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• • <br /> workers have a greater potential for increased exposure to airborne <br /> dusts due to excavation activities and/or movement of trucks and other <br /> construction equipment on unpaved roads. A PEF for the construction <br /> worker scenario may be calculated using the methods outlined in the <br /> Supplemental Guidance for Developing Soil Screening Levels for Superfund <br /> Sites (US EPA, 1999) . Alternately, the Cal EPA recommended value of <br /> 1, 000 µg/m3 for construction workers may be used. <br /> 15. Table 3-6, Page 3-3: The footnote for this table, which discusses <br /> dermal absorption efficiency, appears to belong to Table 3-5. Please <br /> correct the text. <br /> 16. Section 3 .1.4.2, Page 3-4: The final sentence states that carcinogenic <br /> risk is the "probability of an individual developing cancer over a <br /> lifetime of exposure. " This statement is incorrect. The exposure <br /> durations evaluated in the risk assessment are, respectively, 25 years <br /> for an industrial worker and one year for a construction worker. These <br /> are not "lifetime" exposure durations. Because carcinogens are presumed <br /> to act via a genotoxic mechanism, the effects can persist even after <br /> exposure has ceased. For this reason, the carcinogenic effects are <br /> averaged over the lifetime of the receptor, regardless of the presumed <br /> exposure duration. Please correct the text in this section. <br /> 17. Section 3.1.4.4, Page 3-4: The final sentence in this section, as well <br /> as the text in Section 3.3.4, should be moved to the conclusion of the <br /> Report. Such statements regarding whether a specific risk level is <br /> significant or indicates a concern represent risk management <br /> conclusions. US EPA guidance on risk assessment and risk <br /> characterization (US EPA, 1995) clearly states the need to separate risk <br /> assessment from risk management. Please revise the text appropriately. <br /> 18. Table 3.7, Page 3-5: The values presented in this table for a <br /> hypothetical industrial worker appear to have been added incorrectly. <br /> According to the values shown for ingestion and dermal risks for DDE, <br /> the total should be 2 .5E-08, not 1.0E-07 as shown. If the total risk <br /> for DDE is 1. 0E-07 as indicated in the table, then the total risk for <br /> the hypothetical industrial worker should be 1.2E-06, not 2.9E-07. <br /> Please review and correct the values shown in Table 3-7. <br /> 19. Section 4.2, Page 4-1: The Report states that the entire volume of soil <br /> affected by chlordane, endrin and selenium was likely removed during <br /> excavation associated with the storm drain. However, the Report does <br /> 6 <br />