Air Plan Approval; Indiana; Regional Haze Plan and Prong 4 (Visibility) for the 2006 and 2012 PM2.5, 2010 NO2, 2010 SO2, and 2008 Ozone NAAQS

The Environmental Protection Agency (EPA) is taking action under the Clean Air Act (CAA) on Indiana's November 27, 2017 State Implementation Plan (SIP) submittal addressing regional haze. This action is based on EPA's previous determination that a state's implementation of the Cross-State Air Pollution Rule (CSAPR) program continues to meet the criteria of the Regional Haze Rule (RHR) to qualify as an alternative to the application of Best Available Retrofit Technology (BART). EPA is taking several related actions. First, EPA is approving the portion of Indiana's November 27, 2017 SIP submittal seeking to change reliance from the Clean Air Interstate Rule (CAIR) to CSAPR for certain regional haze requirements. EPA is also converting EPA's limited approval/limited disapproval of Indiana's regional haze SIP to a full approval and withdrawing the Federal Implementation Plan (FIP) provisions that address the limited disapproval. Finally, EPA is approving the visibility prong ("prong 4") of Indiana's infrastructure SIP submittals for the 2006 24-hour and 2012 annual fine particulate matter (PM<INF>2.5</INF>), 2010 nitrogen dioxide (NO<INF>2</INF>), and 2010 sulfur dioxide (SO<INF>2</INF>) National Ambient Air Quality Standards (NAAQS) and converting EPA's disapproval of the visibility portion of Indiana's infrastructure SIP submittal for the 2008 ozone NAAQS to an approval.