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DWI. • • <br /> ENSR International <br /> . 10411 Old Placerville Road <br /> Suite 210 <br /> 95827-2508 <br /> 04 DEC -9 PM 4: 37 Sacramento 0916)362-7100 <br /> December 7, 2004 FAX (916)362-8100 <br /> www.ensr.com <br /> Mr. James L. Barton <br /> Regional Water Quality Control Board <br /> Central Valley Region <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, CA 95670-6114 <br /> RE: Interruption in operation of Soil Vapor Extraction system at <br /> Former Unocal facility No. 5098 <br /> 5400 and 5606 Pacific Avenue, Stockton, California <br /> CAO No. 5-00-707 <br /> Dear Mr. Barton: <br /> ENSR Corporation (ENSR) has prepared this letter as you requested during a meeting with you <br /> and Mr. Brian Newman of the Regional Water Quality Control Board (RWQCB), <br /> Mr. Ben Heningburg and Mr. Mark Naugle of ENSR on December 6, 2004. This letter includes <br /> a description of recent events concerning the interruption in operation of the Soil Vapor <br /> Extraction (SVE) system and provides a detailed schedule of the steps that will be taken to <br /> restart the SVE system. <br /> ENSR is currently operating a soil and groundwater remediation system at the former Unocal <br /> facility No. 5098, 5400 and 5606 Pacific Avenue, Stockton, California. The remediation system <br /> includes air sparging (AS) and SVE. The SVE system is a 300 cubic feet per minute Baker <br /> Furnace thermal oxidizer. Between October 2003 and September 2004, operation of the SVE <br /> system was suspended, with approval of the RWQCB, because the inlet concentrations were <br /> very low. In September 2004, ENSR rehabilitated and restarted the SVE system as part of a <br /> revised system operation plan because it appeared that some lateral, down gradient migration <br /> of the petroleum hydrocarbons in groundwater had occurred. ENSR also installed additional <br /> down-gradient groundwater monitoring wells MW-28 through MW-30 to define plume limits. <br /> During a routine operations and maintenance visit on November 30, 2004, an ENSR technician <br /> discovered that the SVE system was not running. The technician identified a 4 to 6-inch <br /> diameter hole in the outside wall of the combustion chamber of the thermal oxidizer. The <br /> technician contacted Mr. Ben Heningburg. ENSR immediately scheduled a qualified service <br /> technician from Envirosupply to troubleshoot the SVE system and repair the hole by welding a <br /> metal patch onto the combustion chamber. The service technician arrived on site on <br /> December 2, 2004 prepared to patch the hole and determined that the hole could not be <br /> repaired without removing the entire combustion chamber which would require the use of a <br /> crane. On the afternoon of December 3, 2004, ENSR notified the RWQCB by electronic mail <br /> that the operation of the SVE system had been interrupted due to a failure of the insulation <br /> within the combustion chamber. <br /> \\Dcsacramento\projects\Projects\06940\5098-293\Final\Conespondence\5098120704 Ltr RWQCB.doc <br /> 35 Years of Excellence in environmental Services <br />