March 16, 2021 Michael S. Regan, Administrator Office of the Administrator (1101A) United States Environmental Protection Agency William Jefferson Clinton Building 1200 Pennsylvania Avenue, N.W. Washington, DC 20460 Re: Regional Haze Guidance Petition for Reconsideration: Priority Issues Dear Administrator Regan: National Parks Conservation Association, Sierra Club, the Coalition to Protect America’s National Parks, Appalachian Mountain Club,