4 The record articles

U.S. EPA Provides SO2 NAAQS “Implementation” Guidance

Posted: April 4th, 2011

Author: All4 Staff 

On March 25, 2011, U.S. EPA released guidance on the implementation process for the 1-hour sulfur dioxide (SO2) National Ambient Air Quality Standard (NAAQS). The 1-hour SO2 NAAQS was promulgated in June 2010. As part of the NAAQS implementation process, states need to make attainment and nonattainment designations (i.e., determinations of which areas are, or are not, in compliance with NAAQS) and submit them to U.S. EPA for approval. Although these designation decisions are typically based on a review of ambient monitoring data, U.S. EPA has recommended that the 1-hour SO2 NAAQS designations should also rely on facility-specific air dispersion modeling. The use of dispersion modeling for the designation process has far reaching impacts on industry (see ALL4’s May 2010 4 The Record article entitled “Not So Fast – Getting That Air Permit Won’t Be As Easy As You Think” and July 2010 4 The Record Extra! entitled “Implementation of the New SO2 NAAQS Through Modeling”). Modeling performed by individual facilities to demonstrate NAAQS compliance could result in the requirement to implement emission reductions or process changes that would need to be implemented by 2017. Several states are already performing air dispersion modeling for individual facilities and the remaining states will follow after U.S. EPA releases additional guidance in the early summer time frame. Any facility that has the potential to emit (PTE) greater than 100 tons per year of SO2 is likely to be required to perform modeling. ALL4 recommends that facilities plan ahead for the potential impacts of 1-hour SO2 air dispersion modeling. Stay tuned to 4 The Record for continued updates on the 1-hour SO2 NAAQS implementation process.


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