Recent Court Case Sets 1-Hour SO2 NAAQS and Air Quality Modeling Precedent

The U.S. Court of Appeals for the Third Circuit Court recently upheld a U.S. EPA rule that established a sulfur dioxide (SO₂) emission limit on a coal-fired power plant in eastern Pennsylvania.  Specifically, U.S. EPA used air quality modeling to show that the coal-fired power plant was contributing to a 1-hour SO₂ NAAQS violation in New Jersey and also used air quality modeling to establish SO₂ emission limits that would show compliance with the 1-hour SO₂ NAAQS.  This court decision will become important as states move forward with implementing the 1-hour SO₂ NAAQS as it will provide precedent for U.S. EPA to address individual SO₂ emission sources.  In addition, individual source 1-hour SO₂ NAAQS exceedances could be identified through air quality modeling as a part of local source modeling completed in accordance with the Prevention of Significant Deterioration (PSD) construction permitting process or air quality modeling completed by environmental groups.

What is the current status of the 1-hour SO₂ NAAQS implementation process for areas without SO₂ monitors?

Currently, U.S. EPA is reviewing comments submitted (the comment period ended on July 22, 2013) on the draft “SO₂ NAAQS Modeling Technical Assistance Document” and the “Source-Oriented SO₂ Monitoring Technical Assistance Document.”

U.S. EPA currently intends to issue final versions of the documents by the end of 2013.  U.S. EPA then intends to identify those sources and areas that will deploy new monitors or that will be subject to air quality modeling in 2015 with monitoring and modeling protocols submitted in 2016.  Finally, monitors will be deployed and air quality modeling initiated in January 2017.