Colorado Legislative Committee Tackles Ozone Air Quality Policy Questions

Brownstein Hyatt Farber Schreck

Brownstein Hyatt Farber Schreck

On Aug. 25, Colorado’s Legislative Interim Committee on Ozone Air Quality convened for its first of five planned meetings, primarily to discuss background information on Colorado’s ozone air quality issues. As defined by statute in HB 23-1294, the committee’s purpose is to study ozone and air quality and the factors that contribute to them, analyze strategies to improve ground-level ozone levels and developing policies to improve ozone. The committee is specifically focused on ozone, unlike the much broader mandate of the state’s Air Quality Control Commission (AQCC).

Below is a summary of what the committee discussed in its first meeting and where they will go from here.


Ozone formation is a complex and difficult-to-predict science—a fact stressed by representatives from the Colorado Department of Public Health and Environment (CDPHE) and its Air Pollution Control Division (APCD). Colorado’s background ozone levels, which the state has tracked since 2000, account for the majority of the state’s total ozone measurements. This means that Colorado can only control about 30% of the ozone measurements we record.

The Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) to regulate air quality, including ozone levels. Compliance with these standards is determined based on the three-year average of the fourth maximum daily eight-hour average ozone levels. Due to the variability of ozone concentrations caused by weather, meeting NAAQS can be a uniquely confounding challenge.

Although air quality and ozone levels in the Denver Metro/North Front Range area have improved greatly over the past several decades, the area has continued to face federal ozone nonattainment issues. Initially classified by EPA in 2012 as a marginal nonattainment area for the 2008 ozone standard (75 parts per billion), the area was reclassified as moderate in 2016, serious in 2020 and severe in 2022. The classifications are marginal, moderate, serious, severe and extreme. For the 2015 ozone standard (70 parts per billion), the area was initially classified by EPA in 2018 as marginal and reclassified as moderate in 2022. The area is subject to both standards because, as the result of litigation, revocation of the 2008 ozone standard was not included in the final rule implementing the 2015 ozone standard.

Because of this, Colorado is mandated to develop State Implementation Plans (SIPs) to achieve attainment to both ozone standards, which allow for local and regional planning with federal oversight. Although attaining NAAQS is crucial, even small reductions in ozone levels matter. The Air Quality Control Commission (AQCC) is scheduled to hold a hearing on the 2008 ozone standard SIP in December 2023, while work on the 2015 ozone standard SIP is underway and expected to be proposed to the AQCC in 2025.

Where We Go From Here:

Gov. Jared Polis also issued a directive in March 2023 to achieve a 30% reduction in NOx emissions from the oil and gas sector in the nonattainment area by 2025 and a 50% reduction by 2030. Regulatory efforts of the state’s Energy and Carbon Management Commission (ECMC)—formerly, the Colorado Oil and Gas Conservation Commission, which is housed within the Colorado Department of Natural Resources (DNR)—and CDPHE are underway, involving rulemaking and stakeholder processes to meet these targets.

A lot of pressure is focused on oil and gas. During the committee meeting, Earthjustice leveled particular criticism at the state permitting process for oil and gas operations. During public comment, half of the comments came from members of environmental groups who advocated for stricter controls on oil and gas operations, including permit denials and mandatory well plugging for low-producing wells. The other half of the comments were more focused on source contribution and looking beyond further oil and gas regulation to reach attainment. Transportation and lawn care were two sectors where members of the public are interested in seeing more regulation. Several committee members also voiced concerns that the focus on oil and gas was myopic, unsupported by data, and would not actually reach attainment as fast as a cross-sector approach.

When the committee meets next on Sept. 22, they will likely focus on ozone sources, data and impact. Oil and gas industry members are expected to be invited to give a presentation during subsequent meetings, along with local governments. The committee also signaled that CDPHE, APCD, DNR and ECMC will be invited back to later meetings, in which the committee will begin to workshop legislative solutions that fit each agency’s capacity and processes—potentially even compiled in a single bill.

DISCLAIMER: Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations.

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