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On August 23, 2019 the U.S. Environmental Protection Agency (EPA) took final action for the redesignation of 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, Waller counties) from moderate to serious for the 2008 ozone national ambient air quality standard (NAAQS). At the same time and in response to the redesignation, the Texas Commission on Environmental Quality (TCEQ) released its proposed Reasonable Available Control Technology (RACT) changes to 30 Texas Administrative Code (30 TAC) Chapter 115 Control of Air Pollution from Volatile Organic Compounds (VOC) and Chapter 117 Control of Nitrogen Compounds (NOX). As summarized below, the ozone redesignation coupled with the RACT proposals have implications on New Source Review (NSR) and Title V Operating Permit major source thresholds as well as control requirements.


The DFW and HGB ozone nonattainment areas have undergone numerous classifications over the years due to varying ozone standards and actual monitored ozone concentrations. This section provides a brief background on the classifications leading to the latest redesignation to “serious” for both areas.

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 Nonattainment New Source Review (NNSR) evaluations under the more stringent 1-hour and 1997 8-hour ozone standards due to anti-backsliding provisions.

On December 8, 2016, the anti-backsliding requirements were removed, 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; classifying DFW as moderate and HGB as marginal. Then HGB's classification was further revised to moderate ozone nonattainment on December 15, 2016. TCEQ adopted State Implementation Plan (SIP) Revisions for the attainment redesignation for the 1-hr and 1997 8-hour standard for the DFW and HGB areas in March 2019 and December 2018, respectively.

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. The DFW and HGB areas did not demonstrate attainment by the deadline and therefore, EPA published the reclassification from moderate to serious for both the DFW and HGB ozone nonattainment areas on August 23, 2019 with an effective date of the change September 23, 2019. With this change, Wise County (in the DFW nonattainment area) will for the first time be classified as serious.

NSR Permitting Implications

The redesignation to serious ozone nonattainment will reduce the major source threshold for NNSR Permitting and the Title V Operating Permits Program:

NSR Permitting:
  • Major Source = 50 tons per year (tpy) of VOC or NOX
  • Major Modification Significant Level = 25 tpy (please note, the steps allowed under the de minimis test for NNSR applicability change for serious ozone nonattainment areas. It is important to review the requirements of §116.150 when evaluating projects in the DFW or HGB areas)
  • Offset Ratios: 1.2: 1 in serious areas vs 1.15:1 in moderate areas
Title V Permitting:
  • Major Source = 50 tpy of VOC or NOX

RACT Proposal

Section 182(b)(2) of the Federal Clean Air Act requires SIP, for ozone nonattainment areas classified as moderate and worse, to include requirements for existing major sources of ozone precursor pollutants (VOC and NOX for ozone nonattainment areas) to apply RACT. Per 44 FR 53762, RACT is defined as “the lowest emission limitation that a particular source is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility”.

In conjunction with EPA's redesignation of the DFW and HGB areas to serious, TCEQ proposed changes to the VOC and NOX RACT rules. The below summarizes proposed revisions and is not inclusive of all revisions. TCEQ is also proposing nonsubstantive changes, including updating citation numbering. With Wise County now being classified as a serious ozone nonattainment area for the first time, the RACT proposals have the biggest implications for sources in Wise County as noted below.

  • Revisions to correct errors in emission limits applicable to surface coating miscellaneous metal parts and products and vehicle wipe-down solutions category (§115.421)
  • Wise County:
    • Increased control requirements for storage tanks
    • Increased inspection, repair, testing, and recordkeeping requirements
    • Deadline for RACT requirements to be implemented in Wise County is July 20, 2021
  • Removes language pulling Wise County requirements out separately and updates the DFW Area to be inclusive of Wise County (§117.10 Definitions)
  • Clarifies that operating hour restrictions under §117.410(f) do apply to stationary diesel and dual-fuel engines claiming exemption under §117.403(a)
  • Adds compliance flexibility for those required to perform testing under §117.8000 Wise County:
    • Process heaters and stationary internal combustion gas-fired engines will be subject to existing controls
    • An incinerator source category is being added
    • Reporting/recordkeeping/monitoring requirements added
    • Deadline for RACT requirements to be implemented in Wise County is July 20, 2021

Trinity will provide updates as additional information is provided by the TCEQ. If you have any questions regarding the redesignation, how to evaluate a project under the new permitting thresholds, or how RACT may apply to your facility, please contact the Dallas Office at (972) 661-8100