Brooks Priest stands next to a massive beaver dam 12 feet above the churning waters of the Blackfoot River. When workers breached the Milltown Dam on March 28 this year, falling water levels left the beavers high and dry. Armed with a mean hoedag swing and a resource conservation degree, Priest has worked to restore rivers across the West, and her latest project is here at Milltown.
"If only the beavers could teach the human engineers," the keen-eyed, wiry Priest says, looking up at the giant mound of sticks. She has a soft spot for "nature's engineers," she says: "They're the real restoration experts."
The Milltown Dam, built in 1907 at the Clark Fork-Blackfoot confluence near Missoula, once submerged about a mile of the Blackfoot's narrow floodplain and the Clark Fork's wide valley. After the dam went up, millions of tons of arsenic and toxic tailings collected behind it, washed down from copper, silver and gold mines near the Clark Fork's Butte headwaters. In 1983, 120 miles of the upper Clark Fork basin were designated as a Superfund site. The Milltown dam removal was a key part of the Superfund cleanup, and now that it's gone, a levee diverts the river into a straight, riprapped channel.
Behind the levee, bulldozers scrape toxic muck out of rectangular pits, and freight cars haul it 150 miles upstream to dump. Above the diversion, the river splits and reconverges in a tangle of silver threads around sandbars littered with toppled birches and alders. High flows this year ate away huge swaths of bank and obliterated several large islands.
The Clark Fork is sick, and no one is sure how to heal it. All agree on the need "to get the poison out of the wound," says Joel Chavez, an engineer with the Montana Department of Environmental Quality's abandoned mines program. But there's scant consensus on how to turn a sterile and mutilated floodplain back into a functioning river, here at Milltown or anywhere else in the West.
The $10 million Milltown project exemplifies the re-engineering approach, where crews will bulldoze a new channel after Superfund contractors remove tailings. But some river experts say we should devote more of the $2 billion spent yearly on U.S. river restoration to understanding how rivers like the Clark Fork work. Then we can take action that may not require re-engineering.
Sometimes excluding livestock from riparian areas, or removing key levees and dams to restore flood patterns and sediment movement, is enough to permit degraded rivers to heal themselves. River experts point to Oregon's Sandy River, which quickly washed accumulated sediment downstream after Portland General Electric blew up Marmot Dam last fall. Coho salmon swam past the dam the day after it was breached, and spawning habitat has greatly improved.