A U.S. Court of Appeals for the DC Circuit Tuesday upheld the U.S. Environmental Protection Agency’s (EPA) decision not to designate the Uinta Basin in Utah as a nonattainment area for ozone.The Western Energy Alliance (WEA), which was in a rare alignment with EPA on the case, applauded the decision.

WEA said industry and government efforts — including those by EPA — have mitigated a past winter ozone problem in the Uinta to the point that there has not been a high level reading in the basin since late 2013.

WEA supported the EPA as a defender/intervenor in the case, dubbed “Mississippi Commission on Environmental Quality v. EPA,” opposing the WildEarth Guardians and other environmental groups that brought the action alleging that the agency failed to meet federal Clean Air Act (CAA) standards.

The DC Circuit decision rejected the petitioners’ arguments that EPA had “acted arbitrarily and capriciously,” instead deciding that the agency complied with the Constitution and “wholly satisfied — indeed, in most instances, surpassed — its obligation to engage in reasoned decision-making.”

The consolidated petitions from the various environmental groups were all centered on EPA’s actions under CAA requiring that it set National Ambient Air Quality Standards (NAAQS) for six pollutants that are considered possible threats to public health and welfare. Once NAAQS is established, EPA then designates each area in the United States as either in attainment or nonattainment.

EPA can designate an area as “unclassifiable” if the data it has is insufficient to allow a determination. That is the designation that EPA gave the Uinta because it did not have three consecutive years of data on which to base an attainment/nonattainment determination. There was a catch, however, in the fact that private companies’ monitoring for 2009-2011 was available, and it showed levels significantly exceeding the 2008 NAAQS for ozone.

Nevertheless, EPA found that the private data was insufficient, and WildEarth and other groups challenged the agency’s conclusion that the Uinta Basin is unclassifiable rather than a nonattainment area.

“WildEarth Guardians and the co-plaintiffs attempted to force EPA to make an ozone nonattainment designation based on monitoring data that did not meet the Clean Air Act standards,” said Kathleen Sgamma, WEA vice president for government and public affairs. She said she believes WEA’s intervention in the case was “instrumental” in helping Utah and various county officials convince the appeals court that EPA had followed CAA procedures.

“In sum, the EPA reasonably declined to rely on data that it considered of insufficient quality for designation purposes,” the DC Circuit ruling says. “With that conclusion, and having reviewed the remainder of WildEarth’s challenges and determined that they lack merit, we deny the group’s petition for review.”

WEA points out that much work among industry, federal, state and tribal representatives has been ongoing since winter 2010 when elevated ozone levels were first recorded in the Uinta. It was an academic study involving the National Oceanic and Atmospheric Administration that brought focus to the issue of winter ozone. Before that, the problem was viewed as occurring mostly in summertime.

“As a result, Utah has documented reduced air emissions in the Uinta Basin and there has not been a high ozone reading since December of 2013,” WEA said.