Crews fix dangerous Bitterroot diversion dam

Crews fix dangerous Bitterroot diversion dam

Source: NBC Montana
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By: Kevin Maki

CORVALLIS, Mont. – Despite rain and some flooding, construction crews are making good progress fixing a dangerous diversion dam in the Bitterroot River north of Corvallis.

The Supply Ditch diversion dam has been the site of numerous water accidents through the years including one drowning.

Crews are working to make the dam safe for people who use the river for recreation.

For years now signs along the Bitterroot River have warned floaters to portage around the dam. Boaters caught in the dam could find themselves trapped against the face of the dam, making it extremely difficult to swim out.

Construction crews are altering the dam to eliminate the dangerous current. Over time the stream current has eroded or “scoured” the stream bed.

“We are importing riprap, and we’re replacing it below the diversion dam,” said project engineer Ken Fields, “which is basically to do two things. It’s preventing further scour, and it’s also decreasing slope below the dam.”

It should make that stretch of river safe.

Crews have temporarily diverted water from the site so they can work on the dam. About 1/4-mile upstream you can see where water has been temporarily diverted to the west, while leaving some water flowing toward the Supply Ditch diversion. Concrete barriers are laid across the river and shored up with gravel.

Keeping some water flowing north is necessary to protect aquatic micro-organisms.

The Supply Ditch supplies water to agricultural irrigators. Crews had some down-time last week because of flooding.

“Currently we are trying to beat the runoff if the weather increases in temperature,” said Fields, “and we get more rain.”

NBC Montana met Corvallis resident Shannah Shull, who said she loves taking her family on the river. For Schull, having the dam fixed is peace of mind.

“It’s huge piece of mind,” she said. “I love my kids, and I wouldn’t want anything to happen to them. Having it fixed will do wonders.”

The bulk of the project is expected to be completed in March.

It’s estimated the Supply Ditch diversion project will cost between $325,000 and $350,000. It’s paid by state and federal grants, the Supply Ditch irrigators, the Bitterroot Conservation District, Montana Fish, Wildlife and Parks and Trout Unlimited.