The Montana Department of Environmental Quality on Friday approved a plan for removing hazardous waste from pot-room buildings at Columbia Falls Aluminum Co.

The announcement ends months of waiting, as Calbag Metals — which purchased most of the above-ground assets at the facility north of Columbia Falls — was required to obtain permission from the state before its ongoing demolition and salvage work could proceed to the pot rooms.

The plan addresses the removal and disposal of about 26,000 tons of spent potliner, a hazardous waste containing cyanide, fluoride and other toxic chemicals.

Calbag’s scope of work on waste removal is limited to the 10-building pot-room complex and is separate from the Environmental Protection Agency’s consideration of the site for listing under the federal Superfund program. The federal agency’s decision, expected this fall, would address the larger-scale cleanup of seven landfills expected to take eight to 10 years.

Under the state-approved plan, Calbag can begin the work immediately and has two years to finish removing all hazardous waste in the 451 remaining aluminum reduction pots, along with any other hazardous waste the company encounters in the buildings.

The waste will be shipped to a chemical waste management facility in Arlington, Oregon.

Once waste is removed from a pot, the plan requires the company to ship it off-site within 90 days.

Mark Hall, the state’s hazardous materials section supervisor, said the plan became official Friday morning after Calbag’s $9.1 million bond was secured, providing the state with a financial assurance that Calbag will complete the work as agreed upon.

“That was the last piece that we were working on,” Hall said. “I’m really excited that we’re at this stage and looking forward to implementation.”

The finalized plan doesn’t quite end the state’s involvement in the waste removal. Hall said the department will continue to provide an oversight role until all hazardous waste is removed from the pot rooms.

Cliff Boyd, Calbag’s general manager for the project, told the Columbia Falls City Council on Monday that he expects to begin the removal work later this summer. He said the company could complete hazardous waste removal by fall 2017, with demolition of the main buildings following in the winter.

The project currently employs more than 40 workers, and Boyd said that number could ramp up to 70 as work continues.

To view the plan or find more information on Calbag’s agreement with the Department of Environmental Quality, visit deq.mt.gov/DEQAdmin/cfac.

The Hungry Horse News contributed to this story.

Reporter Sam Wilson can be reached at 758-4407 or by email at [email protected].