EPA Can Ignore ‘High-Wind’ Days When Judging Clean Air Compliance

Tenth Circuit upholds use of ‘exceptional events’ rule four days after D.C. Circuit does

The 10th Circuit Court of Appeals building in Denver, also known as the Byron White building.

For someone who lives on Colorado’s eastern plains, high winds might not seem to be an “exceptional event.” But for the purpose of determining compliance with the Clean Air Act, it is, according the federal government’s position that an appeals court just upheld. 

A Coloradan challenged the EPA’s use of the “exceptional events” rule when the agency determined that the State of Colorado satisfied federal air quality requirements. The town of Lamar had been classified as failing to meet the Clean Air Act’s standards for ambient air quality, and the state had been working to bring Lamar back up to standards. In 2016, the EPA approved Colorado’s air quality maintenance plan for Lamar, but in its assessment, the agency declined to account for 34 days where the area’s airborne dust spiked due to high winds. The EPA classified those windy days as exceptional events, but petitioner Robert Ukeiley claimed the agency abused its discretion in doing so.


On July 24, a 10th Circuit Court of Appeals panel sided with the EPA, saying that it used the exceptional events rule correctly by not counting the high-wind days against the state. The court denied Ukeiley’s petition for review under the Administrative Procedure Act. The EPA’s 10th Circuit victory comes days after the D.C. Circuit Court of Appeals upheld the EPA’s  interpretation of the exceptional events rule itself.

Under section 7619 of the Clean Air Act, the EPA can exclude exceptional events when judging whether a state complied with an air quality implementation plan. These include man-made occurrences that affect air quality but aren’t reasonably preventable or controllable and are unlikely to recur. But the 10th Circuit held that natural occurrences, like high winds, don’t have to be unlikely to recur in order to fit the statutory definition.

Lamar, a town of about 8,000 in southeastern Colorado, is susceptible to wind storms that kick up dust and soot particles that can be harmful to breathe. Lamar was designated in the early ’90s as a non-attainment area, or failing to meet the EPA’s National Ambient Air Quality Standards. After Colorado carried out a plan to rehabilitate Lamar’s air quality, the EPA re-designated Lamar to be in attainment in 2005. But the state’s obligations didn’t end there — Colorado had to submit another 10-year maintenance plan for Lamar in 2013 showing its compliance with the Clean Air Act. 

To be in compliance, an area can’t average more than one day of pollutant concentration over the limit over a three-year-period. In its submission, Colorado asked the EPA to ignore 55 days of pollutant-raising high-wind events that occurred between 2001 and 2015 — which by themselves constituted an average of 3.6 days a year exceeding the limits over that span. The state submitted meteorological data to support its argument that the air quality would have met the EPA standards on those days if not for the high winds.

Out of the 55 days Colorado pointed out, the EPA set aside 34 that it determined had met its criteria for high wind exceptional events. That was good enough for the EPA to approve Colorado’s proposed plan.

Ukeiley claimed the EPA acted arbitrarily and capriciously in giving the state leeway on the high wind days. He argued that high winds are common in Lamar, so they shouldn’t be counted as exceptional under the statute. 

But the court disagreed, rejecting what it called Ukeiley’s “personal interpretation” in favor of the statute’s definition of an exceptional event — one being “caused by human activity that is unlikely to recur at a particular location or a natural event.”

“The import of this difference is clear: Congress did not exclude recurring natural variations from its definition of ‘exceptional event,’” according to the opinion penned by 10th Circuit Chief Judge Timothy Tymkovitch. “We therefore disagree with Ukeiley’s interpretation of the statute and find the statute clear and unambiguous.”

Ukeiley, whom the court noted suffers from a lung condition made worse by air pollution, said in a statement that he was disappointed by the court’s decision.

“I think allowing wind in a place that it is so windy that there is a wind farm to qualify as an exceptional event and thus allow ignoring pollution level data will result in more dead and disease from air pollution,” he said.

The D.C. Circuit reached a similar outcome on July 20 in Natural Resources Defense Council, et al. v. EPA, et al. In that case, the NRDC and the Sierra Club challenged not an implementation of the exceptional events rule, but the EPA’s interpretation of the rule itself.

In 2016, the EPA adopted a definition of “natural events” to include those caused by a combination of both natural and human activity when the human activity doesn’t violate environmental regulations. The environmental groups said that new interpretation stretched the definition of natural events too far beyond its ordinary meaning. But the court sided with the EPA, finding its hybridized manmade-natural definition permissible under the Clean Air Act.

John Jacus, a partner at Davis Graham & Stubbs in Denver who regularly works with Clean Air Act issues, said the exceptional events rule is “exceedingly important” to states that are dealing with attainment vs. non-attainment designation. The 2016 rule change at the center of the D.C. Circuit case was a welcome one for states.

“Any states who are anxious for the ability to throw some outlier data out of their reporting on statistical grounds applauded the revisions to the rule,” Jacus said.

There’s a lot at stake for states like Colorado when it comes to the exceptional events rule. Having the EPA set aside days of pollution spikes can mean the difference between attainment and nonattainment. If the EPA finds an area in nonattainment, it can entail decades of maintenance obligations for the state, Jacus said.

Jacus, who isn’t involved in either the 10th Circuit or D.C. Circuit cases, said he wasn’t surprised at the result of Ukeiley v. EPA but was “a little surprised at the way they got there.” He noted that the D.C. Circuit at least went to step two of the Chevron deference analysis as that court found ambiguity in the Clean Air Act’s natural event’s definition for the EPA to clarify. The 10th Circuit spent little analysis in finding no such ambiguity.

But the two rulings show that the EPA’s use of the exceptional events rule isn’t very vulnerable right now, Jacus said. “I think courts are likely to be somewhat deferential to EPA and say this is reasonable, even if it doesn’t meet with everyone’s approval.”

— Doug Chartier

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