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1 <br /> ' Mr.Michael Oliphant—CEMC <br /> HHSE Addendum February 22,2012 <br /> Surland Homes-Bridle Creek Page 4 of 6 <br /> ' with individual COPCs, and the summation of inhalation risks are provided in Table 15. <br /> The aggregate risks for oral, dermal, and inhalation cancer risks are provided in <br /> Table 16. SAIC estimated the total potential cancer risk to a hypothetical resident from <br /> ' oral, dermal, and inhalation exposures to on-site soils to be 2E-06. This level of risk is <br /> within, and at the lower end of,the risk management range of 1E-06 to 1E-04 <br /> established by the Cal/EPA and EPA. The largest contributors to the excess cancer risk <br /> ' are benzo(a)pyrene, benzo(b)fluoranthene, and nickel. <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 17. 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 18. The aggregate non-cancer hazard for oral, dermal, and inhalation <br /> routes is provided in Table 19. SAIC estimated the total potential non-cancer hazard <br /> from oral, dermal, and inhalation exposures to on-site soils to be 0.4. 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 hypothetical resident. <br /> ' CONSTRUCTION WORKER SCENARIO <br /> As with the 2009 HHSE, SAIC calculated the EPCs as the upper confidence limit <br /> (UCL) of the mean soil concentration for each of the COPCs. SAIC used the most <br /> ' current version of the EPA statistical software program, ProUCL Version 4.00.054, to <br /> analyze the datasets provided in Tables'l through 3. SAIC used the sample median in <br /> this HHSE addendum to represent the EPC for toluene, ethylbenzene, total xylenes, and <br /> ' benzo(k)fluoranthene, as recommended in the ProUCL User's Guide,because the <br /> detection frequency was too low to calculate a UCL. SAIC utilized the same <br /> methodology,toxicity criteria(Tables 5 and 6), and exposure parameters(Table 7) as <br /> ' were utilized for the construction worker scenario in the 2009 HHSE; however, only <br /> data collected from borings advanced in the UPRR ROW were used in this HHSE <br /> addendum. <br /> MCancer Risks <br /> The estimated oral and dermal cancer risks associated with the individual COPCs, and <br /> ' the summation of cancer risks associated with all COPCs for these exposure routes are <br /> provided in Table 20. The estimated risk from indirect inhalation exposure associated <br /> with individual COPCs, and the summation of inhalation risks are provided in Table 21. <br /> The aggregate risks for oral, dermal, and inhalation cancer risks are provided in <br /> Table 22. SAIC estimated the total potential cancer risk to a construction worker from <br /> oral, dermal, and inhalation exposures to on-site soils to be 5E-08. This level of risk is <br /> ' below the incremental lifetime cancer risk point of departure, and an excess cancer risk <br /> ' 4. EPA,2010. Pro UCL Version 4.00.05(Statistical Software to Compute Upper Confidence Limits of the Unknown <br /> Population Mean),National Exposure Research Laboratory Environmental Sciences. EPA/600/R-07/035. <br /> May. <br />