Dam on Rattlesnake Creek to be removed as part of restoration project

Dam on Rattlesnake Creek to be removed as part of restoration project

Source: Missoulian
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It’s not taking long for the city to rearrange the furniture in what used to be Mountain Water’s home. Some of it they’re just going to toss out.

Standing beside the Rattlesnake dam Tuesday afternoon, Mayor John Engen laid out the city’s plan for the disused barrier spanning the much-beloved creek in Missoula.

“We’re going to remove this dam,” he said.

The city’s had interest from Trout Unlimited and Fish, Wildlife and Parks to lead the project, after the groups tried for more than a decade to mitigate the dam’s adverse effects on the ecosystem.

The dam, adjacent pond and park area is on 45 acres that will be added to the 100 acres of city open space already on the Rattlesnake Creek corridor, according to Open Space Lands Manager Morgan Valliant. The city hopes to expand the Rattlesnake trail, currently a thin gravel path, through the area.

From the late 1930s until the late 1960s, the area was a public park, built by Montana Power Company, with tables, benches and ballfields.

The creek serves as a spawning ground for many of the fish that swim in the Clark Fork and Blackfoot rivers, Trout Unlimited Project Manager Rob Roberts said, including bull trout, cutthroat trout, brown trout, rainbow trout and mountain whitefish.

“All those big fish in the river are coming up here trying to spawn and all those little fish are swimming back down,” Roberts said. “We have a vision of a free-flowing Rattlesnake Creek that connects from the headwaters to the confluence of the Clark Fork River.”

It would be the first time in more than a century.

The lower Rattlesnake Creek dam was built in 1905, before several others were added in the first part of the 20th century by the Montana Power Co. to create a backup water supply for the city.

The dams were sold as part of the water system in 1979 to Mountain Water Co. and stayed in place, despite the switch in the early 1980s to using the aquifer below Missoula as a water supply. That was after more than 60 cases of giardia (also called beaver fever) were reported to the City-County Health Department, and Mountain Water stopped using creek water.

In the early 2000s Mountain Water was open to helping: a fish ladder was built onto the dam at Fish, Wildlife and Parks’ urging. That helped certain species of fish get upstream for a while.

But a few years later, because of the dam’s crumbling infrastructure, the company removed the walkway and took out the sluice door mechanisms, leaving the gates open and effectively ruining any chance fish had to swim upstream outside of low-water season, according to FWP’s Area Fisheries Biologist Ladd Knotek.

“Most of the fish are moving through this in spring, at the peak of high flows, and there’s basically a jet spraying water preventing them from getting through,” Knotek said, adding there’s “always shortcomings with artificial fixes.”

So they’re going to tear it down. But not just like that.

Trout Unlimited is looking at historical records to get an idea of where the stream flowed before it was dammed, as well as how the dam was constructed, changing the way the creek behaved; not going for a physical re-creation of the creek’s old path, but rather restoring the “functions” of the creek: namely fish spawning and providing a wider habitat for amphibians and mammals.

Roberts said they’ll need to study the dam, most likely starting this winter, to figure out what kinds of sediments are built up behind it and how removing the infrastructure will affect the stream flow.

There is a 3.5 million-gallon pond to drain, after all, and Roberts said every decade or so, Mountain Water used to pull out 500 truckloads of sediment from the area.

“If we just straight up pull the dam … we wouldn’t be doing our job right,” he said. “We’re going to build it so we know what the impact is going to be.”

The fundraising will start in 2018, Roberts hoped, and estimated the project would total around $1 million. He was confident Trout Unlimited could pull that together from grants and fundraising. Restoration could start as early as 2019.

They already have one matching grant, for $20,000, enabling Trout Unlimited to start the research on the dam.

“This facility no longer serves a practical purpose for Missoula,” Engen said at the opening of the meeting. “We have partners who are going to make this place good in the old way.”