MISSOULA – The federal government has hauled away 2.2 million cubic yards 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 ago at the confluence of the Blackfoot and Clark Fork Rivers outside Missoula.
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.”
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 but eventually have been able to pass, 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.”
Overall, removing Milltown Dam is a boon to Clark Fork fisheries by increasing the free-flowing portion of the river, allowing more fish movement and opening more spawning areas, Saffel said.
Sediment still degrades fish habitat and aquatic insect production from the Milltown Dam site down through Missoula, he said. But the impacts disappear downstream from the confluence of the Bitterroot River, he said.
“By the time you get down to Superior and St. Regis, there appears to be very little impact,” he said.