States are Planning to Model Major Facilities for SO2

U.S. EPA promulgated a final 1-hour sulfur dioxide (SO₂) National Ambient Air Quality Standard (NAAQS) on June 22, 2010. The new 1-hour NAAQS became effective on August 23, 2010. As described in ALL4’s May 2010 4 The Record, the new 1-hour NAAQS is extremely stringent and will become a critical issue for new air quality permitting projects, particularly those projects that trigger Prevention of Significant Deterioration (PSD) requirements for SO₂. As part of the implementation of the 1-hour SO₂NAAQS, U.S. EPA revised their originally proposed approach for establishing NAAQS designations (i.e., attainment versus nonattainment areas). Instead of using a new network of ambient monitors to establish designations, U.S. EPA has proposed to use facility-specific air dispersion modeling, an approach that would place a burden on individual facilities to demonstrate compliance with the NAAQS even in the absence of a PSD-triggering project. At the time of the NAAQS promulgation, deadlines for the air quality modeling demonstrations were only generally tied to the June 2013 deadline for states to revise their State Implementation Plans (SIPs), and it was difficult to tell when individual facilities may expect to see activity in their states. Since the NAAQS promulgation, there have been a few examples of states and individual facilities beginning to compile air quality modeling data in support of the SO₂ NAAQS designations. One such example is the Illinois Environmental Protection Agency (IEPA), which communicated to select major facilities in late August that they would be performing air quality modeling for those facilities and requested source specific information from them in order to complete the modeling evaluation. IEPA correspondence is an example of what we can expect to see throughout the country as other states develop their plans to implement the SO₂ NAAQS. This first of many state actions to come underscores the importance in certain cases of gaining an early understanding of how your existing operations compare to the 1-hour NAAQS level.