The Environmental Protection Agency (EPA) is proposing approval of regulatory revisions to the Arizona Department of Environmental Quality (ADEQ) portion of the applicable state implementation plan (SIP) for the State of Arizona. These revisions are primarily intended to make corrections to ADEQ's SIP-approved rules for the issuance of New Source Review (NSR) permits for stationary sources, with a focus on preconstruction permit requirements under the Clean Air Act (CAA or Act) for major sources and major modifications. On November 2, 2015, we took final action on a SIP submittal from ADEQ that significantly updated ADEQ's SIP-approved NSR permitting program. However, that action identified several deficiencies in ADEQ's program that needed to be corrected. This proposed action will correct a substantial portion of the deficiencies we identified in that 2015 action. We are seeking comment on our proposed action and plan to follow with a final action.