EPA Proposes Severe Ozone Nonattainment Status for the Denver Metro/North Front Range Region – What Does it Mean for You?

In a move that has been expected for some time, on April 13, 2022, the U.S. Environmental Protection Agency (EPA) proposed to redesignate 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 EPA included redesignations for several other parts of the U.S. in the same notice. 


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 - 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.

EPA’s proposed rule starts a 60-day public comment period (ending June 13, 2022) where any party can submit information regarding the proposal. Following receipt of public comments, EPA must evaluate and develop responses to the comments before publishing a final rule. It takes EPA at least two to six months to reach the final rule stage, meaning the final redesignation is not likely before August, and may not happen until late 2022 (or potentially early 2023).

What does this mean for my operations?

Although nothing formally changes until EPA finalizes the redesignation, there are steps you may consider in the near-term to get ready.

  • The change will only affect facilities located within the designated ozone nonattainment area. If there is any question, CDPHE’s air quality map can help you verify your facility’s location relative to the relevant boundaries. The severe designation will not apply to the portion of northern Weld County that EPA recently recognized to be included in the ozone nonattainment area, since that change was specific to the 2015 ozone NAAQS (the 70 ppb standard).
  • The severe designation will result in a requirement that only “reformulated gasoline” be sold within the nonattainment area starting one year following finalization. As a result, relative gasoline prices will increase.
  • The Title V operating permit major source thresholds for NOx and VOCs will be reduced from the current 50 tons per year to 25 tons per year. Under a severe nonattainment designation, existing facilities with potential NOx or VOC emissions of 25 or more tons per year and less than 50 tons per year may be required to obtain a Title V operating permit. CDPHE estimates there are currently 470 facilities in this emission range.
    • Potentially 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 their NOx or VOC emissions to less than 25 tons per year, making them a “synthetic minor” source. Permit modifications should be complete within one year after the final redesignation date.
    • Facilities required to obtain a Title V operating permit will need to submit a Title V operating permit application that can be deemed administratively complete within one year after the final redesignation date.
  • Major source air permitting thresholds in the nonattainment area will similarly fall to 25 tons per year of NOx or VOCs. New projects or facility modifications may trigger nonattainment New Source Review permitting, requiring significantly 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.
  • Additional CDPHE air regulatory changes may be required to move the nonattainment area into projected NAAQS compliance. The EPA requires states to establish State Implementation Plans (SIPs) demonstrating NAAQS compliance by a future date. SIPs are developed by relevant planning agencies. For the DMNFR, the Regional Air Quality Commission (RAQC) and the North Front Range Metropolitan Planning Organization (NFRMPO) are the planning agencies charged with developing the SIP. The RAQC and NFRMPO will work collaboratively with CDPHE to establish plans, including potential regulatory changes, necessary to model future NAAQS compliance. Complicating this effort will be the parallel requirement to ultimately achieve the lower 2015 ozone NAAQS.

Interested in commenting on the proposed rule?

EPA is holding a virtual public hearing on May 9, 2022, where interested parties can learn more and make oral comments. Written comments can be submitted through the Federal eRulemaking Portal, email, fax, mail, and hand delivery until June 13, 2022—remember to identify any written comments with the appropriate docket number: Docket ID No. EPA–HQ– OAR–2021–0741.

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

Our team of air quality professionals remains current on the latest regulations and has decades of experience assisting facility owner and operators with compliance, permit modifications, and operational changes. Drop us a note if you would like to discuss how the severe nonattainment designation will affect your operations. 

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Jay Christopher
Senior Scientist Specialist, Englewood, CO

Jay has over 40 years of environmental experience. Since 1990, he has specialized in air quality issues and permitting programs affecting a broad range of facility operations, with hands-on experience in both corporate headquarters and facility regulatory settings, as well as in the environmental consulting world. Jay has managed the environmental compliance program and environmental professional staff for a major refinery’s downstream businesses and is involved in regional air quality issues and national trade groups.
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