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aa <br /> 19449 Riverside Drive, Suite 230, Sonoma, California 95476 <br /> CONESTOGA-ROVERS Telephone: 7079354850 Facsimile: 7079358649 <br /> & ASSOCIATES www.CRAworld.com <br /> May 22, 2008 <br /> Mr. Michael Infiuua <br /> San .ivaquin County Environmental Health Department <br /> 600 East Main Street <br /> Stockton, California 95202 <br /> Re: Groundwater Extraction and Treatment System Status - May 2008 <br /> Former Shell Service Station <br /> 2575 Country Club Boulevard <br /> Stockton, California <br /> SAP Code 136144 <br /> Incident No. 98996184 <br /> SJCEHD Case No. 1071 <br /> Dear Mr. Infurna: <br /> Conestoga-Rovers & Associates (CRA) prepared this letter on behalf of Equilon Enterprises LLC dba <br /> Shell Oil Products US (Shell) to provide San Joaquin County Environmental Health Department staff an <br /> update regarding the status of the groundwater extraction and treatment (GWE) system at this site. <br /> As previously reported, the GWE system was shutdown on March 29, 2008 when we discovered there <br /> had been an effluent discharge of tertiary butyl alcohol (TBA) to the sanitary sewer. The discharge <br /> permit conditions we have in place with the City of Stockton do not allow for the discharge of TBA or <br /> other fuel oxygenates into the sanitary sewer. We notified the City of Stockton of this effluent discharge <br /> and shut the system down while we investigated the incident to evaluate corrective measures to ensure <br /> compliance with the City of Stockton discharge permit. This is the second permit violation Shell has <br /> received for the discharge of TBA into the sanitary sewer from this GWE system. Currently the GWE <br /> system remains shutdown. <br /> The treatment system currently in place was designed and operated very conservatively recognizing the <br /> limitations of carbon treatment for TBA. The system consists of two 2,000-pound carbon vessels <br /> operated in parallel, followed by two more 2,000-pound carbon vessels in parallel, followed by two <br /> 1 ,000-pound vessels operated in series. The influent, effluent, and midfluent points were sampled <br /> weekly and analyzed for fuel oxygenates to monitor carbon usage and to assure discharge permit <br /> compliance. Any detection of TBA (or other fuel oxygenates) in the second midfluent sample (Mid-2) <br /> would trigger carbon change out for all of the carbon vessels. This plan allowed for 2,000 pounds of <br /> rcarbon after the Mid-2 sample to provide assurance that TBA would not be discharged into the sanitary <br /> sewer. Despite the conservative design and operational parameters, we were still unable to prevent TBA <br /> from being discharged into the sanitary sewer. <br /> Equal <br /> E pploymant <br /> Oppasunity Employer <br /> Worldwide Engineering, Environmental, Construction, and IT Services <br />