Mine Waste

An unremediated overbank tailings deposition area upstream of the removal area. USFWS Photo by Bill Olsen.

A similar overbank tailings deposition area 5 years after removal of the contaminated material. USFWS Photo by bill Olsen.

The Mill-Willow Bypass near Warm Springs, Montana was severely contaminated with mine waste containing very high concentrations of arsenic, cadmium, copper, lead and zinc. Historically, fish kills in the Bypass and Clark Fork River had occurred, and in 1989, over 5,000 fish were killed by overland flow during a summer thunderstorm. In addition, the adjacent 2,600-acre water treatment pond system contained over 250 acres of slickens (exposed, fluvially deposited mine waste). The Helena EC Program has provided technical assistance to the EPA for over five years during remediation of the treatment ponds and the Bypass. Fish and migratory bird exposure to the contaminants has been greatly reduced, and valuable habitat remediated. The trout population is heavily fished. Over 140 migratory bird species, including the peregrine falcon and one pair of nesting bald eagles, use the area.