Aluminum Smelter Superfund Site

Roux performed a multimillion-dollar Remedial Investigation and Feasibility Study (RI/FS) at a 1,300-acre former aluminum reduction facility (commonly referred to as an aluminum smelter) in Columbia Falls, Montana. Roux was hired as the primary environmental consultant in 2015 to perform the RI/FS in accordance with United States Environmental Protection Agency (USEPA) Superfund guidance, including evaluation of the USEPA hazard ranking system scoring of the Site, scoping of the RI/FS, development of the RI/FS Work Plan, and performance of the RI/FS at the Site.

The Site operated as an aluminum smelter from 1955 until 2009. Solid waste generated by the aluminum production process was primarily disposed in on-site landfills; spent pot liner was disposed on-site until it was classified as a hazardous waste by the USEPA in 1990, and then it was shipped off-site for disposal as K088-listed hazardous waste at permitted hazardous waste landfills. The facility closed in March 2015. Since that time, the client has completed decommissioning and demolition activities of the Site buildings. Implementation of the RI/FS began in November 2015.

The Site includes seven closed landfills, one active landfill, two closed leachate ponds, and several wastewater percolation ponds. The technical scope of work of the Phase I Site Characterization conducted from 2016 through 2017 included a geophysical survey of the landfills, landfill soil gas surveys, drilling of 95 soil borings, and installation of 43 monitoring wells, including 17 deep monitoring wells up to 300 feet in depth. The program included collection of approximately 750 samples for laboratory analysis from various media, including soil, sediment, surface water, and groundwater. A Phase II Site Characterization to fill remaining data gaps was completed in 2018.

Our investigations included a full habitat assessment, development of an ecological conceptual site model, and design and implementation of a field sampling and analysis program. Dietary models were established to determine the potential effort of historic operations on the surrounding ecosystem. The results of the screening evaluation were used to support a comprehensive ecological risk assessment for the site. Baseline Human Health and Ecological Risk Assessments were completed in 2018/2019. A Remedial Investigation Report was completed in 2019 and a Feasibility Study Report addressing six Decision Units was completed in 2021. Separately, Roux has assisted with the planning and implementation of an early removal action at former wastewater percolation ponds. All work described above has been conducted pursuant to strict Consent Order deadlines and has required review and approval from both the USEPA and the Montana Department of Environmental Quality (MDEQ).

The USEPA issued its Proposed Plan in 2023, which indicated that USEPA’s preferred site remedy was the highest ranked remedial alternative in the FS. This includes consolidation and capping of contaminated soil and sediment, and construction of a slurry wall around the groundwater contamination source area. The Record of Decision is anticipated to be released in 2024, followed by remedial design. Roux has been retained to proceed with Remedial Design Work Plan and Pre-Design Investigation Work Plan.

Roux is currently undertaking a preliminary evaluation of a potential natural resource damage claim regarding injury to human use and ecological services from the site, including a comprehensive review of the data and findings from the remedial investigation/feasibility study for the site in addition to historic, federal air and groundwater discharge permits and associated releases. Read more

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