Partial Approval and Partial Disapproval of Air Quality State Implementation Plans; Arizona; Infrastructure Requirements for Nitrogen Dioxide and Sulfur Dioxide

The Environmental Protection Agency (EPA) is partially approving and partially disapproving several state implementation plan (SIP) submissions from the State of Arizona pursuant to the requirements of section 110(a)(1) and 110(a)(2) of the Clean Air Act (CAA or "the Act") for the implementation, maintenance, and enforcement of the 2010 nitrogen dioxide (NO<INF>2</INF>) and 2010 sulfur dioxide (SO<INF>2</INF>) national ambient air quality standards (NAAQS or "standards"). We refer to such SIP submissions as "infrastructure" SIP submissions because they are intended to address basic structural SIP requirements for new or revised standards including, but not limited to, legal authority, regulatory structure, resources, permit programs, monitoring, and modeling necessary to assure implementation, maintenance, and enforcement of the NAAQS. In addition, the EPA is reclassifying Pima County from Priority II to Priority III for SO<INF>2</INF> emergency episode planning purposes. The EPA is also approving into the Arizona SIP sections of an Arizona Revised Statute related to air quality modeling and the submission of modeling data to the EPA. Finally, the EPA is clarifying several inconsistencies between its technical support document and notice of proposed rulemaking.