SITE INFORMATION AND CORRESPONDENCE

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SPECIFIC COMMENTS 1. Section 1.3.3.4, Baseline Ecological Risk Assessment, Page 1-4: The summary indicates that the post-excavation soil samples collected from SWMUs 2 and 3 had DDX concentrations greater than the cleanup level established by the ROD. It is further indicated that the exposure and toxicity assumptions used to derive the ROD clean up levels were re-evaluated in the ESD. The text does not clearly indicate the reasons that the original clean up level was unable to be achieved during by the remedial action performed at the site. It has not been clearly justified as to why the original exposure and toxicity assumptions were considered appropriate at the time of the ROD, however, are now considered overly protective. Revise the report to clarify why the clean up levels could not be met. 2. Section 1.3.3.5, Baseline Ecological Risk Assessment, Page 1-4: It is indicated that the ROD assumed that the diet of the killdeer consisted of 100% earthworms, while conversely the ESD assumed 75% flying invertebrates for the re-evaluation. The rationale provided indicates that it is probably overly conservative to assume that the killdeer would consume only earthworms, since the bioaccumulation factor(BAF) associated with earthworms would be much greater than assumptions for other invertebrates. It is not evident that the specific assumptions for the killdeer are representative for other birds within this functional feeding group, that were intended to be represented by the killdeer. It is also not clear whether the killdeer was intended to represent other vermivore species (e.g., songbirds) which would be expected to consume a higher percentage of earthworms. Revise the document to clarify how the assumption is protective of all species within the functional feeding guild represented by the killdeer, and that other vermivore species are not expected to use the site. 3. Section 1.3.3.6, Baseline Ecological Risk Assessment, Page 1-4: It is stated, "the cleanup standard for DDX has been deleted from the remedy as documented in the ESD." It is further indicated that the re-calculated hazard quotients "are interpreted not to present a biologically significant risk." It is not clear whether the ESD is final and has been approved by regulatory agencies or whether the interpretation of risk was agreed by all risk managers at the site. Revise the document to provide the full citation for the ESD, and indicate whether the ESD has been finalized and approved, and clarify that biological significance was determined by consensus by all risk managers. 2