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_ tNTE f?NATIONAi <br /> E C 0 R I vL 0l,P01,A'E D 3017 Kilgore Road Suite 100 <br /> Rancho Cordova GA 95670 <br /> 916 861 0400 TEL <br /> 916 861 0430 FAx <br /> January 22, 2004 <br /> R01 E C E�W E----"D <br /> Mr Robert J Cochran JAN 2 3 2004 <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road ENVIRONMENT HEALTH <br /> P O Box 6004 PERMIT/SERVICES <br /> San Ramon, California 95843 <br /> RE Fourth Quarter 2003 Remediation Systems Status Report <br /> Chevron Service Station 9-4275 <br /> 2905 West Benjamin Holt Drive <br /> Stockton, California <br /> SECOR Project No 77CH 94275 05 0570 <br /> Dear Mr Cochran <br /> SECOR International Incorporated (SECOR) presents with this letter 1) operational data for the soil <br /> vapor extraction (SVE) and air sparge (AS) systems which are being utilized to remediate soil and <br /> groundwater beneath the subject site and 2) an evaluation of the remediation systems effectiveness <br /> during the fourth quarter of 2003 (4003) The site location map and site plan are shown as Figure 1 <br /> ® and Figure 2, respectively <br /> Operation of the SVE and AS systems was initiated at the site in April 1997 The SVE system has <br /> been disabled and the AS continues to operate A brief description and performance evaluation of <br /> the remedial system between September 17, 2003 and December 02, 2003 are presented below <br /> SOIL VAPOR EXTRACTION SYSTEM <br /> The inactive SVE system is comprised of ten SVE wells (VW-1 and GM-1 through GM-9), <br /> underground mechanical piping, a 5-horsepower (hp) positive displacement blower, and 100-cubic <br /> feet per minute (cfm) catalytic oxidizer (Figure 2) <br /> During 4003, the SVE system did not operate due to high groundwater levels The SVE system has <br /> not operated since February 1998 On December 18, 2003, depth to water in the monitoring wells at <br /> the site ranged from 1014 to 12 65 feet below ground surface (bgs) The screened intervals in the <br /> SVE wells range from 10 to 17 feet bgs, therefore water levels are currently too high for effective <br /> operation of the SVE system <br /> AIR SPARGING SYSTEM <br /> The AS system is comprised of nine AS wells (GM-1 and GM-9), underground mechanical piping, <br /> and a 1 5-hp rotary vane air compressor During 4Q03, the AS system was operational for 99% of <br /> the reporting period at an average flow rate of 14 2 standard cubic feet per minute (scfm) and an <br /> average injection pressure of 5 3 pounds per square inch gauge (psig) Routine operation and <br /> maintenance visits were conducted on October 9, November 14, and December 2, 2003 <br /> 1 1Chevron1942751Penodsc Monitoring12003 O&M14003 O&M Report 9 4275 doc <br />