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Cori L. Condon - 2 - 15 December 1997 Discussion: Other than a footnote at the bottom of page 12, ATSDR's revised report does not acknowledge methods other than their own for evaluating health risks associated with chemicals in groundwater. Violations of California MCLs in domestic wells are labeled as posing no health risk. California cancer potency factors and risk assessment methods which differ from ATSDR's have not been cited in the revised report. The ATSDR public review draft report is internally inconsistent. Even where ATSDR's risk assessment methods indicate an unacceptable risk, the report states otherwise. The report states in numerous locations that, in ATSDR's estimation,no public health hazards exist at or in the vicinity of the Sharpe Depot. Even so, the "Public Health Action Plan" on page 19 of the report recommends that off-site private wells be continued to be monitored and that alternative water sources be provided if MCLs are shown to be exceed. The following is a list of errors and omissions noted in the earlier draft ATSDR report along with a discussion in italics of how each issue was answered in the public review draft report: • Page 33. The summary table of VOC concentrations in off-site private wells does not include data for 1,2-DCA. DCA data has been added to the table, which now appears on page 31. • Page B-3,¶ 3. ATSDR's calculated lifetime cancer risk from arsenic exposure to on-site workers of 6.16 x 10-4 is not within the Superfund residual risk range of 10-4 to 10-6, as claimed. The statement has been changed to say that the calculated risk "slightly exceeds the acceptable range"while, in fact, the calculated risk is over six times the least protective end of the Superfund risk range. The report also ignores their own acceptable risk criteria by continuing to state that "ATSDR does not consider workers to beat increased risk of developing cancer." Their analysis raises issues of credibility. • Page B-4,14. EPA has classified PCE in weight-of-evidence category B2 or probable human carcinogen. The ATSDR report incorrectly labels PCE as a probable or possible human carcinogen. The report has been corrected in response to this comment. • Page B-5,$ 1. The California Primary MCL for 1,2-DCA is 0.5 µg/1,not 5 µg/1. Measured concentrations of 1,2-DCA in private off-site wells have significantly exceeded this drinking water standard. The California MCL citation has been�orrected. However, the report still claims that 1,2-DCA concentrations which consistently exceed the MCL and range as high as 40-times the MCL (not the 'four times"stated in the report[page B-5, ¶ 5]) in this domestic well are "unlikely to pose a public health hazard. " Had the well served 25 or more connections, rather than a single residence, the water purveyor would be legally barred from delivering this water to consumers in California under the Health and Safety Code. Once again, ATSDR's analysis raises issues of credibility. • Page B-5,¶ 1. The report discusses MCLs as "enforceable." Primary MCLs are enforceable drinking water standards for chemicals in water distribution systems and at the tap. In groundwater and other ambient waters,water quality objectives from the applicable Basin Plan are part of the enforceable water quality standards. By reference, Primary and Secondary MCLs are a subset of the enforceable water quality standards for chemical constituents in groundwater in the area of DDRW