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SECOR www sec or com <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> S E C 4 R INCORPORATED Rancho Cordova,CA 95670 <br /> 916 861 0400 TEL <br /> 916 861 0430 Fax <br /> July 29, 2003 ; <br /> Mr Robert J Cochran <br /> Chevron Environmental Management Company LNVIRONNI 17 I­"`ALTS" <br /> 6001 Bollinger Canyon Road PERNIMSERVUS <br /> P O Box 6004 <br /> San Ramon, California 95843 <br /> RE Second 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 second quarter of 2003 (2003) The site location map and site plan are shown as Figure <br /> 1 and Figure 2 <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 March 18, 2003 and June 17, 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 2003, 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 /> 6 84 to 12 30 feet below ground surface (bgs) on March 18, 2003 The screened intervals in the <br /> 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 2003, the AS system was operational for 88% of <br /> the reporting period at an average flow rate of 11 2 standard cubic feet per minute (scfm) and an <br /> average injection pressure of 7 1 pounds per square inch gauge (psig) Routine operation and <br /> maintenance visits were conducted on April 24, May 2, May 21, June 2, and June 6, 2003 System <br /> down time is suspected to be caused by a power failure <br /> I IChevron1942751Periodic Monitoring12003 O&M=03 O&M Report 9-4275 doc <br />