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ry <br /> V�r <br /> N_ SECOR <br /> �� NR 7 Kilgore Road Suite 500 <br /> ® R INCORPORATED Rancho Cordova <br /> CA 95670 <br /> 1U1µ 916 861 0400 7eL <br /> 916 861 0430 FAX <br /> October 31, 2003 EN�1R�� SERVICES <br /> PERM <br /> Mr Robert J Cochran <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road <br /> P O Box 6004 <br /> San Ramon, California 95843 <br /> RE Third 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 third quarter of 2003 (3Q03) 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 June 6, 2003 and September 16, 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 3Q03, the SVE system did not operate due to high groundwater levels The SVE system has <br /> not operated since February 1998 Depth to water in the monitoring wells at the site ranged from <br /> 10 60 to 12 82 feet below ground surface (bgs) on September 24, 2003 The screened intervals in <br /> the SVE wells range from 10 to 13 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 3Q03, the AS system was operational for 70% of <br /> the reporting period at an average flow rate of 16 standard cubic feet per minute (scfm) and an <br /> average injection pressure of 5 8 pounds per square inch gauge (psig) Routine operation and <br /> • maintenance visits were conducted on July 14, August 20, and September 16, 2003 <br /> 1 IChevron1942751Periodic Monitoring12003 O&M13003 O&M Report 9 4275 doc <br />