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Mr. Ed Ralston 1 -2 - 13 August 2008 <br /> Former Union Oil Bulk Plant, Tracy . <br /> 2. It is unclear how ConocoPhillips plans to reduce soil concentrations that exceed the <br /> gross contamination screening levels. By 6 October 2008, ConocoPhillips needs to <br /> submit a plan for addressing how it plans to reduce the concentrations and the potential <br /> human health risks associated with contact with these soils. <br /> 3. Soil concentrations between five and eight feet bgs exceed the ESLs, and the current <br /> property owner plans to develop the Site for commercial use. Regional Water Board staff <br /> are concerned about the potential vapor intrusion at the Site, particularly into future <br /> buildings. By 6 October 2008, ConocoPhillips needs to submit a work plan to collect soil <br /> vapor samples. The work plan should follow the Department of Toxics Substances <br /> Control 15 December 2004 Guidance for the Evaluation and Mitigation of Subsurface <br /> Vapor Intrusion to Indoor Air. <br /> In summary, by 6 October 2008 please submit the results of the leachability modeling, <br /> information on how ConocoPhillips plans to address the soil concentrations, and a work plan to <br /> collect soil vapor samples. <br /> If you have any questions, you may contact me by phone at (916) 464-4819 or by email at <br /> ksheltonawaterboards.ca.gov. <br /> KRISTI SHELTON <br /> Water Resources Control Engineer <br /> Aboveground Tanks Cleanup Unit <br /> cc: Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, Stockton <br /> Mr. Mark Bare, Stantec Consulting Corp., Rancho Cordova <br />