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Page 1 of 2 <br /> Vicki McCartney [EH] <br /> From: Dinesh Rao[dinesh@amiadini.com] <br /> Sent: Tuesday, December 14, 2010 4:44 PM <br /> To: Vicki McCartney[EH] <br /> Cc: 'Ami Adini; 'Gabriele Baader' <br /> Subject: FrontierTransport_p01_HHRA Results <br /> Attachments: FrontierTransport_p01_HHRA_Figure 1_SoilGasProbeLocations.pdf; <br /> FrontierTransport_p01_HHRA_Tables 1-4.pdf <br /> Dear Ms. McCartney: <br /> Ami Adini & Associates. Inc., (AA&A) completed a Human Health Risk Assessment (HHRA) for the Frontier <br /> Transportation site located at 425 Larch Road in Tracy, California (Figure 1). The HHRA was completed based <br /> on soil gas concentrations dated January 2000. This HHRH was prepared in response to a directive by the San <br /> Joaquin County Environmental Health Department(SJCEHD)as stated in a letter dated October 11,2010. <br /> The HHRH was completed using the following methodologies: <br /> • Comparison of the maximum concentration of each detected chemical to the 2008 Environmental <br /> Screening Levels(ESLs)established by the San Francisco Bay Regional Water Quality Control Board <br /> • Comparison of the maximum concentration of each detected chemical to the 2010 California Human <br /> Health Screening Levels (CHHSLs) established by Office of Environmental Health Hazard Assessment <br /> (OEHHA)for California Environmental Protection Agency. <br /> • Modeling using the Department of Toxic Substances Control (DTSC) version of the Johnson and <br /> Ettinger Model(J&E Model) <br /> In January 2000, soil gas samples were collected from nine vapor probes (V 1 through V9) at 4 feet below ground <br /> surface (bgs) from the site (Figure 1). Soil Gas analytical results are shown in Table 1. Total volatile petroleum <br /> hydrocarbons (TVPH) were detected at 1,810 and 92 parts per million by volume (ppmv) in V5 and V6, <br /> respectively, located to the immediate north of the service shop building. Benzene was detected at 5.4 and 0.17 <br /> ppmv in V5 and V6,respectively. <br /> Comparison with ESLs <br /> The comparison of maximum detected concentrations of each chemical of concern to ESLs is shown in Table 2. It <br /> is apparent that the maximum detected concentrations of benzene and MTBE exceed both the residential and <br /> commercial ESLs for these chemicals. <br /> Comparison with CHHSLs <br /> The comparison of maximum detected concentrations of each chemical of concern to CHHSLs is shown in Table <br /> 3. It is apparent that the maximum detected concentrations of benzene and MTBE exceed the residential and <br /> commercial CHHSLs for these chemicals. <br /> J&E Modeling <br /> The evaluation of vapor intrusion to indoor air was conducted using the J&E Model.Based on location and use of <br /> the site,the assessment of soil gas intrusion to indoor air was conducted for a commercial scenario. The results of <br /> J&E modeling are summarized in Table 4. It is apparent that the residential and commercial cancer risks exceed 1 <br /> in I million (1E-06) by more than an order of magnitude. Therefore, the cancer risk calculated using the <br />