The purpose of this Notice of Proposed Rulemaking (NPRM) is to solicit broad feedback on the most effective and efficient means of promulgating a Clean Air Act (CAA) Federal Implementation Plan (FIP) applicable to sources on Indian country lands within the Uintah and Ouray Indian Reservation (U&O Reservation) to establish a bank of ozone-precursor emission reduction credits (ERCs) that may be generated and used for several air quality planning purposes. Specifically, the credits could be utilized in achievement of the ozone National Ambient Air Quality Standard (NAAQS), general conformity demonstrations, and new source review (NSR) permitting related to development of new ozone-precursor emissions sources in the Uinta Basin Ozone Nonattainment Area in Utah. The EPA designated portions of the physiographic region known as the “Uinta Basin” nonattainment for the 2015 Ozone NAAQS, effective August 3, 2018. This NPRM discusses potential approaches to credit reductions of ozone precursor emissions from existing sources in Indian country within the Uinta Basin Ozone Nonattainment Area to be used for several purposes.