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that addressed issues of particular importance to the RI/FS are briefly reiterated, and in some cases expanded upon, below. Page references to the Supplementary Soil Investigation Plan are provided in parentheses. 16. SHAD states that the groundwater pathway has been qualitatively identified as representing the most significant risk to human health, and contends that direct exposure to contaminated soil and inhalation of dust (from contaminants already identified) do not represent significant human health or environmental risks (pg. 3-2, paragraph 1). The plan cites a study that was then in preparation to support this claim, but the cited report was not referenced in the list of references. What is the basis for the conclusion? 17. Regarding the significance of the risk from exposure to soils, it is not possible to evaluate the health risks from exposure to soils that have not been adequately characterized. Since one of the purposes of the supplemental soil investigation is to characterize those soils, it appears that SHAD is making a circular argument in recommending that future characterization of soil contamination should be restricted to compounds already identified in soils, or to those identified in another medium (groundwater). The sampling plan should target compounds that are known to have been used, stored, or disposed of at a particular site. 18. SHAD contends that all of the contaminants at certain sites (the fire -training area is the only example provided) were introduced into the environment in the same manner and therefore would be expected to have the same spatial distributions (pg. 3-2, paragraph 2). We agree that all information available to SHAD should be used if it may help narrow the search for contaminant compounds and may provide clues as to their distribution at specific potential source areas. But field verification of assumptions about the types and distributions of compounds is still required. Compounds with low attenuations in soil, such as TCE and other solvents can be expected to reach groundwater long before compounds that are of greater concern in terms of health risk such as dioxins, PCBs, chlorinated phenols, pesticides, polycyclic aromatic hydrocarbons (PAHs), heavy metals and many others expected to be present in some areas of the depot. (See preceding comment.) 8