Suncor Energy refinery violated pollution permits for 900+ hours during three-month shutdown in Commerce City; environmental group 350 Colorado reports excessive emissions of sulfur dioxide, hydrogen sulfide, carbon monoxide and particulates

June 7, 2025 (The Denver Post) –

Suncor Energy’s oil refinery in Commerce City exceeded its permitted pollution limits for more than 900 cumulative hours during its three-month shutdown in late 2022 and early 2023, according to a study by an environmental group — and Colorado regulators say they are investigating potential violations during that incident.

350 Colorado, an environmental group that advocates for the elimination of fossil fuels, says in its recently released report that it reviewed Suncor’s self-reported documents connected to the shutdown and determined there was a notable increase in the frequency of permit violations while the refinery was offline.

During that time, the plant released excessive amounts of sulfur dioxide, hydrogen sulfide, carbon monoxide and particulate matter such as soot, according to the report titled “Suncor’s Commerce City Refinery : Looking Back to Plan Ahead.”

The report counted each hour during which at least one of those regulated toxics was emitted. So if all four were released during the same hour, 350 Colorado counted that as four hours of permit violations.

At the time, people who live in neighborhoods surrounding the refinery hoped that the shutdown would result in cleaner air,

but no one had looked into the data, said Heidi Leath , a climate policy analyst with 350 Colorado.

“They just thought they were going to get a break from the pollution,” she said. “We were really curious to see if the air quality would improve.”

The 350 Colorado report also looked at the three-month closure’s impact on gas prices and determined that although gas prices spiked at the time, the refinery does not help Colorado maintain lower gas prices.

Efforts to reach Suncor officials for this story were unsuccessful.

On Dec. 21, 2022 , the Suncor refinery’s hydrogen plant malfunctioned during an extreme deep freeze, during which the temperature in Denver dropped 37 degrees in an hour, eventually plunging to minus 24 degrees. When the hydrogen plant tripped, it caused a cascade of problems for Suncor’s machinery, leading the company to shut down operations for three months to make repairs.

Suncor refines about 98,000 barrels of crude oil per day during normal operations and supplies about 40% of the gasoline used in Colorado . The state’s only refinery also produces diesel, jet fuel and liquid asphalt.

As for the pollution during the shutdown, refineries often release more chemicals during a malfunction as they race to stop production without creating a safety hazard, such as an explosion from accumulating fumes. They also tend to release more toxics when they restart production and calibrate their instruments.

But excessive emissions from those situations often are exempt from regulation, Leath said.

“They basically give a free pass, and they allow emissions to go up during these periods and put people’s health at risk,” she said of state regulators.

That hasn’t stopped the Colorado Department of Public Health and Environment from opening an investigation into potential violations during the 2022-23 shutdown.

In January, the agency sent Suncor a compliance advisory, which is the first step in an investigation into permit violations, said Kate Malloy , a spokeswoman for the department’s Air Pollution Control Division.

That compliance advisory covers alleged violations that occurred between July 1, 2022 , and June 30, 2023 , including the shutdown and restart period from the deep freeze.

The agency will be looking into Suncor for exceeding its emissions limits for air pollutants, failing to meet required operating parameters and failing to follow required procedures for operating and maintaining equipment, according to the 57-page advisory.

In July, the state health department and the Environmental Protection Agency served a notice of violation to the refinery, the first step in an enforcement action after both agencies discovered violations during inspections between 2020 and 2023. That notice is still pending.

Government investigations into environmental violations can take years, and they also allow companies to negotiate penalties.

In February 2024 , the state hit Suncor with a $10.5 million penalty, the largest in Colorado history for air permit violations. That fine was for excessive pollution between July 2019 and June 2021 .

A $9 million fine announced in 2020 covered multiple air pollution violations since 2017.

As for gas prices and their connection to Suncor’s operation in Commerce City , they rose dramatically during the shutdown — 51% in Colorado . Drivers paid as much as $4.10 per gallon during the winter months after the malfunction. Winter gasoline prices are typically cheaper because of lower demand.

But 350 Colorado argues in its report that Suncor’s presence does not benefit Colorado drivers overall when it comes to the price they pay at the pump. The study found that over the past five years, Colorado has seen higher gas prices than 85% of the states without refineries and higher prices than 79% of the states with them.

“Everybody said gas prices would rise, and they did in the short term,” Leath said. “But would it really be true that we would have higher gas prices in Colorado if we didn’t have the Suncor refinery ? To our surprise, honestly, most of the states that don’t have refineries have lower gas prices.”

Grier Bailey , executive director of the Colorado Wyoming Petroleum Marketers Association , which represents gas retailers, was highly critical of the 350 Colorado report.

“In summary, it seems clear the entire ‘report’ relative to gas prices is a hit piece designed to assuage a policy audience that there won’t be any impact on fuel prices if far-left fringe groups like 350 get their way,” Bailey said. “That is simply not something that is responsible to assert.”

Bailey said the comparison between average gas prices in Colorado and other states did not take into account things such as taxes and other fees that Colorado places on suppliers and distributors, which eventually end up in the prices consumers pay. Those additional taxes and fees amount to about 30 cents per gallon and are slated to rise in the coming years.

He warned that it would be a mistake to close the Suncor refinery because people still would need all the products it supplies, meaning fuel would be delivered via pipeline, rail or trucks, which would increase emissions from pipeline terminals, place more trucks on the roads and put an additional cost burden on consumers to pay for the transportation to get fuel delivered.

Finally, it was unfair for the report to fail to acknowledge the extraordinary steps the oil and gas industry, Gov. Jared Polis and others took to keep the state supplied with fuel during the shutdown, Bailey said. He accused 350 Colorado of omitting key points to bolster its position that Suncor should be closed.

“Trying to dress up a policy position paper as a ‘study’ doesn’t impress serious people who are trying to keep Colorado’s economy moving,” he said.

nphillips@denverpost.com