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State leaders recommend creating three new nonattainment areas in Utah that fall short of Environmental Protection Agency standards for ozone pollution, even as Utah waits to hear from the feds on the status of its small-particulate pollution.

Salt Lake and Davis counties, as well as portions of Weber, Utah, Duchesne and Uintah counties, don't meet new federal standards for ozone pollution, according to an analysis from the Utah Department of Environmental Quality. Gov. Gary Herbert has proposed that the EPA designate three nonattainment areas in Utah, two of them along the Wasatch Front.

One comprises the western side of Utah County; another combines Salt Lake and Davis counties, as well as the western side of Weber County and a more populated portion of Tooele County; and the third encompasses areas in Duchesne and Uintah counties with an elevation below 6,000 feet.

Unlike many pollutants, ozone is not emitted directly into the atmosphere but is formed when sunlight reacts with other chemicals in the air, primarily nitrogen oxide and a group of pollutants known as volatile organic compounds. This means ozone is typically a summertime concern — as it is on the Wasatch Front.

Population centers on the Wasatch Front continue to exceed the EPA's 2015 standard of 70 parts per billion despite an overall downward trend, according to the DEQ analysis. At the Hawthorne monitoring station in Salt Lake City, the three-year average used to determine ozone attainment status is sitting at 76 parts per billion. In Bountiful, that same average is currently 72; northern Provo and Ogden also are averaging 72.

Compliance with the EPA's eight-hour ozone standard is determined by taking the four highest ozone levels recorded in a given area, discarding the top three, and then averaging the fourth-highest values across three years.

Bryce Bird, director of the Utah Division of Air Quality, said the DEQ decided to split Utah County from its northern neighbors because its transportation planning is governed by a different entity in Salt Lake, Davis and Weber counties.

Homes and vehicles are the largest sources of ozone precursors in these areas, Bird said. In Salt Lake, vehicles alone are responsible for nearly half the county's emissions of nitrogen oxide.

Populous areas in Tooele County were included in the Salt Lake nonattainment area because of the large number of residents who commute from that county to Salt Lake for work, contributing to emissions of nitrogen oxide. The DEQ does not have three years' worth of data regarding ozone levels in Tooele County and was unable to determine the area's compliance with the 2015 ozone standard.

Data collected in 2013 and 2014 put ozone levels in Tooele County in the range of 69 and 72 parts per billion, respectively. In 2015, after the DEQ moved its monitoring station to a more central location in the Tooele Valley, ozone levels were measuring 71 parts per billion.

The situation in Uintah and Duchesne counties is more unusual. There, ozone has been observed spiking in the winter, particularly when there is snow on the ground and an atmospheric temperature inversion in place.

Precursor pollutants are believed to originate from the oil and gas industry, Bird said.

Ozone levels in Roosevelt in Duchesne measured 75 parts per billion between 2013 and 2015, according to the DEQ analysis, and 79 parts per billion in Ouray in Uintah County.

Bird said he anticipated that all three of the recommended nonattainment areas would be classified as marginal nonattainment areas. That would mean Utah would have a three-year period to monitor ozone trends to see if pollution controls already in place manage to bring the areas into compliance. If after three years Utah continued to struggle with the new standard, the areas would be reclassified as moderate nonattainment areas, and the state would be required to submit to the EPA a plan for reducing ozone pollution.

But it's unclear exactly how these three nonattainment areas should be classified, because the EPA has not yet released its criteria for classifying the severity of nonattainment areas under the new standard. Bird said he anticipates that the EPA will release that criteria before year's end.

The EPA has until October 1, 2017, to review the state's recommended nonattainment areas for ozone and issue a final decision on each area.

Meanwhile, Bird said, the state is still waiting to hear back from the EPA regarding the status of the state's current nonattainment areas for small-particulate pollution, known as PM 2.5.

Salt Lake City, Provo and Logan all missed a Dec. 31, 2015, deadline for achieving compliance with the EPA's PM 2.5 standard — which, under the Clean Air Act, triggers a series of steps, beginning with the EPA's reclassification of the nonattainment area as a "serious" nonattainment area.

When it became evident in fall 2015 that Utah would not make the end-of-year PM 2.5 deadline, the EPA proposed to reclassify Utah's nonattainment areas early, in exchange for granting the state more time to draft a new implementation plan.

However, the EPA "was unable to finalize its November proposal" and has yet to declare Utah's new PM 2.5 status, according to agency spokeswoman Lisa McClain-Vanderpool.

Utah areas that did not meet the Dec. 31 deadline will be reclassified as serious when the EPA issues its final determinations of attainment, she said.

Bird said he expects those final determinations to be issued before year's end. But two environmental groups have already filed suit against the EPA for its failure to issue those determinations by the July 1 deadline set forth in the Clean Air Act.

Meanwhile, Bird said, Utah regulators have already started working on the new, stricter state implementation plan that would be required under the new classification.

"All the technical work is really well along," he said.

The reclassification process could be more complicated for Cache County, Bird said, because Utah originally intended to file for a one-year extension of the Dec. 31, 2015 deadline. At the time, he said, it appeared as though compliance were imminent — the Logan nonattainment area needed one more year without violating the PM 2.5 standard to declare attainment.

But during a severe inversion episode in early 2016, Cache County violated the PM 2.5 standard seven times, Bird said, prompting Utah to leave its application for an extension unfinished.

"Another year would have just shown that we were over the standard," Bird said, "which we already knew by then."

Because the state had anticipated compliance in the Logan area by 2015, the EPA will probably reject the state's implementation plan for that area, Bird said. That action, he said, will make the road to a new Cache County plan a little longer, and could open up the state to federal sanctions.

But Bird said he thought it unlikely that any sanctions would actually come into play. The state plans to have new implementation plans in place in a little over a year.

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