designed to process a ' maximum of 20 gpm. The effluent from the treatment system is expected to have no detectable concentrations of TPH and BTEX, Method 8240 compounds, Method 8270 compounds, or prior- ity pollutant metals The major components of the groundwater treatment system are an ultraviolet (UV) sterilizer, an oil/water separator, an LPH storage tank, a holding tank to accumulate recovered water, the air stripper, a second holding tank to accumulate stripped water, two activated carbon vessels plumbed in series, and a final holding tank in which the headspace vapor concentration will be monitored A piping and instrumentation diagram of the system (Figure 9) is included in a pocket at the end of the report, along with a flow diagram showing flow rates and concentrations throughout the system (Figure 10) ' The recovered groundwater will initially be passed through ultraviolet light sterilizer UV1. The sterilizer will be used to kill bacteria in the groundwater to eliminate bacterial growth throughout ' the treatment system The unit selected is rated to sterilize waste water at a rate of 20 gpm ' From the sterilizer the groundwater flows into oil/water separator T1 Here any LPH is separated and flows by gravity to temporary product storage tank T2 An oil/water separator with a maximum flow rate of 20 gpm has been selected ' Water containing hydrocarbons drocarbons flows from the oil/water separator into holding tank Y T3 A constant level is maintained in tank T3 by means of the recirculation system placed ' between the air stripper and holding tank T4 A check valve in the recirculation line leading back to tank T3 prevents water from bypassing the air stripper. This recirculation system allows for a continuous flow of water through the air stripper. A continuous flow of water must be ' �6Ww2W394Zriu19lAx 15