Region 8

Wind River Treatment in the Same Manner as a State Approval

February 13, 2014 update: On February 13, 2014, EPA agreed to temporarily stay the effect of its Wind River Reservation boundary determination for purposes of the Eastern Shoshone and Northern Arapaho Tribes’ implementation of non-regulatory provisions of the Clean Air Act.   The stay will apply to the City of Riverton, among other areas.  EPA’s action is responsive to requests received from both Tribes and the State. EPA anticipates the resolution of the Reservation boundaries in the courts and will continue to work with the Tribes to move forward on Clean Air Act activities in areas that are not disputed by the State of Wyoming.


On December 6, 2013, EPA approved the Northern Arapaho and Eastern Shoshone Tribes’ application to administer certain non-regulatory provisions of the Clean Air Act on the Wind River Indian Reservation. EPA’s approval will further the Tribes’ Clean Air Act grant funding capabilities, allow them to receive notifications of certain air permits that may affect their airshed, and allow for their participation in air quality commissions and in the development of risk management plans.

The Clean Air Act and EPA’s regulations also require the Agency to make a determination regarding the Wind River Indian Reservation boundaries.  After carefully evaluating relevant statutes and case law, historical documents, the Tribes’ application materials, all public comments, and input from other federal agencies, EPA has made a determination regarding the Reservation boundary.  This determination is consistent with a 2011 Opinion of the Solicitor of the U.S. Department of the Interior.  EPA will work closely with the Tribes and the State of Wyoming to identify and resolve any program implementation issues related to the Reservation boundaries and ensure the protection of public health and the environment. 

EPA’s approval is based on a thorough analysis of the Tribes’ application, public comments, the 2011 DOI Solicitor’s Opinion, relevant information, and the eligibility requirements specified under the Clean Air Act.  More information can be found below.

For further information regarding EPA’s TAS Decision, please contact Carl Daly at 303-312-6416.