On October 7, 2022, the U.S. Environmental Protection Agency (EPA) finalized a rule that redesignates the Denver Metro/North Front Range (DMNFR) ozone nonattainment area from “serious” to “severe” for the 2008 ozone National Ambient Air Quality Standard (NAAQS). The rule goes into effect on November 7, 2022, triggering a one-year countdown clock for affected facilities to assess and confirm compliance.

Background on nonattainment areas and the 2008 NAAQS for ozone

EPA establishes NAAQS for several air pollutants, including ozone. Ozone is not directly emitted by most sources, but is formed near ground level as a result of a chemical reaction between nitrogen oxides (NOx), volatile organic compounds (VOCs), and sunlight. Hence, NOx and VOCs are the relevant regulated air pollutants. Areas where air quality does not meet specified standards become nonattainment areas and are designated as marginal, moderate, serious, severe, or extreme.

The 2008 NAAQS for ozone is 75 parts per billion (ppb), and the formula for determining the DMNFR’s average is based on actual monitored values from certified air quality monitoring stations located throughout the region for the years 2018 through 2020. The formal determination data is complex, but the calculated values were significantly higher than the standard (as is the 2021 data). The affected area can be seen on the Colorado Department of Public Health and Environment’s (CDPHE’s) air quality map after clicking the “O3 8-yr NAA (2008 NAAQS)” check box.

What's in the final rule?

The final rule closely mirrors the proposed rule EPA released in April 2022. The following provides a summary of key changes, and we have highlighted some important aspects that should be considered.

• The change only affects facilities located within the DMNFR ozone nonattainment area for the 2008 standard. CDPHE’s air quality map can help you verify your facility’s location relative to the relevant boundaries. The severe designation does not apply to portions of northern Weld County, which is only affected by a new  “moderate” nonattainment designation based on the 2015 ozone NAAQS (the 70 ppb standard).
  
• The Title V operating permit major source thresholds for NOx and VOCs are reduced from the current 50 tons per year to 25 tons per year. Under the severe nonattainment designation, existing facilities with potential NOx or VOC emissions of 25 or more tons per year (as opposed to the prior 50 tons per year threshold) may be required to obtain a Title V operating permit unless they take other steps to reduce potential to emit. When determining emissions thresholds, the CDPHE requires that insignificant sources be included in analyses. CDPHE estimates more than 450 facilities may now be classified as major sources as a result of this change.
  • Affected facilities may be able to modify their existing air permit by committing to additional emission controls, limiting hours of operation, or other measures that limit NOx or VOC emissions to fewer than 25 tons per year, making them a “synthetic minor” source. Permit modifications must be complete by November 7, 2023.
  • Facilities required to obtain a Title V operating permit need to submit a Title V operating permit application that can be deemed administratively complete by November 7, 2023.
• Major source air permitting thresholds in the nonattainment area are similarly reduced to 25 tons per year of NOx or VOCs. New projects or facility modifications may trigger Nonattainment New Source Review permitting, requiring more complex permit applications. In particular, impacted projects in the nonattainment area will need to meet a higher emission control standard, referred to as Lowest Achievable Emission Rate (LAER), which is generally the lowest emissions rate currently achieved for the same source type anywhere in the U.S. In addition, emission increases of NOx or VOCs will typically require emission offsets of 1.3 to 1 tons per year.
  • As part of the process for permitting new sources or modifications to existing sources, CDPHE has recently changed guidance and procedures regarding emissions modeling. The new approach is more conservative and may result in additional steps and time to obtain air permits in Colorado.
• The Regional Air Quality Commission (RAQC) and the North Front Range Metropolitan Planning Organization (NFRMPO) have finalized the proposed State Implementation Plan (SIP), which will be heard by the Colorado Air Quality Control Commission in December 2022 before going to legislature in early 2023.
  

Want to learn more or discuss how this news affects your facility? Contact us!

Trihydro’s air quality professionals remain current on the latest regulations and have decades of experience assisting facility owners and operators with compliance, permit modifications, and operational changes. Connect with us if you would like to discuss how the severe nonattainment designation affects your operations.