Cleanup may add sediment to CF River

THOMPSON FALLS, Mont. - An important step is taking place this week in the cleanup process at the Milltown Reservoir Sediments Superfund site, east of Missoula, and the results will have some impact on the Clark Fork. On Tuesday the river was diverted into a bypass channel so that next week the coffer dam can be breached, allowing the Clark Fork to flow freely for the first time in 100 years.

Russ Forba of the Environmental Protection Agency and Keith Large of the Montana Department of Environmental Quality met with the Sanders County Board of Commissioners in Thompson Falls Thursday to explain how the cleanup project will affect the Clark Fork and those who live near it. Forba and Large are project managers of the Milltown cleanup and they said an increase in harmless materials in the river is what Sanders County residents can expect.

The commissioners expressed concerns that the particles will affect fish populations and Forba said they would not.

“I look at the biggest impact down here as another 500,000 tons of material being deposited,” Forba said. “It'll take up space in the reservoir.”

Forba said the river may appear murky but because the breaching will take place around the time of high-flow, murkiness will be seen anyway. He told the commissioners they will probably be able to spot the increase in particles because they will know to look for it.

“The common guy on the street may not even notice,” Forba said. “Then once the high flow comes you won't even notice it at all.”

Large said the effects of the breaching will be felt much more considerably down in Superior because they do not have the luxury of the Flathead River. The Flathead flows into the Clark Fork near Paradise and will dilute the water significantly when there is an increase in materials.

Project managers for the Milltown cleanup project also spoke at a meeting in Mineral County last week where several concerned outfitters appeared to voice questions and concerns about the impacts on the fishing season. Forba and Large said their will be some short-term impacts on aquatic life immediately following the breaching but the people around Missoula will get the worst end of the deal. Large said a temporary decline in fish populations is expected because of an increase in stress-not because of metals in the sediment.

“The biggest effect will be from the dam down to the confluence of the Bitterroot,” Large said.

Forba said the project managers want to keep the people informed when a major phase in the project is taking place, especially when scouring is expected. He was referring to the 300,000 tons of clean sediment from the Blackfoot River that will scour downstream when the coffer dam is breached during the week of March 24.

In 1908 a massive flood washed mining wastes from Butte to the Milltown Dam where they were deposited and arsenic eventually contaminated the Milltown aquifer. Copper sediments also periodically killed fish and in 1983 the site was listed as a federal superfund site.

The overall goals of the Milltown Dam cleanup project are part of a “long-term vision” Forba spoke of to improve fish life and clean up the Milltown Reservoir. According to the EPA's Web site, the cleanup process will excavate approximately 2.2 million cubic yards of the most highly contaminated sediments in the reservoir and restore the town's drinking water supply. The removal of the dam and powerhouse will in-turn allow unrestricted fish passage and “return the Clark Fork and Blackfoot Rivers to a more natural and free-flowing state.”

Forba said there are many protective measures in place to help minimize environmental impacts and one key measure is the use of the bypass channel-the construction of which began in 2007 and took about a year to complete. Forba presented to the commissioners Thursday that the bypass channel is preventing the scouring of 450,000 tons of sediments with high metals concentrations. He said the engineering controls and BMPs (best management practices) this project is using exceed any other dam removal in the country and perhaps the world. He said $11 million has been spent on the bypass channel and the flood berms alone.

The cleanup project began in 2006 with the construction of infrastructure and in January 2008, the demolition of the powerhouse took place. The excavating and hauling of sediment began in 2007 and is expected to last until 2009. The restoration phase of the project is scheduled to last through 2011.

Project schedules, releases and updates are available at the EPA Web site at www.epa.gov/region8/superfund/mt/milltown.