MTPR

Milltown Dam Wouldn't Have Contained Missoula Flood Waters

May 14, 2018

This spring Missoula celebrated the 10th anniversary of the removal of the Milltown Dam on the Clark Fork river east of town. Now, some people are saying that the old dam could have mitigated some of this year’s flooding.

The Milltown Dam was 100 years old when its removal started in 2008. At the confluence of the Blackfoot and Clark Fork Rivers, it backed up some 3 million cubic yards of contaminated mining sediments.

And there are those in Missoula’s flooded Orchard Homes area who believe that if it still stood, their neighborhood would be the better for it.

John DeArment, the Clark Fork Coalition’s science director respectfully disagrees.

“We’re sure sympathetic to the folks out in Orchard Homes who are seeing that flooding, But the truth is that the dam, even when it was originally constructed, was a run-of-the-river reservoir. It had no capacity to store the flood flows of the Clark Fork River.

“What we probably would be seeing is continued risk of catastrophic failure of the dam and a major flood in Missoula. Even on a more routine basis, the scour of those toxic sediments that would still be upstream of Missoula and deposition of those sediments in the areas that are now flooding. So, the folks in Orchard homes would have both flood waters to deal with and toxic sediments in their yards."

Meanwhile, downstream in Frenchtown, local and federal contractors are watching a 2-mile earthen berm sitting between the raging Clark Fork and the closed Smurfit-Stone pulp and paper mill.

That berm is supposed to protect unlined toxic waste dumps in the river’s historic flood plain, but it is not engineered to modern specifications.

DeArment toured the site Monday.

“So far, given the high flows that we’ve seen, it does not seem to be in any danger of failure or of overtopping.”

The Clark Fork Coalition ultimately wants to see the defunct plant’s waste cleaned up.

"Ultimately that would allow the removal of that berm, the restoration of the floodplain out there and ultimately some economic revitalization of the site in the drier areas.”

Local and state officials are asking the EPA to grant Superfund status for the site.