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Rattlesnake Creek to flow through new channel by Labor Day

Little remains of the Rattlesnake dam and reservoir that filled the small valley for 115 years. The only remnants are a hand-stacked rock wall built in 1901 to contain the water before concrete was added, a concrete block from the west end of the dam, and a couple of stubs of pipe. (Laura Lundquist/Missoula Current)

By Labor Day, most of the labor on the Rattlesnake Dam removal project will be done.

This week, the waters of Rattlesnake Creek still flow down a straight bypass channel cut through the area that used to be the reservoir for Rattlesnake Dam. But a few dozen yards to the west, a large backhoe has worked steadily to finish digging a more contoured, meandering channel intended to be the stream’s new route.

“We’re probably 75% done with the project now. The new channel comes down from the top end to skirt below the cliff and then join the bypass channel below. They have only about 200 feet of the channel left to build,” said Rob Roberts, Trout Unlimited dam project manager, gesturing toward the rumbling backhoe from the project overlook. “Expect the channel to be done and water allowed to run in probably by Monday.”

Little remains of the dam and reservoir that filled the small valley for 115 years. The only remnants are a hand-stacked rock wall built in 1901 to contain the water before concrete was added, a concrete block from the west end of the dam, and a couple of stubs of pipe.

National and historic preservation regulations required the crews to carefully assess the site for artifacts as they dug. At one point, they discovered an old dumpsite used by past caretakers of the dam. Two boxes of decades-old beer cans, bottles and knick-knacks were carted away to the Fort Missoula Museum.

Earlier, in the spring, the old cabin was dismantled and sold to a buyer in Spokane, Wash., who bought it within an hour of the sale going live.

Roberts said he became a bit overwhelmed by the historic mitigation requirements.

“My work doesn’t usually intersect with historical buildings,” Roberts said. “That was actually harder than our environmental permitting. I was unprepared for how in-depth it would be.”

The work is almost done, but it’s hard to see the designers’ vision at this point. Except for the yellow excavation equipment, the area is mostly an irregular expanse of gray, covered in rocks and dirt. It’ll be a while before it’s obvious that the Aqua Terra restoration crew graded the reservoir into a landscape capable of supporting the eventual green of stream, wetlands and riparian areas.

A few mounds of darker dirt came from the 6 feet of muck that the crews saved from the bottom of the reservoir. It contains a lot of rich organic material and minerals from the watershed above that settled out as the creek entered the reservoir. The backhoes have started moving that into depressions that will eventually become wetlands fed by shallow side channels.

“We will do some seeding (in the wetlands). But that (dirt) should be full of seed source so it could fill in naturally,” Roberts said.

Rob Roberts of Trout Unlimited discusses the restoration work taking place along Rattlesnake Creek after a century-old dam was removed from the waterway. With some planting work, the natural process will begin to play out. (Laura Lundquist/Missoula Current)

The new streambanks sport tree trunks, roots and brush jutting from the rocky rubble. Below the dirt, those logs are 20 feet long and they’re stacked horizontally 12 feet deep, at a right angle to the streamflow. This configuration will allow them to stay in place when the stream is pushing on them at high flow, and they’ll help keep the banks from eroding.

Some of the huge logs are spruce trees that were growing near the site. The rest are slash from Lolo National Forest thinning projects in Marshall Canyon and Lolo Creek.

“We hauled in their slash piles. They don’t have to burn them and it’s good material for us. So that worked out really well,” Roberts said.

A foot or two from the stream, troughs run along the streambanks, laying bare the top layers of logs. They represent the final bit of this year’s work that won’t start until mid-October. That’s when volunteers will return with truckloads of willow cuttings to plant in the troughs.

The Canyon River Golf Course has offered to let Roberts cut some of their willows, and others will come from the city’s poplar plantation on Mullen Road. Volunteers will plant the 8-foot lengths at an angle in the troughs so the cuttings overhang the bank. Thus, they create one more layer of protection for the banks. Then Aqua Terra crews will fill the troughs back in.

“The brush is only going to last four, maybe six years. The willows by then should be 8 feet tall. So brush is your near-term stability and willows are long-term stability,” Roberts said. “We’re not trying to build something that stays exactly like this forever. We want natural processes to take place.”

Some natural processes are already taking place.

Roberts pointed out some moss already beginning to cover rocks in the month-old bypass channel. He’s seen otters and beaver in the area and a few plants are already sprouting in one of the planned wetlands.

Roberts climbed a logjam suspended over a deep pool where the new channel will merge with the bypass channel. He tossed in a small cone resembling a grasshopper.

A few seconds later, a dark slender shape rose from the depths. Roberts grinned as a 10-inch-long trout nipped at the cone before spinning back into the hole. He’s seen a lot of fish in the stream, and the hope is that one less obstacle will help migrating westslope cutthroat and bull trout return to the headwaters.

“Before, fishing was closed to the dam. There is no dam; that doesn’t mean it’s all open now. It means Fish, Wildlife & Parks has to re-designate where the closure is,” Roberts said. “There’s going to be some nice fishing in here.”

The project has gone so smoothly that the crews are about a week ahead of schedule. They have about two weeks more of work, and then they’ll get a few weeks off before the final willow planting. Roberts said he’s kind of sad to see it end – it’s been nice to work on such a beneficial project so close to home.

“I’ve been really impressed with the way (Aqua Terra) managed dewatering impacts and sediment. We’ve had a few days of cloudy water, which is kind of unavoidable. But beyond that, it’s been pretty clean,” Roberts said. “It’s a huge difference compared to what we were looking at when this all started.”

Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.