ENV-17-27 Refinery 1-hour SO2 NAAQS Non-Attainment SIP Air Quality Modeling Analysis Case Study

Description:

The current 1-hour National Ambient Air Quality Standard (NAAQS) of 75 parts per billion (ppb) for sulfur dioxide (SO2) was promulgated on June 22, 2010. Once a new NAAQS becomes effective, individual States have one year to recommend attainment or non-attainment status based either on ambient air monitoring data or on air quality modeling. In the case of the 1-hour SO2 NAAQS the initial timeline for the designation area status areas was due by June 22, 2011. Within two years of the effective date of the 1-hour SO2 NAAQS, the U.S. EPA was required to approve the States’ proposed designations by June 22, 2013. For areas not attaining the 1-hour SO2 NAAQS, States were required to submit State Implementation Plans (SIPs) within 18 months of the determination of non-attainment areas. In the case of the 1-hour SO2 NAAQS, that meant that non-attainment SIPs were to be developed by December 22, 2013. Due to insufficient 1-hour air monitoring information, the U.S. EPA granted a 1-year extension for designating areas as non-attainment, pushing the timeline for development of non-attainment SIPs out by an additional year.