Mill Creek Contamination Event Investigation Continues; Includes Public Health Assessment

Logos of responding entities


A multi-agency response team including Colorado Parks and Wildlife, Colorado Department of Public Health and Environment and the Town of Vail is continuing to investigate the source of a recent contamination event in Mill Creek that was discovered on Sept. 20 when citizens reported seeing dead fish downstream in Gore Creek near the International Bridge in Vail Village. No public health threat has been identified by the state toxicologist.

Staff from Colorado Parks and Wildlife, Town of Vail environmental sustainability, and Eagle River Water & Sanitation District have been documenting the impacts to aquatic life, which includes dead fish, algae and aquatic macroinvertebrates.

Colorado Parks and Wildlife has identified the most significant and apparent zone of impact as Mill Creek near Pirateship Park in Vail Village, downstream to the confluence with Gore Creek, and downstream on Gore Creek to the International Bridge.

Agencies including Colorado Parks and Wildlife, Eagle County Public Health and Environment, Eagle River Water and Sanitation District, Town of Vail, and CDPHE have joined together in working to collect fish, algae, aquatic macroinvertebrates and water chemistry samples in the affected stream segments to help identify the short-term and long-term impacts of the spill.

Colorado Parks & Wildlife employee in Mill Creek

A Colorado Parks & Wildlife employee checks the results from a BenthoTorch, which measures green algae, cyanobacteria, and diatoms, at the confluence of Mill Creek with Gore Creek on Friday, Sept. 24, 2021.

CDPHE Toxicologist Kristy Richardson says the state is disheartened to learn of the contamination event on Mill and Gore Creeks. “The contaminated water that contained a chemical algaecide is toxic to fish at high levels which is likely what led to the dead fish,” she said. “When diluted, the chemical is not very toxic for humans and mammals, so we don’t believe there was a public health threat, nor would there be an ongoing health threat.”

About 120 dead fish were collected from Gore Creek and upstream along Mill Creek on Sept. 21 as part of the investigation. Additionally, CPW staff has noted dead algae and aquatic macroinvertebrates within the significant zone of impact.

CDPHE implements the Clean Water Act in Colorado and regulates discharges, or waters and pollutants that entities release, to state waters in Colorado.

Nathan Moore, CDPHE compliance and enforcement section manager, said, “We are currently investigating the incident in coordination with local authorities and Colorado Parks and Wildlife to determine what violation of the state’s Water Quality Control Act may be associated with this occurrence and the responsible parties.”

For public health questions, contact Eagle County Public Health and Environment at 970-328-8755.

Public files related to Spill 2021-0460 are available on CDPHE’s website.