The Colorado Department of Public Health and Environment told Suncor in a letter last week that it expected to meet with the energy company prior to restarting the piece of machinery that caused a cloud of yellow vapor at the Commerce City refinery on March 17.

“As discussed throughout the last year, the Division is concerned about the number, duration, and nature of excess emissions events at Suncor,” wrote Shannon McMillan, the manager of compliance and enforcement for the Air Pollution Control Division. McMillan added that the fluidized catalytic cracking unit that caused the excessive emissions was also behind a similar episode in December 2019. 

“The Division expects Suncor to complete a detailed, thorough investigation into the cause of the issue(s) that resulted in the excess emissions as well as the identification and completion (as appropriate) of the steps necessary to prevent a recurrence,” the letter continued.

At the time of the yellow emissions cloud, CDPHE said that there appeared to be no ongoing risk to the community. On March 26, Suncor announced that it had completed maintenance on Plant 2, which contained the malfunctioning equipment. However, the unit that caused the cloud “will remain offline until we have completed our thorough investigation of the air blower trip that occurred on March 17.”

Separately, CDPHE issued a memorandum in response to the U.S. Environmental Protection Agency’s suspension of enforcement during the COVID-19 pandemic. “The regulatory requirements remain in place and must be followed,” the department advised.