The Environmental Protection Agency proposes to revise the Federal Implementation Plan under the Clean Air Act for Oil and Natural Gas Well Production Facilities on the Fort Berthold Indian Reservation (Mandan, Hidatsa and Arikara Nation) in North Dakota, known as the FBIR FIP. The proposed revisions since the FBIR FIP was promulgated in 2013 (78 FR 17836) and subsequently revised in 2015 (80 FR 16564) would clarify compliance-related aspects of the rule and add provisions to improve enforceability. These revisions would further improve basic air quality regulations resulting in the protection of human health and the environment for communities in and adjacent to the Fort Berthold Indian Reservation. The FBIR FIP, as revised, will continue to be implemented by the EPA or the Mandan, Hidatsa and Arikara Nation, if delegated authority.