Aluminum production began at the Anaconda Aluminum Reduction Works near Columbia Falls. At the time, the plant was owned by Anaconda Copper Mining Co., and initial construction consisted of two pot lines with an annual capacity of 67,500 tons.
The Anaconda Company was purchased by Atlantic Richfield Company (ARCO). ARCO sold the plant in 1985 to the Montana Aluminum Investors Corporation and announced the plant would be operated as the Columbia Falls Aluminum Company (CFAC) moving forward.
CFAC was acquired by Glencore. Glencore operated the plant during a period of evolving regulatory and economic conditions and elected to idle the facility in 2009. By the time the facility shut down permanently in 2015, CFAC was one of just 11 aluminum plants operating in the United States.
The U.S. Environmental Protection Agency (EPA) added CFAC to the National Priorities List (NPL). Sites on the NPL are often referred to as Superfund sites.
Administrative Order of Consent
On November 30, 2015, EPA and CFAC agreed that CFAC would conduct a remedial investigation/feasibility study (RI/FS), subject to EPA guidelines, to investigate the site for contamination and develop and evaluate options to address the issues.
CFAC contracted Roux, an independent environmental engineering firm, to conduct the RI, which was finalized and approved by EPA in March 2020. Roux conducted a comprehensive investigation to determine the level of contamination at the site, and their analysis found that there was no impact from the site to neighboring communities or to the main stem of the Flathead River. Roux identified two legacy onsite landfills impacting groundwater as the main environmental issue at the site.
The RI divides the CFAC site into six areas, referred to as Decision Units (DUs), for remediation.
Once the RI was approved, Roux began to evaluate remediation options and produce the FS, which was approved by EPA on June 17, 2021. As required by law, Roux used a well-established analytical method to evaluate the options for each Decision Unit in accordance with Superfund law and subsequent EPA regulations and guidance.
Roux evaluated eight options to address the landfills (Decision Unit 1) to achieve legally required groundwater quality standards. The highest ranked option was a fully-encompassing slurry wall, which is a proven and reliable method to isolate material from groundwater.
Record of Decision
EPA will use the evaluation work in the RI and the FS to select a set of preferred alternatives to remediate the site. EPA will then solicit public input on its selection and, at the conclusion of the public comment period, will select its sitewide preferred option, the final remedy for the site. This preferred option will be published by the EPA in the Record of Decision (RoD).