Heavy equipment operators continued to rip into the dam's powerhouse and abutment wall Tuesday, eating up a sizable chunk of the defunct hydroelectric works.
The demolition at the Milltown Reservoir Superfund cleanup site should be complete in two weeks, removing 55 percent of the entire dam and marking another milestone in the $100 million project.
When that is completed in mid-March, the Clark Fork and Blackfoot rivers will be diverted from the spillway where they are currently flowing into a bypass channel and the reservoir will be drawn down another 12 to 14 feet.
The bypass channel will send the two rivers through the powerhouse's old location, starting the process of allowing them to flow unimpeded for the first time in a century, said Diana Hammer, a spokeswoman for the U.S. Environmental Protection Agency.
It will be the first time since 1906 that fish will be able to swim upstream past the dam site.
The renewed flows will churn up a large amount of sediment this spring as the rivers return to their natural levels, which will affect fish and aquatic life, but the muddy waters should clear up within several months, project officials said.
Work also continues to remove toxic mining wastes from the reservoir area, which was declared a Superfund site in 1983.
The project's next major step comes this fall when demolition on the spillway should start, removing the last obstacle to the rivers' natural flow.
Geographically, the cleanup of Milltown Reservoir, Butte, Anaconda and the upper Clark Fork River constitute the largest Superfund project in the nation.
The project is intended to remove mining wastes from the reservoir bottom, purify the aquifer and restore native fisheries and the confluence of the Clark Fork and Blackfoot rivers.
Milltown Reservoir's cleanup, which includes creating a public park on the site, is scheduled to be completed in 2011.
Matt Fein, senior project director for Envirocon, the Missoula general contractor on the Milltown cleanup, said it was gratifying to see the powerhouse's demolition after years of scientific review, political debate and environmental advocacy.
“A lot of people have been waiting for this moment for a long time,” he said.
Reporter John Cramer can be reached at 523-5259 or johncramer@missoulian.com.
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