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Peter MacNiohdl February 2,2009. DDJC Site Page 2 embodied in DTSC's recommendations, Therefore, the receptors should be identified as the adult and child residents and the industrial worker. 2. Section 5.1.4, Exposure Scenarios, page 5-3 The discussion in this section is 'incorrect.. Exposure scenarios are residential and industrial. The exposure assessment uses the chemical data to estimate the exposure point concentration for each receptor under an assumedexposurescenario. HERD recommends that either this section is deleted or accurately discussed under"Exposure Characterization." 3. Section 5.4.2, Risk and Hazard Index Estimates,page 5-5 Please revise the identified receptors in accordance with specific comment 91. 4. Section 5.4.4.1 and Table 5-4 The risk assessment shows that the exposure route that is driving the risk is dermal contact and yet, the risk-based concentrations are based solely on ingestion and excludes dermal contact for the residential scenario. This presents an underlying inconsistency in the development of risk-based concentrations. HERD's recommendation is to calculate the risk-based concentrations by applying exposure assumptions similar to what were applied in estimating the baseline risks. 5. Appendix C, Section 2, Problem Formulation,C-1 There seems to be some confusion between the elements of an ecological risk assessment and of a human health risk assessment. To illustrate, Problem Formulation is the first element in a quantitative or semi-quantitative ecological risk assessment. The elements of a human health risk assessment, on the other hand, are Identification of Chemicals of Potential Concern, Exposure Assessment, Toxicity Assessment, and Risk Characterization. Therefore, the discussion in Section 2 is incorrect and should be revised accordingly. 6. Appendix C, Section 2.1, Exposure Pathway Analysis, pages-3, C-2, 2 nd paragraph The term"chemical stressor" is used in ecological, not in human health, risk assessments. A source of chemical release is one of four factors that define a complete exposure pathway. This paragraph should be modified so that a complete exposure pathway is accurately discussed. 7. Appendix C,Section 2.4, page C-4 Please see specific comment 1 regarding the identified receptors and revise the 'text accordingly. 8. Appendix C,Table C-4 The parameters in this Table indicate that the adult:resident was the only receptor assumed to have dermal contact with groundwater. An age-adjusted ingestion factor was incorporated into