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San Joaquin County <br /> Environmental Health Department DIRECTOR <br /> Donna Heran,REHS <br /> 600 East Main Street <br /> a �I <br /> y Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Robert McClellon, REHS <br /> y — Jeff Carruesco, REHS, RDI <br /> ov.o/ %hd Kasey Foley, REHS <br /> Website: www.s <br /> gci'Fo.Rc' 19 9 <br /> Phone: (209) 468-3420 <br /> Fax: (209)464-0138 <br /> May 21, 2010 <br /> Mr. Paul Zumberge <br /> Frontier Transportation, Incorporated <br /> 3577 West Philadelphia <br /> Chino Hills, California 91710 <br /> Subject: Frontier Transportation, Incorporated <br /> 425 Larch Road <br /> Tracy, California 95376 <br /> Dear Mr. Zumberge: <br /> The San Joaquin County Environmental Health Department (EHD) has received and reviewed <br /> Site Conceptual Model (SCM), dated March 15, 2010, prepared by your consultant, Ami Adini <br /> & Associates, Inc. (AA&A). In the SCM, AA&A proposes to submit a site-specific health risk <br /> assessment to evaluate the threat of vapor intrusion to occupants at the site, and a Corrective <br /> Action Plan (CAP), employing what AA&A defines as "Zone Remediation" to evaluate <br /> remedial alternatives. <br /> The EHD concurs that a Human Health Risk Assessment (HHRS) is necessary based on the <br /> significant concentrations of chemicals of concern detected in soil gas samples during a soil <br /> vapor study completed in January 2000. Please submit the HHRA to the EHD by September <br /> 27, 2010. Include the evaluation of Environmental Screening Levels (ESLs) established by <br /> the San Francisco Bay Regional Water Quality Control Board, California Human Health <br /> Screening Levels (CHHSLs) published by the Office of Environmental Health Hazard <br /> Assessment, California Environmental Protection Agency, and the potential for vapor intrusion <br /> into buildings. Submit a work plan to the EHD by July 30, 2010, if one is warranted to assess <br /> the potential for vapor intrusion into the existing on-site buildings. <br /> The EHD concurs that a CAP is necessary to identify a remedial technology, or a combination <br /> of technologies, capable of mitigating petroleum hydrocarbon contamination in the three <br /> zones identified by AA&A as: <br /> • Zone 1, the unsaturated and saturated soil phases in the source area containing <br /> approximately ninety percent of the contaminant mass; <br /> • Zone 2, the saturated and capillary fringe area surrounding the source zone and <br /> containing approximately ten percent of the contaminant mass; and <br /> • Zone 3, the area down-gradient of and distant from the source area. <br />