Tearing Down Dam Could Unleash a Torrent of Trouble

Dismantling the dam built a century ago at the confluence of two rivers in western Montana will be the easy part. It’s dealing with the contaminated mud behind the dam -- enough to fill a freight train more than 500 miles long -- that poses the big challenge.

The Environmental Protection Agency expects Milltown Dam, at the terminus of the nation’s largest Superfund environmental cleanup site, will be taken down in the winter of 2006-07.

There’s experience to draw on in removing the aging dam -- Wisconsin has eliminated more than 100 -- but Milltown stands out for having all that mud contaminated with heavy metals, mining contamination that washed 120 miles down the Clark Fork River.

That some of the sediment will be removed is a triumph for environmental groups and others who campaigned for years to take it out. Skeptics, however, say disturbing the mud could introduce new problems.

By everyone’s account, it is a huge undertaking.

“The combination of the dam removal and sediment removal and restoration is something that I’m not aware of happening anywhere else,” said Peter Nielsen, a public health official in Missoula, a few miles downstream of the dam, who was an early activist on Clark Fork water pollution.

With the support of then-Gov. Judy Martz, the EPA last year decided that the dam at the confluence of the Clark Fork and Blackfoot rivers should come down, and that about one-third of the 6.6 million cubic yards of sediment laced with arsenic and other contaminants should be dredged for disposal 100 miles away. The contaminants leached from old mines upstream.

While some preliminary technical work is underway, most of the action is behind closed doors as the major players negotiate an agreement spelling out who’s responsible for what. EPA project manager Russ Forba said he hoped that agreement, which required court approval, would be completed this month.

Financial responsibility for the $100 million in work rests largely with Atlantic Richfield Co., which acquired assets and liabilities of the Anaconda mining company. Money also will come from the dam’s owner, Northwestern Corp.

Meanwhile, people in Bonner and Milltown, upstream and across Interstate 90 from the dam, have mixed thoughts about what lies ahead.

Cindy Jimmerson, who moved into a home on the Blackfoot River two miles from the dam five years ago, said she looked forward to the day the two rivers would be restored to a more natural state, free of the 21-foot-high dam.

She envisions the Milltown area becoming an extension of Missoula as a new community image draws people looking for affordable alternatives to the city’s real estate prices. Federal money for amenities such as trails, footbridges and an interpretive center is being sought.

Not everyone shares Jimmerson’s vision.

Mike Devlin, 41, who grew up in Milltown, regrets loss of the reservoir, where locals have fished for years. “They should just let the dam be,” he said.

Forba said that if the dam were removed in 2006-07, then the sediment probably would be taken out in 2007-08 and restoration of the area would begin in 2009.

“That’s if Mother Nature cooperates and things go as planned,” he said. “It’s an active system, so you can’t always predict.”

Water and power companies, along with the state Transportation Department, say the timetable isn’t the only uncertainty.

Mountain Water Co., which supplies 60,000 residents of Missoula, worries that the Milltown project will raise the arsenic level in the Missoula aquifer. PPL Corp. envisions contaminated sediment that is not removed eventually washing about 150 miles downstream to its dam at Thompson Falls. The Transportation Department says taking out the dam could harm roads and bridges nearby.

“We think the long-term answer is probably removal of the dam and the sediments,” said Arvid Hiller, Mountain Water’s general manager. But potential effects have not been researched adequately, he said.

Nielsen, water quality supervisor for the Missoula City-County Health Department, said that the aquifer issue had been investigated and that the findings did not support Hiller’s concern. As for PPL’s dam, Nielsen said the Clark Fork was much bigger downstream than at Milltown, and the amount of sediment carried to Thompson Falls would be insignificant relative to the water volume there.

Liability for potential road and bridge damage apparently is part of the confidential decree negotiations.

Arco advocated upgrading the dam and leaving the sediment in place. The company still maintains that would be the “technically sound” thing to do, but is moving forward with removal plans now that the decision has been made, said Robin Bullock, Arco’s regional manager in Butte.

Considerations in the debate over whether to remove the dam and sediment included the bull trout, which is on the federal threatened species list. Milltown Dam and a nearby, smaller dam also to be removed block the bull trout migration to spawning grounds. Milltown Reservoir supports illegally introduced northern pike, which prey on trout.

Concerns about the dam and reservoir surged in 1996 after shifting ice scoured the river bottom and stirred contaminated sediment. The emergency release of water at the dam, to deal with the approaching ice, flushed some sediment downstream. Copper concentrations in the water rocketed and surveys found a steep drop in rainbow and brown trout numbers. Opinions about the cause were mixed.

Nearly 10 years later, Nielsen sees the upcoming work at Milltown as “an opportunity to create a long-term asset where once there was a liability.”

“The rivers won’t be back to the way they were because there’s a town there now, an interstate, railroad crossings, there’s a lumber mill there,” Nielsen said.

“The plan is to restore as much of a naturally functioning river as possible. For an environment like this, close to a city, this is a tremendous opportunity for environmental restoration.”