Flathead River Returned to Natural Channel at CFAC Superfund Site

The Flathead River is once again flowing naturally through the former home of the Columbia Falls Aluminum Co. (CFAC) after site workers completed an early remediation project on March 19, six weeks ahead of schedule.

The years-long investigation and cleanup effort at the Superfund site is approaching its final stages as remediation teams await feedback from the Environmental Protection Agency (EPA) and Montana Department of Environmental Quality (DEQ) on a draft feasibility study that was submitted in October 2020. The EPA is expected to issue a record of decision on the study in the first half of 2022, at which time full remediation work is expected to begin. The property was declared a Superfund site — a designation given to sites the EPA considers most critical to clean up — in 2016, years after a number of toxic contaminants, including cyanide, were detected in soils, surface ponds and groundwater. CFAC closed in 2009.

One piece of that remediation effort was green-lit early, however, and workers began tearing down a decades old barrier that re-routed the Flathead River away from the south percolation pond. Contaminants were later discovered in that pond, which was built in the 1960s to manage process wastewater and storm water, and site managers were worried that the sheet pile wall and riprap bank stabilization installed to keep sediment out of the river could be insufficient in flood conditions.

The EPA approved site managers’ proposed solution as an early remediation project, and late last year the contaminated sediment from the pond was dug out and removed. The second phase of the project, the removal of the sheet pile wall and riprap, began in late February and was completed in less than a month. As a result of the removal of the manmade barriers, the Flathead River is now flowing in its natural channel.

“We’re extremely pleased with this work,” CFAC Project Manager John Stroiazzo wrote in a press release issued on March 30. “This early action is a benefit to the Flathead River and is another example of meeting our commitment.”