Colorado air regulators have grossly underestimated ozone pollution from some oil and gas operations due to a data error

Colorado’s air regulators on Friday withdrew large parts of a draft plan to reduce ozone pollution, acknowledging that emissions from some oil and gas drilling and hydraulic fracking operations had been underestimated.

The approval, detailed in a memo to state air regulators, sends regulators back to the drawing board as they try to bring Front Range air quality into line with federal health standards.

It also invites a new scrutiny of the state’s oil and gas industry, which the state already recognized as the largest source of local ozone constituents in the region – even before they acknowledged the recent data error.

Environmental groups praised the recent decision. After criticizing an initial ozone plan released in June, they now see an opportunity to push for new air quality regulations, including rules limiting fracking operations during the summer ozone season or demanding cleaner electric drilling rigs.

“They don’t try to cover up their mistakes, but stand by them and recognize that some tough decisions need to be made,” said Jeremy Nichols, the climate program director for WildEarth Guardians, an environmental advocacy group.

Colorado’s air regulators are now planning to rewrite large portions of the state’s ozone plan before submitting it to federal regulators next year. Lorena Gonzalez, who leads the climate campaign at Conservation Colorado, said the move was appropriate given an “ozone crisis” in the Front Range.

“Chronic levels of ozone are putting the public at risk, so it’s really time we figured out this situation,” Gonzalez said.

Colorado is scrambling to revise its air quality regulations after repeated failures to bring the Front Range’s ozone pollution below federal health standards.

The pollutant is a well-studied lung irritant that has been linked to many health problems, including asthma, low birth weight and premature death.

Ground-level ozone is not normally emitted directly into the atmosphere from exhaust pipes and smokestacks. It comes from a number of sources – automobiles, factories, wildfires, oil and gas operations – that emit nitrogen dioxide and hydrocarbons into the air. These “primary pollutants” react in the atmosphere amid heat and sunlight to produce ozone.

In the Front Range, most ozone pollution comes from “background” pollution outside of the state, but local sources are responsible for levels exceeding federal health standards. Estimates in the state’s latest ozone plan show that the oil and gas industry is the single largest source of local ozone constituents, followed by automobiles and other vehicles.

The federal government has asked the state to take immediate action. In September, the US Environmental Protection Agency classified a nine-county area stretching from Fort Collins to Castle Rock as “severe” ozone depleting, below its health standard of 75 parts per billion. The agency also maintains a 70 parts per billion standard, which it adopted in 2015 to address growing concerns among medical experts about ozone pollution. It called the region a “moderate” violator under the tougher threshold.

A plan to bring the region into line fell to the Regional Air Quality Council, the premier air quality planning agency in the Denver metropolitan area. She released a draft of the plan in August before submitting it to the Colorado Air Pollution Control Division.

Kevin J. Beaty/Denverite
A hazy view of Denver from Lookout Mountain. September 14, 2022.

These state regulators have now identified an error in the data underlying the draft.

The plan included emission estimates from oil and gas pre-production operations such as drilling, hydraulic fracturing and well venting.

Matt Sura, an environmental attorney currently working with Conservation Colorado, said he began questioning the math behind those estimates while reviewing a plan to drill new wells in Weld County. PDC Energy, the company behind the plan, presented data showing that the pre-production process for each new well would emit almost twice the amount of nitrogen dioxide than estimates included in the state’s ozone plan, Sura said.

Sura brought the discrepancy to the attention of state aviation regulators.

In its note explaining its calculation error, the Air Quality Control Division noted that the plan relied on industry data from 2017, which explained the large gap in emissions estimates. After recalculating with the new numbers, estimates for ozone-causing emissions from all of the pilot holes shot up dramatically. Estimates for a class of air pollutants known as volatile organic compounds rose from 7 tons to 8 tons – an 11 percent increase. Estimates for nitrogen dioxide release rose from 17 tons to 33 tons – a jump of 96 percent.

The Colorado Air Quality Control Commission was due to vote on the ozone plans next month. Because of the miscalculation, the department told commissioners it would withdraw large parts of the plan to meet the EPA’s more relaxed 75 parts per billion standard and would reconsider any new regulations next year.

Lynn Granger, executive director of the American Petroleum Institute of Colorado, said what appears to be an “unintentional mistake” will not stop the state’s oil and gas companies from continuing to improve their operations and reduce their overall impact on air quality.

“Our industry remains committed to meeting the goals set out in the state’s greenhouse gas roadmap, and we look forward to continuing our collaboration with state agencies and other stakeholders as we pursue our shared goals,” said Granger

To the disappointment of some environmental groups, the department still plans to proceed with a separate plan to bring ozone levels up to the stricter standard of 70 parts per billion, although regulators have already acknowledged that’s not enough to meet the threshold of up to one Federal deadline of 2024.

Regional Air Quality Council director Mike Silverstein has said there is no chance the Front Range will meet the deadline and submitting the inadequate plan is a strategy to buy more time. Once the EPA downgrades the region from a “moderate” to a “serious” violator under the stricter standard, the region has until 2026 to meet the stricter standard. Because the looser standard has the same deadline, the region can align itself with a four-year plan to reduce ozone emissions.

Environmental groups have criticized the strategy as both cynical and illogical. Nichols, the attorney for WildEarth Guardians, said the state should instead come up with a plan that has a reasonable chance of complying with federal law.

“They’re basically saying, ‘We’ve already concluded that the plan will fail, so we’re just not going to look at it, even though the emissions estimates are wrong,'” Nichols said. “We have argued that they cannot legally adopt a plan that is going to fail.”

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