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Mr.Michael Oliphant—CEMC <br /> HHSE Addendum February 22,2012 <br /> Surland Homes-Bridle Creek Page 5 of 6 <br /> ' equal to or below this threshold is considered to be acceptable by the Cal/EPA and <br /> EPA. <br /> Non-Cancer Health Hazards <br /> ' The estimated oral and dermal hazards associated with individual COPCs, and the <br /> summation of hazards associated with all COPCs for these routes are provided in <br /> ' Table 23. The hazards from indirect inhalation exposure associated with individual <br /> COPCs, and the summation of hazards for all COPCs for the inhalation route are <br /> provided in Table 24. The aggregate non-cancer hazard for oral, dermal, and inhalation <br /> ' routes is provided in Table 25. SAIC estimated the total potential non-cancer hazard <br /> from oral, dermal, and inhalation exposures to on-site soils to be 0.1. This level of <br /> hazard is below the threshold hazard index of 1, and therefore indicates an acceptable <br /> ' non-cancer health hazard for exposures to on-site soils for a construction worker. <br /> SUMMARY AND CONCLUSIONS <br /> ' SAIC evaluated cancer risks and non-cancer hazards under three additional scenarios <br /> utilizing analytical data from borings B-1 through B-7 (Tables 1 through 3): residential <br /> scenario 1, residential scenario 2, and construction worker scenario. The cancer risks <br /> ' and non-cancer hazards were estimated using very conservative assumptions and <br /> methods. The actual cancer risks and non-cancer hazards are believed to be <br /> significantly lower. <br /> ' The excess cancer risks for both residential scenarios 1 and 2 were within, and at the <br /> lower end of, the risk management range of 1E-06 to 1E-04 established by the Cal/EPA <br /> and EPA. These are conservative estimates of risk, and should not result in <br /> ' unacceptable health risks for an adult or child resident. The cancer risk for the <br /> construction worker scenario was below the incremental lifetime cancer risk point of <br /> departure, and an excess cancer risk equal to or below this threshold is considered to be <br /> ' acceptable by the Cal/EPA and EPA. <br /> The non-cancer hazards for all three scenarios were below the threshold hazard index <br /> of 1, and therefore indicate an acceptable non-cancer health hazard for exposures to on- <br /> site soils for a hypothetical resident under all three scenarios. <br /> The results of this HHSE addendum indicate that exposure to chemicals present in soil <br /> at the Site should not result in unacceptable health risks for an adult or child on-site <br /> resident, or for construction workers. Therefore, no remedial action is necessary at the <br /> Site to protect human health, and a risk management decision of no further action can <br /> be made for on-site affected soils. <br /> Sincerely, <br /> ' SAIC Energy,Environment& Infrastructure,LLC <br /> \S.��gEU <br /> r <br /> MICHAEL HURD r <br /> No. 0068 <br /> Michael Hurd,CHG 0068 CER11FIE6 <br /> HYDROGEOLOGI57 <br /> EXP. <br /> �T4Tf OF CAC\f6��`p <br />