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Former UPRR MaintenanCL_ acility 2 22 April 2008 <br /> Tracy, San Joaquin County <br /> 2. In Section 2.0, Background, the Workplan references Appendix A for the dissolved <br /> phase total extractable petroleum hydrocarbons (TEPH) as diesel. Appendix A <br /> presents TEPH as diesel contour figures that are from the silica gel cleanup method. <br /> The Regional Water Board does not accept the silica gel cleanup method for <br /> delineating TEPH as diesel, particularly for those sites that have aged petroleum <br /> plumes. Even though the silica gel analytical method filters out what is expected to <br /> be non-hydrocarbon related compounds (polar), it also filters out diesel degradation <br /> by-products that still must be accounted for in the remedial investigation and <br /> cleanup work to be performed at the site. In the future, please do not use the silica <br /> gel cleanup method to delineate the dissolved phase TEPH as diesel at this site. <br /> As per your schedule in the Workplan, please submit the NAPL Investigation Results report to <br /> this office no later than 22 July 2008. Please notify this office at least 5 business days prior to <br /> conducting any fieldwork so that I may possibly observe sampling methods and field <br /> conditions. <br /> If you have any questions regarding this correspondence or subject matter, please contact me <br /> at (916) 464-4678 or email me at smeeks �waterboards.ca.gov. <br /> �7 <br /> te'ven W. Meeks, E. <br /> Water Resource Control Engineer <br /> CC: Mr. J. Scott Davis, P.E. Arcadis, Petaluma <br /> Mr. Michael J. Infurna, San Joaquin County Public Health, Stockton <br />