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L � <br /> Mr Lynn Walker, Shell Oil Company DRo <br /> February 23,1995 ( 9347-3011) <br /> Groundwater Pumping With Dischame to Sanitary Sewer <br /> The groundwater recovery system operation (pumping from wells RW-I and RW-2) commenced <br /> on March 2, 1993 Quarterly sewer discharge sampling and reporting has been performed <br /> according to the discharge permit issued by the City of Stockton Municipal Utilities Department <br /> Sewer discharge results since system startup in March 1993 and a copy of the most recent <br /> quarterly sewer discharge report are included as Attachment 3 Pumping from RW-1 was shut <br /> down on September 20, 1994, as the groundwater samples from the well did not contain any <br /> detectable hydrocarbons during the previous quarterly sampling event (August 16, 1994) During <br /> the period between March 2, 1993 and December 17, 1994, an estimated 5,146,932 gallons of <br /> groundwater containing dissolved hydrocarbons were pumped from RW-1 and RW-2 and <br /> discharged into the sewer Total Petroleum Hydrocarbon concentrations ranged from less than <br /> 0 05 to 1 5 parts per million (ppm), benzene concentrations ranged from less than 0 0005 to 0 026 <br /> ppm System monitoring information, including pumping rates, hydrocarbon concentrations, and <br /> discharge to the sanitary sewer, is included in Attachment 3 <br /> Groundwater Oxygenation System <br /> Operation of the GO system commenced on July 11, 1994 with air diffusers in operation in wells <br /> MW-1, MW-2, and MW-3 Air diffusers in wells RW-1, and RW-2 were activated on November <br /> 16, 1994 GO system operation was shut down (November 29, 1994 - January 6, 1995) due to <br /> repair of the system's electric control panel Results of GO system monitoring for dissolved <br /> oxygen are presented as Attachment 4 Attachment 4 includes weekly dissolved oxygen <br /> monitoring for one month after activation of air diffusers in RW-1, and RW-2 as required by the <br /> San Joaquin County Environmental Health Division <br /> Remediation system operation and monitoring will be continued per regulatory requirements The <br /> interpretations and conclusions contained within the attachments represent our professional <br /> opinions These opinions are based on currently available information and were developed in <br /> accordance with currently accepted geologic,hydrogeologic, and engineering practices at this time <br /> and for this specific site Other than this, no warranty is implied or intended <br /> 93473011 EQR 2 , <br />