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Victor Shell,Lodi <br /> Page 2 <br /> The extent of the methyl tert-butyl ether (MTBE) contamination in groundwater has not <br /> been defined. Although the reported groundwater flow direction fluctuates, the highest <br /> concentration of the MTBE contamination has been consistently detected in MW-1 and <br /> MW-3. EHD directs the next investigation of the plume be in directions beyond MW-1 and <br /> MW-3. Submit a work plan that will define the extent of the groundwater contamination by <br /> June 5,2002. <br /> The concentrations of MTBE in the groundwater samples have been consistently over <br /> 10,000 µg/1(or parts per billion,ppb). According to Step 3 within the State Water <br /> Resources Control Board (SWRCB) Guidelines for Investigation and Cleanup of MTBE and <br /> other Oxygenates final draft dated 30 Match 2000, sites with persistent concentrations of <br /> MTBE over 10,000 ppb should perform interim remediation to reduce the concentrations <br /> and mass before the plume can spread. <br /> According to the SWRCB Guidelines geologic data should be gathered and used to estimate <br /> the approximate travel time for the contaminant plume to reach nearby receptors. If the <br /> contaminant travel time to the nearest receptor is estimated to be less than 5 years, then a <br /> remedial action plan should be implemented in less than a year. <br /> Submit an interim remediation work plan that will reduce the MTBE/oxygenate mass and <br /> hydraulically control the spread of the MTBE/oxygenate plume to EHD by June 22, 2002. <br /> If you have any questions,please feel free to contact Jeffrey Wong at (209) 468-0335. <br /> Donna Heran,REHS,Director <br /> Environmental Health Department <br /> Jeffrey Wong, Senior REHS Margaret agorio,REHS <br /> LOP/Site Mitigation Unit IV Supervisor <br /> C: CRWQCB, Central Valley Region—Marty Hartzell <br /> C: Cambria Environmental Technologies,Inc. -Joe Neely <br />