Anaconda Aluminum Co Columbia Falls Reduction Plant

Overview

The Anaconda Aluminum Co Columbia Falls Reduction Plant operated from 1955 to 2009 in Flathead County, Montana. The EPA added it to the National Priorities List (NPL) in September 2016. The NPL is the federal list of hazardous waste sites that qualify for long-term cleanup under the Superfund program. A remedial investigation completed in 2020 and a feasibility study completed in 2021 laid the groundwork for a cleanup plan, which the EPA and Montana Department of Environmental Quality (DEQ) finalized in a Record of Decision (ROD) signed January 10, 2025.

The site contains 17 contaminants of concern spread across soil, groundwater, surface water, sediment, and sludge. Key contaminants include cyanide, fluoride, polycyclic aromatic hydrocarbons (PAHs), and metals such as lead, cadmium, thallium, selenium, and zinc. The primary source of cyanide is spent potliner, a hazardous byproduct of aluminum smelting that was buried on site and can leach into groundwater. Fluoride and cyanide are concentrated in the West Landfill and Wet Scrubber Sludge Pond, while PAHs and metals are found near percolation ponds and the main plant area. Groundwater contamination poses a risk of migrating toward the Flathead River, though contamination has only been detected in a backwater seep area and riparian channel, not in the main river itself.

The $57 million cleanup plan calls for a slurry wall to fully surround buried spent potliner and stop contaminants from spreading toward the Flathead River. It also includes excavation and consolidation of contaminated soil, engineered caps to seal affected areas, groundwater extraction wells, infiltration basins, and institutional controls to restrict future site use. A removal action at the South Percolation Ponds was already completed in 2021. Remedial design work began in August 2025, with construction expected to start between December 2026 and February 2027. The EPA is currently negotiating a Consent Decree with the responsible party to carry out the cleanup. Human exposure is not currently under control, and groundwater migration is not yet stabilized, according to EPA performance measures. Portions of the site found to be free of contamination were sold to a local developer in 2024.

Community members can stay involved in several ways. The EPA holds regular community meetings and informal coffee hours in Columbia Falls. A Community Liaison Panel meeting was scheduled for May 27th, with coffee hours on May 28th. The EPA also provides fact sheets and email updates. In December 2024, a Technical Assistance Grant was awarded to the Coalition for a Clean CFAC so the group can hire a technical advisor to help residents understand the cleanup process. The Community Involvement Plan from 2017 will be updated in 2026. Once the Consent Decree is available, the public will have a chance to review and comment on it. Site documents can be reviewed at the ImagineIF Library in Columbia Falls or downloaded through the EPA's website.