The Suncor Energy refinery in Commerce City spilled too much cyanide into Sand Creek last month, according to a notification from the company.
The excessive amount of cyanide was discovered during routine testing on Feb. 25, the company reported on Wednesday evening. The test found cyanide levels above 20 parts per billion, above the permitted level of 17 parts per billion.
A water sample tested two days later found the refinery was back in compliance with its water pollution permit. The notification was sent via phone calls, text messages and emails to those who have enrolled in the refinery’s alert system.
The spill is under investigation by the Colorado Department of Public Health and Environment.
The cyanide was released into Sand Creek via Outfall 20, a pipe that is the main wastewater discharge point for the refinery. That pipe pours 3.5 million gallons of water per day into Sand Creek, a tributary to the Platte River — a source of drinking water for residents and irrigation for farmers in northern Colorado and Nebraska.
Suncor is permitted to release specific levels of chemicals, including benzene, arsenic and polyfluoroalkyl substances — also known as PFAS, or “forever chemicals — through its water pollution permit.
Cyanide is extremely toxic to humans and can cause cardiovascular and respiratory problems as well as irritation to eyes and skin. The Environmental Protection Agency’s standard for cyanide in drinking water is 200 parts per billion.
Get more Colorado news by signing up for our Mile High Roundup email newsletter.