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The Dallas Fort-Worth (DFW) Ozone Nonattainment Area (including Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, Tarrant, and Wise counties) and the Houston-Galveston-Brazoria (HGB) Ozone Nonattainment Area (including Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller counties) are expected to be reclassified to serious ozone nonattainment in early 2019. When DFW and HGB are reclassified as serious ozone nonattainment, any future projects that occur on or after the effective date of the reclassification will be required to use a Nonattainment New Source Review (NNSR) major source threshold of 50 tons per year (tpy) of nitrogen oxides (NOx) or volatile organic compounds (VOC). In addition, the applicability threshold for a Title V Operating Permit will be 50 tpy NOX or VOC.


The DFW area (including the previously listed counties with the exception of Wise County) and the HGB area were classified as serious and severe ozone nonattainment areas, respectively, due to the 1-hour ozone standard and 1997 8-hour ozone standard. Then, under the 2008 8-hour ozone standard, the DFW area (including Wise County) and the HGB area were designated moderate and marginal ozone nonattainment areas, respectively, effective July 20, 2012. However, despite the relaxation of the classifications for the DFW and HGB areas, both ozone nonattainment areas were required to conduct NNSR evaluations under the more stringent 1-hour and 1997 8-hour ozone standards due to anti-backsliding provisions.

On December 8, 2016, the 1-hour ozone and 1997 8-hour ozone National Ambient Air Quality Standard (NAAQS) redesignation substitute removed the anti-backsliding requirements, since a finding of attainment was made for the 1-hour ozone and the 1997 8-hour ozone NAAQS for DFW and for the 1997 8-hour ozone NAAQS for the HGB area. Due to the redesignation substitute, HGB was classified as a marginal ozone nonattainment area, and DFW was classified as a moderate ozone nonattainment area. The HGB classification was further revised to moderate ozone nonattainment on December 15, 2016. As such, for the past two years, both DFW and HGB air permitting projects were evaluated under the NNSR major source threshold of 100 tpy NOx or VOC and 100 tpy major source threshold for Title V.

Expected Reclassification

The attainment date for both DFW and HGB under the 2008 8-hour ozone NAAQS for moderate ozone nonattainment areas was July 20, 2018, based on the 2017 attainment year.1 Per TCEQ, the DFW and HGB areas did not demonstrate attainment by the deadline and are therefore, expected to be reclassified to serious. EPA has six months from the attainment deadline to publish a Federal Register notice with the proposed classifications. As such, it is anticipated EPA will publish the reclassification notification by January 20, 2019. The notice will then specify the effective date of the reclassification, which can be as soon as 30 days after publication or up to 60 days following publication.

After the effective date of the reclassification, new projects will be required to be evaluated against the ozone NNSR major source threshold of 50 tpy for NOx and VOC. In addition, the threshold for a Title V Operating Permit will be reduced to 50 tpy of NOx or VOC.

At this point, TCEQ has not published any specific information on the reclassification. However, TCEQ has started contacting sites that submitted a 2016 Emissions Inventory (EI) relaying the proposed reclassifications.

Trinity will provide an update as further news on the reclassifications are made available. If you have any questions regarding the ozone status for DFW or HGB, please contact the Dallas office at (972) 661-8100 or the Houston office at (713) 552-1371.


1 80 Federal Register No 44, March 6, 2015, Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan Requirements