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• • <br /> Frontier Transportation Page 2 <br /> 425 Larch Road August 5, 2011 <br /> Tracy, California 95376 <br /> express concerns regarding the pending remediation at this site. If none is received, fieldwork <br /> may commence on 15 August 2011. Submit a Well and Boring Permit Application and <br /> installation/inspection fees to the EHD for the installation of the 11 DPE wells and complete <br /> well installations by 21 September 2011. Please note that the EHD's hourly rate has <br /> increased from $122 per hour to $125 per hour for issuing permits and inspections. <br /> The EHD also reviewed Soil Gas Sampling and Human Health Risk Assessment Report <br /> (report), dated 12 April 2011, prepared by AA&A. In the report, AA&A presented the analytical <br /> results from soil gas samples SV1 through SV3 and SV1-Dup. Concentrations detected in soil <br /> gas samples SV1 and SV1-Dup exceeded the soil vapor Tier 1 Environmental Screening <br /> Levels for TPH-g, benzene, ethylbenzene, and MTBE established by the California Regional <br /> Water Quality Control Board, San Francisco Bay Region. Using the soil gas results from SV1, <br /> AA&A completed a human health risk assessment (HHRA) using the Johnson and Ettinger <br /> model to calculate indoor air concentrations and resulting cancer risk and noncancerous <br /> hazard. Results from the calculated noncancerous hazard index (1.7) exceeded the target <br /> hazard quotient of 1.0, and the calculated cancer risk (5E-04) exceeds the carcinogenic risk of <br /> 10E-06. Based on these results, AA&A concluded that remediation is necessary to prevent or <br /> reduce harmful human health effects from vapor intrusion of hazardous chemicals. By letter <br /> dated 04 February 2011, the EHD had directed an evaluation of the fluctuations in MTBE <br /> concentrations prior to determining whether corrective action is necessary at this site; <br /> however, based on results from the HHRH, the EHD is of the opinion that corrective action <br /> should be implemented prior to evaluating the fluctuations in MTBE concentrations. <br /> If you have any questions, please contact Vicki McCartney at (209) 468-9852, or by e-mail at <br /> vmccartney@sjcehd.com. <br /> Sincerely, <br /> Victoria L. McCartney, REHS� Nuel C. Henderson, Jr., PG <br /> Senior Registered Environmental Healt Specialist Engineering Geologist <br /> c: Ms. Gabriele Baader, PG, Ami Adini & Associates, Inc., 4130 Cahuenga Blvd., Suite 113, <br /> Los Angeles, California 91602 <br /> Mr. James L.L. Barton, PG, California Regional Water Quality Control Board Central <br /> Valley Region, 11020 Sun Center Drive, Suite 200, Rancho Cordova, California 95670 <br />