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.
The Department of Environmental Quality is requiring Talen to run tests to determine whether the ponds can be fully dewatered and whether enough space is available to hold all the water. Additional tests must be conducted to determine whether the draining is working and whether additional aquifers are contaminating the groundwater.
Talen runs a system of wells that capture the polluted water, then pump it back up to higher ground for other uses at the plant. Those wells do not stop the leaking coal ash ponds, however, which is why a remediation plan was required.
The company is also proposing expanding this system of wells, called capture wells, and flushing out the pollution with freshwater injection.
Talen and the other five co-owners of the plant must pay a bond to cover the clean-up costs.
A Billings-based environmental group, Northern Plains Resource Council, has estimated a clean-up plan would generate 218 jobs for the Colstrip community.