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EPA Proposes Area Designations and Outlines Implementation Approach for 1-hour SO2 NAAQS

Posted Monday, February 18th, 2013

In two related actions, the U.S. Environmental Protection Agency (EPA) has proposed initial nonattainment areas for the 2010 1-hour Sulfur Dioxide (SO2) National Ambient Air Quality Standard (NAAQS) and outlined the next steps in its approach to characterizing remaining areas.  EPA’s proposed initial nonattainment area designations are based on previously submitted state recommendations and the most recently available monitoring data.  For Florida, as recommended by the Florida Department of Environmental Protection, EPA has proposed designating portions of Hillsborough and Nassau Counties as nonattainment.  Per notice published February 15, 2013, comments on EPA’s proposed nonattainment designations must be submitted by March 18, 2013.  Final designations are expected in June 2013.  Additional information regarding EPA’s proposed nonattainment designations is available here.

While EPA is proposing initial nonattainment designations based on available monitoring data, the agency has explicitly stated it is not proposing designations for other areas, which EPA will address in future actions.  For these other areas, EPA has issued a February 6, 2013, “next steps” document outlining the anticipated approach to making future area designations.  Previously, in the preamble to the 2010 1-hour SO2 NAAQS and in subsequent guidance issued in 2010, EPA indicated it expected modeling-based state implementation plans demonstrating maintenance and attainment of the standard.  EPA subsequently retreated from this position, however, and initiated stakeholder outreach to help refine its approach and determine the appropriate role of modeling (instead of traditional monitoring) in making nonattainment area designations for the 1-hour SO2 NAAQS.  The approach outlined in EPA’s February 6, 2013, next-steps document represents the culmination of these outreach efforts.

In its next-steps document, EPA states that instead of requiring modeling, implementation will focus on monitoring while retaining modeling as an option.  In addition, EPA states that it plans to utilize a “two-pronged” emission threshold approach to identifying currently unclassifiable areas for additional modeling, monitoring, or some combination thereof.  This two-pronged approach would include lower emission thresholds for sources in more densely populated areas (2,000-3,000 tons per year) and higher emission thresholds for less populated areas (5,000-10,000 tons per year).  EPA also states that rather than merely issuing guidance, it plans to develop its approach to implementation through rulemaking.

Finally, EPA’s next-steps document also lays out the anticipated timeline for future action, which includes the following major milestones:
(1) Late 2013 – EPA proposes a “data requirements” rule directing agencies to characterize air quality by date certain for areas covered by relevant thresholds.  This rule would also set milestones leading to eventual area designations, whether based on monitoring or modeling.  EPA notes that finalizing area designations from monitoring will take longer than modeling because of the time needed to site new monitors and collect three years of monitor data.  

(2) Late 2014 – EPA finalizes its “data requirements” rulemaking.

(3) 1/2016 – Sources are identified for deployment of new monitors, and modeling protocols are submitted for sources that are to be modeled.

(4) 1/2017 – New monitors are deployed and operational; modeling analysis and associated modeling-based nonattainment area recommendations are submitted to EPA.  As an alternative, EPA states that agencies may submit enforceable emission limitations demonstrating attainment to avoid a nonattainment designation.

(5) 12/2017 – EPA issues final designations for modeled areas.

(6) 8/2019 – SIP attainment demonstrations are due for modeled-nonattainment areas.

(7) 5/2020 – Monitor-based area designation recommendations are submitted to EPA.

(8) 12/2020 – EPA issues final designations for monitored areas.

(9) 8/2022 – SIP attainment demonstrations are due for monitored-nonattainment areas.

Additional information regarding implementation of the 2010 1-hour SO2 NAAQS is available on EPA’s website here.

For additional information, contact Joseph Brown.

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