Document VKODRpG07azrL9v4MqKBex9ej

American* ^ Chemistry Council September 26, 2017 SUBMITTED VIA EMAIL Mr. Samuel Hernandez U.S. Environmental Protection Agency Office of Ground Water and Drinking Water 1200 Pennsylvania Ave., NW Washington, D.C. 20460 RE: Request for comment period extension on the draft report titled, "Proposed Approaches to Inform the Derivation of a Maximum Contaminant Level Goal for Perchlorate in Drinking Water" (draft MCLG Approaches Report; 82 FR 43354; EPA-HQ-OW-2016-0438) Mr. Hernandez: The American Chemistry Council (ACC) respectfully requests that EPA extend the comment period on the draft report, "Proposed Approaches to Inform the Derivation of a Maximum Contaminant Level Goal for Perchlorate in Drinking Water," by 45 days to December 14, 2017. We appreciate EPA's responsiveness in addressing the recommendations made by the first peer review panel in January 2017. However, given the complexity and length of the revisions in the Biologically Based Dose-Response (BBDR) model and supporting documentation being used to develop the MCLG, a 90-day comment period is necessary to allow sufficient time for public review and comment All parties, but especially the second peer review panel, will benefit from additional time to evaluate the changes and technical assumptions in the updated BBDR model. We would appreciate a response to this request at your earliest convenience. Should you have questions or would like to discuss this request, please contact me at iudith nordgren@americanchemistry.com or Mark Gibson at mark gibson@americanchemistry.com. Sincerely, cc: Michael Shapiro - EPA, 0W Lee Forsgren - EPA, 0W Peter Grevatt- EPA, 0GWDW Eric Burneson - EPA, OGWDW Judith Nordgren Managing Director Chlorine Chemistry Division americanchemtstry.com Sierra Club v. EPA 18cv3472 NDCA 700 Second St.. HE | Washington, DC 2.0002. | (202.) 249-7000 Prod 1 ED 002061 00098698-00001