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Mr. Donald Bradshaw • - 2 - • November 4, 2005 <br /> system for more complete destruction of PCE in situ, when PCE destruction will not result in the <br /> generation of unacceptable levels of chloride and TDS. Therefore, please submit a two-phased work <br /> plan for implementation of air spagring and SVE, followed by the addition of ozone. Also,please <br /> include a two-phase monitoring program to clearly document that the appropriate concentrations of PCE <br /> have been achieved for addition of ozone, and that the removal of PCE is proceeding as predicted. <br /> In addition, staff requests that the following information be included in the submittal of the two-phased <br /> work plan. First, please provide a brief description of successful ozone sparging systems that have been <br /> used at"similar" sites, and why they are considered similar. Second, in the comprehensive,two-phased <br /> monitoring plan, analysis of arsenic,hexavalent chromium, other dissolved metals, and general minerals <br /> should be included. Baseline concentrations of metals and minerals should be documented before active <br /> remediation begins. After implementation,the frequency of monitoring must ensure that addition of <br /> ozone is not adversely impacting groundwater. Ideally, ozone sparging should decrease the <br /> concentration of many metals in groundwater due to oxidation and precipitation. However, increases in <br /> arsenic and hexavalent chromium have occurred in pilot test situations. Third, please provide a <br /> contingency plan in case any of the dissolved metals increase above baseline conditions and water <br /> quality goals. Finally, please describe how LFR will evaluate what constitutes a"significant" increase in <br /> arsenic, hexavalent chromium or other dissolved metal concentrations. <br /> If you have any questions or comments, please contact Marie McCrink at 916-464-4816, or by email at <br /> mtmccrinkAwaterboards.ca.eov. <br /> �&� V_1,AqAWx( <br /> Marie McCrink, R.G., C.H. <br /> Private Sites Cleanup Unit <br /> cc: Mr.Lucas Goldstein, LFR Levine Fricke <br /> Mr. Mark Adams, Lincoln Center Environmental Remediation Trust <br /> Mr. David Gouker, City of Stockton Public Library, Margaret Troke Branch <br /> Ms. Anne Farr, Ph.D., Farr Associates <br /> Mr. David Sadoff, AIG Environmental <br /> Mr. Phil.Johnson, Sims Grupe Management <br /> Mr. Mike Infurna, San Joaquin County Environmental Health Department <br />