Jack C. Bender
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EPA Close to Completing Area Designations for 2015 8-Hour Ozone Standard

April 27, 2018Newsletters
The AIR QUALITY Letter: April 2018

On November 16, 2017, EPA published a final rule establishing its initial air quality designations for most areas of the United States for the 2015 primary and secondary national ambient air quality standards (NAAQS) for ozone. In that action, EPA designated 2,646 counties as attainment or attainment/unclassifiable for the 2015 ozone standard. The 2015 ozone standard reduced the 8-hour ozone NAAQS from 75 parts per billion (ppb) to 70 ppb. The designation process will be completed when EPA issues its final rule designating nonattainment areas for the 2015 ozone standard.

EPA was required by the Clean Air Act to promulgate final designations for the 2015 ozone standard by October 1, 2017. EPA initially sought to delay implementation of the ozone standard by one year in a formal notice published in the Federal Register in June 2017. Litigation ensued and a court order in the ozone designation litigation, entered March 12, 2018, required EPA to promulgate final designations for the remainder of the country (with the exception of the San Antonio area) by no later than April 30, 2018. Final designations for the San Antonio area are required by July 17, 2018. While EPA ultimately withdrew the plan for the delay in implementation, it originally sought the delay in part to provide time for new agency officials to review and potentially reconsider the 2015 ozone NAAQS. At this time, EPA is reportedly still evaluating whether it will formally reconsider the 2015 Ozone Standard.

On March 8, 2018, EPA issued a final rule establishing the air quality thresholds that define the classifications that will be assigned to nonattainment areas for the 2015 ozone NAAQS. The final rule also establishes the attainment deadlines for each nonattainment area classification. Ozone nonattainment areas are being classified into five classifications ranging from “marginal” to “extreme” dependent on severity of the ozone problem based upon monitoring data. Attainment deadlines for each nonattainment area classification will range from three years from the effective date of the designation for marginal areas to 20 years from the effective date of the designation for extreme areas. The final nonattainment designations that will be made by EPA by April 30 will place each designated area within one of these five classifications.

EPA must also finalize an implementation rule for states to use in developing implementation plans for designated nonattainment areas. In conjunction with the implementation rule, EPA has indicated it will develop important permitting guidance on significant impact levels (SILs) for nonattainment area modeling use and for modeling emission rates for ozone precursors used to determine the ozone level impacts from emission of precursors such as nitrogen oxide. The implementation and permitting guidance was initially proposed by the Obama EPA in 2016.