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rate of approximately 0.5 gallons per minute (gpm). This flow rate should induce a capture zone <br /> sufficient to provide adequate hydraulic controls and expose targeted contaminated soil in this area. <br /> Extracted fluids will be pumped into an above ground oil/water separator, where the water will be <br /> transferred into the groundwater treatment system. The groundwater treatment system will consist <br /> of three 200 pound vessels of activated granulated carbon in series. A sampling port and flow meter <br /> will be installed in line prior to system discharge. Water will be discharged into the storm drain <br /> under an NPDES permit. NPDES permit applications will be submitted subsequent to PHS/EHD <br /> approval of this letter supplement and the September 8, 1997 Work plan for Corrective Action. <br /> System Operation <br /> Operation and maintenance of the system will require regular site visits to monitor system <br /> performance, adjust valves, collect vapor samples, and perform normal system maintenance in <br /> compliance with air and water discharge requirements. Groundwater will be sampled on a quarterly <br /> basis and the groundwater gradient will be measured at each sampling event. Quarterly monitoring <br /> reports will be submitted to PHS/EHD as required. It is expected that mitigation of the site will <br /> require at least 3 years of system operation. After one year of operation, the performance of the <br /> system will be evaluated to determine if any wells need to be added to the air or groundwater <br /> collection systems, or if additional system modifications are necessary. <br /> If you have any questions, please contact the undersigned at (562) 921-3581. <br /> Written by: Reviewed by: <br /> Ray and C. Friedrichsen !BreW4�e�r, RG, CHG <br /> Project Manager Hydrogeologist <br /> Environmental Geologist <br />