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GeoStrategies <br /> April 30, 1997 <br /> Mr Adadu Yemane <br /> Tosco Marketing Company <br /> 2000 Crow Canyon Place, Suite 400 <br /> San Ramon, California 94583 <br /> Subject: Fust Quarter 1997 VES Report, Unocal Station No. 6981, 4707 Pacific <br /> Avenue, Stockton, California. <br /> Mr Yemane <br /> This report summarizes the sampling and operational data for the vapor extraction system <br /> (VES) at the subject site from January through March, 1997 Location of the subject site <br /> is shown on Figure 1 The current station configuration is shown on Figure 2 <br /> . First Quarter 1997 Activities <br /> Field activities conducted at the subject site during the first quarter 1997 are discussed <br /> below GeoStrategies (GSI) Field Methods and Procedures are attached <br /> The VES effluent vapor stream was sampled by Gettler-Ryan Inc (G-R) on January 29 and <br /> February 27, 1997 The samples were analyzed for TPHg and BTEX at Sequoia <br /> Analytical in Redwood City, California (FLAP ##1210) Copies of the laboratory reports <br /> and chain-of-custody documents are attached The VES shut down on March 1, 1997, due <br /> to failure of the flame sensor, flame rod, and oxygen sensor, and remained shut down for <br /> the remainder of the quarter <br /> Between December 20, 1996 and February 27, 1997, the VES operated approximately 550 <br /> hours (23 days), or approxiinately 33% of the time The VES continued to have problems <br /> flaming out until March 1, 1997, when the system shut down due to failure of the oxygen <br /> sensor, flame sensor, and flame rod The system remained shut down through the end of <br /> the quarter Soil vapor was extracted from wells VW-2, VW-4, and VW-5 during the first <br /> quarter 1997, as field monitoring indicated these wells had the highest hydrocarbon <br /> concentrations During the first quarter 1997, the VES extracted and treated approximately <br /> 214 pounds of TPHg and 1 pound of benzene VES analytical data for the quarter are <br /> summarized in Table 1, and operational data are summarized in Table 2 <br /> 705 zaz <br /> 3164 Gold Camp Drive, Suite 240 • Rancho Cordova, CA 95670 • (916) 631-1314 . Fax (916) 631-1317 <br />