HELENA –The federal government has hauled away millions of tons of toxic sediment and removed a reservoir as part of a Superfund site cleanup in southwestern Montana’s fishing country, only to encounter a hitch — the changes may impede a threatened species of trout.
The 100-year-old Milltown Dam was part of a large area of southwestern Montana that has been designated the nation’s largest Superfund cleanup site, holding back a century’s worth of toxic waste that flowed from the mines and smelters in Butte and Anaconda.
The Environmental Protection Agency’s $100 million-plus cleanup breached the dam two years at the confluence of the Blackfoot and Clark Fork Rivers outside Missoula, a part of Montana made famous by the book and film “A River Runs Through It.” Last year, workers finished hauling away 2.2 million cubic yards of toxic sediment that had built up over the years.
But now the Blackfoot River’s lower water level and work on the piers that support the Interstate 90 overpass near the site have created a narrower, faster-moving channel that makes it difficult for bull trout to navigate, residents say.
“The problem is with the pier. It’s impeding fish passage and potentially poses a risk to boater safety,” Bonner resident Bruce Hall said Friday. “It’s a costly issue, and depending on how they remedy the situation, it’s going to add to what they do.”
Bull trout were listed as threatened by the U.S. Fish and Wildlife Service in 1998 because of their declining numbers. Montana fisheries officials say bull trout can still be found throughout their historic range, mainly the Clark Fork and Flathead drainages, but are a sensitive species that do not tolerate high sediment levels in their spawning streams.
Besides bull trout, westslope cutthroat, rainbow and brown trout are also found in the river, along with mountain white fish and large-scale suckers, said Pat Saffel, Montana Fish, Wildlife and Parks’ fisheries manager for the region.
Saffel said no immediate action was necessary. Most of the time, the fish can pass by the bridge piers just fine, he said. When the water flow is a little higher than normal, the fish have been impeded for a period of time but eventually have been able to pass, he said.
Officials are waiting to see what happens at very high water flows. They must be cautious because of the threatened status of the bull trout, he said.
“When you have a fish that’s low in number, stopping just a few of the fish can have a significant effect on the population,” Saffel said. “I’m pleased the EPA is going a step further and looking at this in depth.”
Removing the reservoir restored the rivers’ flow but it also dropped the water level by 29 feet, said Diana Hammer, the EPA’s project manager for the Milltown Dam site. That exposed more of the bridge piers in the water, a problem exacerbated by reinforcement work done on the piers themselves.
The EPA and state and local officials held a meeting last week for concerned residents at which different proposals were suggested. Those included steepening the slope of the banks under the I-90 bridges or putting in a vertical wall that would hold the embankments back, widening that stretch of the river.
But those proposals are preliminary, Hammer said. More study of both the species’ movement and the proposals are still needed, she said.
One option not under consideration is replacing the I-90 bridges, Hammer said.
“Right now, I think we need to better understand if there is a problem, what it is,” she said. “We’re trying to better understand these issues.”
More remedial and redevelopment work remain in the Milltown cleanup project, which is expected to end in 2011.