Facilities along Colorado’s Front Range with volatile organic compound (VOC) or nitrogen oxide (NOx) potential to emit (PTE) between 10 and 25 tons per year (tpy) may want to take a closer look at their permitting position now. If the Denver Metro/North Front Range (DMNFR) ozone nonattainment area is reclassified from Severe to Extreme, the major-source threshold for VOC and NOx would decrease from 25 to 10 tpy, potentially bringing additional facilities into major-source air permitting requirements.
An Extreme reclassification is not yet a certainty. The Denver Metro/North Front Range must demonstrate attainment of the 2008 8-hour ozone National Ambient Air Quality Standard (NAAQS) by July 20, 2027, based on monitoring data from the 2024 through 2026 ozone seasons. Preliminary data show several monitoring sites remain above the 75-parts-per-billion standard, increasing the possibility of a future Extreme reclassification. EPA would still need to complete the regulatory process before Extreme requirements would apply.
Facilities do not need to predict EPA’s final decision to begin planning. Reviewing PTE, existing permit limits, planned projects, and permitting options now can help identify potential exposure and preserve options if the major-source threshold changes.
Why Colorado’s 2027 Ozone Deadline Matters
The U.S. Environmental Protection Agency (EPA) evaluates attainment using a design value: the three-year average of the annual fourth-highest daily maximum 8-hour ozone concentration at each monitor. The 2027 deadline therefore rests on monitoring data from the 2024 through 2026 ozone seasons.
July 20, 2027, is the attainment demonstration deadline, not an automatic effective date for Extreme nonattainment requirements. EPA would still need to determine whether the area attained and take the applicable regulatory action before Extreme requirements would apply.
What the Latest Colorado Front Range Ozone Data Show
Ozone levels have improved modestly, but the region remains above the 2008 standard. EPA reported a preliminary 2022–2024 DMNFR ozone design value of 81 ppb and a 2023–2025 value of 79 ppb, still 4 ppb above the 75-ppb standard.
| Monitoring Period | Ozone Design Value | Relationship to 75-ppb Standard |
| 2022-2024 | 81 ppb | 6 ppb above |
| 2023-2025 | 79 ppb | 4 ppb above |
| 2024-2026 | Preliminary site-level values available | Final regulatory determination pending |
The change from 81 to 79 ppb is movement in the right direction, but it does not establish that the area will demonstrate attainment by the deadline. A 2026 Regional Air Quality Council presentation characterizes the long-term trend at the area’s highest monitoring sites as showing little reduction in ozone.
What Preliminary 2026 Colorado Ozone Data Show
The Colorado Air Pollution Control Division’s draft 2026 ozone summary, updated through August 26, 2026, shows preliminary 2024–2026 three-year averages above 75 ppb at several monitoring sites. The data are unvalidated, include values influenced by natural events, and may change.
The preliminary data do not establish that EPA will issue a failure-to-attain determination. They do indicate that, as of Colorado’s draft summary, the controlling three-year average remained above the 2008 standard.
Preliminary 2024–2026 Ozone Design Values in Colorado’s Denver Metro/North Front Range
What Extreme Ozone Nonattainment Could Mean for Colorado Facilities
An Extreme classification would affect more than the Denver Metro/North Front Range attainment schedule. For stationary sources, one of the most consequential changes would be a reduction in the major-source threshold for VOC and NOx from 25 tpy under the current Severe classification to 10 tpy under an Extreme classification. Because ozone is formed from precursor emissions, regulatory strategies focus on VOC and NOx.
Colorado experienced a similar expansion in major-source applicability when the area moved from Serious to Severe nonattainment in 2022. That change reduced the major-source threshold from 50 to 25 tpy causing additional facilities to be considered major sources invoking stricter permitting and Reasonably Available Control Technology requirements.
California’s Coachella Valley illustrates that an Extreme designation can drive broader State Implementation Plan requirements, including updated modeling, additional control measures, reasonable-progress demonstrations, and other planning obligations. Colorado’s future requirements would depend on its own SIP and EPA actions.
For Colorado facilities, the lower major-source PTE threshold could bring sources with VOC or NOx above 10 tpy into major-source applicability assessments. Depending on Colorado’s future SIP revisions and facility-specific circumstances, the implications could include Title V operating permit applicability, additional control-technology reviews, and changes to permitting requirements for new construction or facility modifications.
Extreme classification would also increase the Nonattainment New Source Review (NNSR) offset requirement. Projects that trigger major NNSR may need qualifying emission reductions to offset proposed emissions at a ratio of 1.5 tons reduced for each ton of new emissions. Emission Reduction Credits may be used to satisfy offset requirements when the reductions meet applicable federal and state requirements.
Facilities with VOC or NOx PTE between 10 and 25 tpy have the clearest immediate planning need. The most useful exercise now is not predicting EPA’s decision, but determining which facilities would be affected if the threshold moves from 25 to 10 tpy.
What Colorado Facilities Can Do Now
Extreme reclassification is not yet a requirement. However, the preliminary data and potential permitting consequences support early planning, especially for facilities with PTE between 10 and 25 tpy. A proactive review now can help facilities understand how a 10-tpy threshold could affect their permitting position and identify options before any new requirements take effect. Consider the following steps:
- Review VOC and NOx PTE. Screen each facility against both the current 25-tpy threshold and the potential 10-tpy Extreme threshold.
- Confirm the basis for PTE. Confirm whether operating hours, throughput, production, equipment, or emissions limits are enforceable and accurately reflected in current calculations.
- Identify facilities in the 10-to-25-tpy range. These facilities may be the most exposed to a future threshold change.
- Review planned projects. Engines, tanks, process equipment, production increases, and facility expansions can change PTE and affect future permitting options.
- Begin a permitting strategy review. Consider whether enforceable limits supporting synthetic minor status are feasible or whether preparation for major-source and Title V permitting is more practical.
- Monitor the validated 2024-2026 ozone design value data and EPA action. Preliminary monitoring data should inform planning, but facility decisions should account for the final regulatory process.
If the Denver Metro/North Front Range is reclassified as Extreme for the 2008 ozone standard, the major-source threshold for VOC and NOx would decrease from 25 to 10 tpy. Facilities between 10 and 25 tpy should review PTE, enforceable emissions limits, planned projects, and permitting strategies now so they understand how a lower threshold could affect them.
Additional Considerations for Colorado Oil and Gas Facilities
For upstream oil and gas facilities, additional strategies may help reduce PTE and preserve permitting flexibility if the major-source threshold changes. Colorado is already implementing NOx-reduction requirements for upstream oil and gas operations as part of its broader efforts to reduce ozone precursor emissions.
- Review general permit limits. Confirm current limits under applicable general permits. For example, GP07 for condensate loadout carries a 10-tpy VOC threshold. Where appropriate, transitioning to GP12 or a facility-wide construction permit may provide an opportunity to reduce PTE. For more background, see Trihydro’s Colorado General Permit 12 (GP12) for Oil & Gas Permitting Explained.
- Evaluate emission-reduction opportunities. Depending on the facility, options may include electrifying combustion sources, capturing routine or predictable emissions (ROPE), reducing flash emissions, or using a lease automatic custody transfer (LACT) system in place of truck loading. Facilities can also review engine sizing and opportunities to share heaters on separator vessels.
The key question is not whether a facility can predict EPA’s final decision. It is whether the facility understands how a 10-tpy threshold would affect its permitting position. Reviewing PTE, enforceable limits, planned projects, and permitting options now can clarify potential exposure and preserve time to develop an orderly strategy.
