From The Vail Daily (John LaConte):
An algaecide that was toxic to fish entered Mill Creek this week, the Colorado Department of Public Health and Environment has learned based on discussions with Vail Resorts.
Colorado Parks and Wildlife recorded 120 dead fish Tuesday in Mill Creek and Gore Creek in Vail, where a spill was reported to the Colorado Department of Public Health and Environment by Vail Resorts…
The department said it is inspecting Mill and Gore creeks to determine if there were possible violations of the Colorado Water Quality Control Act, Nason said.
The department coordinated with Colorado Parks and Wildlife to provide the initial investigation Tuesday. Friday’s inspection was a follow-up to that effort, Nason said…
On Monday, 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 weekend.
The water and sanitation district had narrowed down the high use to a storage tank at Golden Peak. The major customer user from that tank is Vail Resorts for its snowmaking system, which, according to a memo from the town of Vail’s Environmental Sustainability Department, is not usually online until Oct. 1.
Vail Resorts, according to the memo, discovered that a few isolation valves on their snowmaking setup had been left open since March. Maintenance had been performed on the snowmaking system on Sept. 17, which required the drain line to be opened for repair work.
On Monday, the valves for the snowmaking setup were shut, which stopped the discharge of water to Mill Creek…
The discharged water was blue-gray, and bugs, fish and algae had been killed in 1,500 feet of affected creek. Common algaecides contain copper sulfate, which is blue and can be toxic to 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,” Nason 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.
But for people or dogs playing near or in this area, Nason said the risk of health impacts are expected to be low “because much of that spilled water has been washed away and diluted as it moves downstream — otherwise we would be seeing many more dead fish downstream.”