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Art <br /> 'Your request to alter the sampling requirements for the five monitoring wells on site cannot be <br /> approved until the following procedure is completed. All of the monitoring wells should be <br /> sampled at the next quarterly event by EPA Methods 8015 modified for Total Petroleum <br /> Hydrocarbons as Gasoline (TPH-G) and EPA Method 8020 for Benzene, Toluene, Ethyibenzene, <br /> and Xylene (BTEX). In addition, please report in the 8020, any detection of MTBE (Methyl <br /> Tertiary Butyl Ether)just before the benzene spike. If present, PHD-EHD recommends a <br /> confirming analysis by EPA Method 8260 to rule out any false positives that the 8020 may have <br /> produced. <br /> Once the presence of MTBE is investigated, PHS_EHD will evaluate the sampling frequency <br /> requirements. <br /> Please continue to investigate remedial,alternatives and possible explanations for the continuing <br /> high levels of groundwater contamination. Groundwater treatment technologies are changing and <br /> evolving constantly and inexpensive methods are surfacing in the literature monthly. With such <br /> high levels of contaminates in the groundwater below your site (TPH-G at 53,000 ppb and <br /> Benzene at 10,100 ppb in MW-1), you currently do not meet minimum standards for monitoring <br /> only or remediation by natural attenuation; and you will be required to perform active <br /> .remediation in order to lower the contaminant levels. <br /> I hope that I have responded to your concerns in a timely manner as you have requested and I am <br /> ,very interested in your plans for this site. Please contact me at (209) 468-3454 should you wish <br /> to discuss these matters or schedule an appointment. <br /> Donna Heran, REHS, Director <br /> 'Environmental Health Division <br /> !Michael Infurna, Senior REHS Mar�tLagorioo, �HS <br /> Site Mitigation Unit-LOP Lead Senior <br /> MI <br /> c: Wm. J. Hunter& Associates - Sacramento, CA. 95825 <br />