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Peter MacNichotl. February 2,:2009 DD.1C site. Page 3 the ingestion dose equation whereas an age-adjusted dermal factor was not. In evaluating the residential scenario, a skin surface area of 6600 cmc for a child resident should be included in the dermal dose equation or in deriving an age-adjusteddermal'factor. CONCLUSIONS The discussion on the human health risk assessment contains inaccuracies that are identified in the preceding specific comments. An adequate understanding of each component in a health risk assessment will resolve these deficiencies. HERD concurs that all the risk estimates exceeded the point of departure of 1 E-06 under both residential and industrial scenarios. HERD does not agree with the approach of developing risk-based concentrations for the residential scenario based solely on groundwater ingestion. The forward evaluation assumed complete exposures via ingestion and dermal contact. Considering that the primary contributor to the cumulative risk is the dermal pathway, elimination of this pathway in developing health protective concentrations in groundwater is invalid. As noted in specific comment #9, the evaluation of the hypothetical resident's exposures via domestic use of groundwater should Include both adult and child receptors. Therefore, inclusion of the dermal pathway could potentially result in risk-based concentrations lower than the range of 0.004 to 0.4 ug/L for the residential scenario, The selected alternative is the implementation of land-use controls on groundwater use and installation of water production wells. HERD defiers to the risk managers for concurrence on the proposed alternative. However, HERD recommends that the human health risk assessment be revised to address the deficiencies. Reviewed by ,Michael Jlade, Ph.D; DABT i� Senior Toxicologist t