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Page 2 of 2 <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 (V1 through V9) at 4 feet below <br /> ground surface (bgs) from the site (Figure 1). Soil Gas analytical results are shown in Table 1. Total <br /> volatile petroleum hydrocarbons (TVPH) were detected at 1,810 and 92 parts per million by volume <br /> (ppmv) in V5 and V6, respectively, located to the immediate north of the service shop building. Benzene <br /> was detected at 5.4 and 0.17 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 <br /> Table 2. It is apparent that the maximum detected concentrations of benzene and MTBE exceed both the <br /> residential and 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 <br /> Table 3. It is apparent that the maximum detected concentrations of benzene and MTBE exceed the <br /> residential and 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 <br /> use of the site,the assessment of soil gas intrusion to indoor air was conducted for a commercial scenario. <br /> The results of J&E modeling are summarized in Table 4. It is apparent that the residential and commercial <br /> cancer risks exceed 1 in 1 million (1E-06) by more than an order of magnitude. Therefore, the cancer risk <br /> calculated using the maximum detected concentrations of chemicals detected in soil gas would not be <br /> considered as acceptable. <br /> Conclusion <br /> The HHRH confirmed that the 2000 soil gas concentrations represent an unacceptable health risk when <br /> compared to ESLs, CHHSLs, and analysis using the J&E Model. In the letter dated October 11, 2010, the <br /> SJCEHD approved collection of new soil gas data if the risk was unacceptable using the 2000 soil gas <br /> concentrations. AA&A will proceed to collect additional soil gas samples in accordance with our workplan <br /> dated August 26, 2010 and approved by the SJCEHD on October 11, 2010. <br /> Information contained in this email has been reviewed and approved by our Board Certified Toxicologist <br /> and our Professional Geologist. <br /> Regards, <br /> Dinesh Rao <br /> Senior Project Manager <br /> AMI ADINI &ASSOCIATES, INC. <br /> 4130 Cahuenga Blvd, Ste 113 <br /> Los Angeles, CA 91602 <br /> Tel # (818) 824-8102 <br /> Fax# (818) 824-8112 <br /> e-mail: dineshCcilamiadini.com <br /> www.amiadini.com <br />