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z <br /> Groundwater Extraction and Treatment System Evaluation June 5, 1993 <br /> Sebastiani Vineyards/Woodbridge Cellars CEECON <br /> nondetectable (less than 0.5 ppb) concentrations of BTEX to 41 ppb benzene. Effluent <br /> GTS samples indicated nondetectable concentrations of TPHg during all sampling events, <br /> with the exception of 73 ppb TPHg for the sample collected on September 24, 1992, and <br /> nondetectable BTEX concentrations during all sampling events. Chain of Custody records <br /> and laboratory analyses reports are attached. <br /> DISCUSSION OF RESULTS <br /> All effluent GTS samples, with the exception of the sample collected on September 24, <br /> 1992, indicated nondetectable concentrations of TPHg and BTEX. These nondetectable <br /> concentrations of TPHg and BTEX demonstrate an almost 100 percent destruction <br /> efficiency for the currently operating GTS at the subject site. The initial effluent sample <br /> collected on September 24, 1992, indicating a TPHg concentration of 73 ppb, may be <br /> attributed to a switched sample; namely, the post spray aeration or post total aeration <br /> sample. These analytical results of the GTS samples also indicate appropriate system <br /> installation, and that the system is effectively removing and treating gasoline impacted <br /> groundwater beneath the subject site. <br /> LUAI TATIONS <br /> This report was prepared in accordance with generally accepted standards of environmental <br /> practice in California at the time this investigation was performed. This investigation was <br /> conducted solely for the purpose of presenting the results of the installation and operation <br /> of an existing groundwater extraction and treatment system at the site. No soil engineering <br /> or geotechnical references are implied or should be inferred. Evaluation of environmental <br /> conditions at the site for the purpose of this investigation is made from a limited number <br /> of observation points. Subsurface conditions may vary away from the data points available. <br /> The signatories of this document certify only those portions of the system evaluation that <br /> fall within their areas of competence. <br /> .. 5 <br />