The Montana Department of Environmental Quality has approved a $107 million plan to clean up the toxic coal ash pounds outside the Colstrip units 3 and 4.
The plan for Colstrip operator Talen Energy would remediate the high levels of sulfates, boron, selenium and heavy metals that have been disposed into 462-acre ponds over decades of mining and burning coal.
Environmental regulators estimate the ponds leaked 400,000 gallons of contaminated water daily.