VAIL — An investigation into the source of a recent contamination spill in Mill Creek is still underway, according to a joint announcement released Tuesday, Sept. 28, by Colorado Parks and Wildlife, Eagle County Public Health and Environment, Eagle River Water and Sanitation District, town of Vail and the Colorado Department of Public Health and Environment.

In mid-September, there was a large die-off of fish in Mill and Gore creeks, and accidental discharge from a tank used for snowmaking on Vail Mountain was suspected.

On Sept. 20, Vail Resorts was contacted by the Eagle River Water and Sanitation District, which had noticed an abnormally high water demand in the core Vail area over the previous weekend. The sanitation district narrowed down the high use to a storage tank that is used by Vail Resorts for its snowmaking system.

According to a memo, Vail Resorts discovered that a few valves on the snowmaking setup had been left open since March. On Sept. 20, the valves were shut, which stopped the discharge of water to Mill Creek. The state public health department received an incident report from Vail Resorts that day.

A blue tint was observed Sept. 21 in Gore Creek by Parks and Wildlife and the town of Vail. The discharged water was blue-gray, and bugs, fish and algae had been killed in 1,500 feet of the creek.

Parks and Wildlife officials visited Vail on Sept. 21 to investigate and took water samples. Officials recorded 120 dead fish.

“Based on discussions with Vail Resorts, we learned that the spilled water to the river is a combination of potable water and pond water with algaecide, which in this case was toxic to fish given the dead fish,” MaryAnn Nason with the state health department said. “While events that lead to fish kills are an immediate concern, dead fish doesn’t always mean there is an urgent public health threat.”

The fish were surrounded by high levels of the spilled and contaminated water, Nason said.

The state health department coordinated with Parks and Wildlife for a follow up inspection Sept. 24.

As of Tuesday, Sept. 28, the state said it was still investigating the incident in coordination with local authorities to determine what violation of the state’s Water Quality Control Act might be associated with the incident.

Public health toxicologist Kristy Richardson said the state is disheartened to learn about 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.”

This story is from VailDaily.com.