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1 <br /> 6ETTLER - RyApi <br /> INc. <br /> • <br /> January 22, 1998 <br /> Mr Ed Ralston <br /> Tosco Marketing Company <br /> Environmental Compliance Department <br /> 2000 Crow Canyon Place, Suite 400 <br /> San Ramon, California 94583 <br /> Subject: Fourth Quarter 1997 VES Report, Unocal Station No. 6981, 4707 <br /> Pacific Avenue, Stockton, California. <br /> Mr Ralston <br /> This report summarizes the sampling and operational data for the vapor extraction system <br /> (VES) at the subject site from October through December, 1997 Location of the subject <br /> site is shown on Figure 1 The current station configuration is shown on Figure 2 <br /> Fourth Quarter 1997 Activities <br /> Field activities conducted at the subject site during the fourth quarter 1997 are discussed <br /> below Gettler-Ryan Inc (GR) Field Methods and Procedures are attached <br /> Due to problems later diagnosed as a failed flame detector (fire eye), the VES only <br /> operated sporadically between September 28 and October 26, 1997, when it was shut off <br /> GR contracted with the VES' manufacturer to replace the failed detector on December 5, <br /> 1997 During these repairs, the VES was briefly restarted (approximately 3 hours) to <br /> confirm operation of the flame detector Influent and effluent samples were also collected <br /> at this time to confirm destruction efficiency, then the VES was shut down pending receipt <br /> of analytical data GR returned to the site on December 21, 1997, to replace the dilution <br /> valve motor control and to restart the VES GR collected influent and effluent vapor <br /> stream samples on December 29, 1997 The samples collected during both December <br /> sampling events were analyzed for TPHg and BTEX at Sequoia Analytical in Redwood <br /> City, California (ELAP #1210) Copies of the laboratory reports and chain-of-custody <br /> documents are attached <br /> Between December 21 and December 29, 1997, the VES operated approximately 224 hours <br /> (9 3 days), or 100% of the time Soil vapor was extracted from wells VW-2, VW-4, and <br /> VW-5 during the fourth quarter 1997, as field monitoring indicated these wells had the <br /> 785520-4 <br /> r <br /> 6747 Sierra Court , Suite J Dublin , California 94568 (51 0) 551 -7555 <br />