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Former UPRR Maintenance -cility ? 16 September 2008 <br /> Tracy, San Joaquin County <br /> previously been non-detect. In addition, the third bullet in the Conclusions and <br /> Recommendations section states that "TEPH was detected in five B-Zone and two C-Zone <br /> monitoring wells in which it had previously been generally non-detect; these wells will be <br /> sampled to confirm the presence of TEPH." We have concerns about the new <br /> occurrences of petroleum hydrocarbons in monitoring wells. Please verify when the <br /> confirmation sampling will be performed and provide the results to this office within 30 days <br /> of receipt of the laboratory data. <br /> 3. Appendix A presents TEPH as diesel using the silica gel cleanup method. As stated in our <br /> 22 April 2008 letter, the Regional Water Board does not accept the silica gel cleanup <br /> method for delineating TEPH as diesel, particularly for those sites that have weathered <br /> petroleum plumes and free product. Even though the silica gel analytical method <br /> discriminates non-hydrocarbon related polar compounds, it also removes diesel <br /> degradation by-products that still must be accounted for in the investigation and cleanup. <br /> In the future, please use EPA Method 8015M to delineate the dissolved-phase diesel at <br /> this site. <br /> If you have any questions regarding this correspondence or subject matter, please contact me <br /> at (916) 464-1588 or email me at kdominic@waterboards.ca.gov. <br /> Kathryn Dominic <br /> Engineering Geologist <br /> cc. Ms. Lisa Teague, ARCADIS, Petaluma <br /> Mr. Michael J. Infurna, San Joaquin County Public Health, Stockton <br />