Mountain Water purchase provides chance to remove Rattlesnake Dam, improve fishery

As the new owner of Missoula's drinking water system, the city on Tuesday announced plans to remove the lower Rattlesnake Dam, eliminating a structure that has blocked the passage of fish and other wildlife for more than 100 years.

With the cold waters of Rattlesnake Creek rushing nearby, Mayor John Engen and several City Council members joined Trout Unlimited and Montana Fish, Wildlife and Parks in detailing the dam's removal, along with their plans to restore the waterway to its natural condition.

“The fact of the matter is, this dam serves no practical purpose,” Engen said. “It impedes wildlife and it's fenced off from humans and wildlife, and it's our intention to bring this area back to a free-flowing stream and restore it the best we can.”

The dam is one of several obstructions spanning Rattlesnake Creek and sits roughly six miles from the confluence with the Clark Fork River. The structure was one of many assets acquired by the city in its purchase of Mountain Water Co. earlier this year.

The purchase, which closed on June 22, has positioned the city to make improvements to both the public utility and the environment, Engen said.

“Now that we own the system, we realize there are additional benefits beyond simply engaging in service delivery,” Engen said. “We have a chance to do the right thing here. We have partners who are going to make this place new in the old way.”

Rob Roberts with the Montana chapter of Trout Unlimited said the crumbling concrete dam has been a problem for the local fishery for years. Removal of the structure has always piqued the interest of the organization and its backers, though it loomed out of reach for many years.

Back in 2002, efforts were made to mitigate the dam's blockage and the environmental problems it caused. A fish ladder was installed, though Roberts said it was only partially successful.

“Rattlesnake Creek has been an extremely important fishery in terms of the overall health of the Clark Fork River,” said Roberts. “A lot of the fish people catch in the Clark Fork or even the Blackfoot ultimately come from this stream.”

The species range from brown trout to rainbows and cutthroat, making the cool, rocky stretch of the Rattlesnake a highly productive stream in maintaining a healthy, native fish population.

But for the past 115 years, the dam has served as an obstruction. It now includes a concrete wall and a large retaining pond surrounded by a concrete wall. At low flow, some fish species are able to navigate the dam's spillway, while others cannot.

At runoff, when most of the fish spawn, the dam becomes impassable.

“We first realized that removing the dam was a possibility during acquisition proceedings, when the city's experts were testifying that everything here had no functionality to the system,” said Roberts. “We have a vision for a free-flowing Rattlesnake Creek that connects from the headwaters all the way to the confluence of the Clark Fork River.”

Dennis Bowman, a 25-year employee of Mountain Water who now serves as superintendent of Missoula Water, said the dam has been an issue for years, even under prior ownership.

The structure was first erected as a wooden dam around 1902, though it was converted to concrete in 1924. The creek remained a source of drinking water until a giardia outbreak in 1983. At that point, it was taken off the system.

More recently, Bowman said, the dam's failing walkway was removed, prompting the removal of the gear mechanism and motors that operated the slide gates. With the gates now permanently open, the spillway becomes an impassable water jet during the spawning season, when the fish need passage most.

“It did affect how the fish were not able to go up the river,” said Bowman. “Removing this (dam) is a great deal. I've been involved with some of the maintenance on here, and I know the cost of that maintenance. The water here isn't needed for the system.”

While the structure's removal and restoration doesn't yet carry a price tag, Trout Unlimited plans to help cover much of the cost, something it has done for other dam removals and mining reclamation projects in the state.

The Westslope chapter of Trout Unlimited and Stockman Bank have already offered a $20,000 matching grant to kick off the project's data collection, which serves as the first step in removal.

“This is a 45-acre chunk of land, and it's going to be a huge addition to our Rattlesnake greenbelt as a whole,” said Morgan Valliant, the city's conservation lands manager. “When looking at this site, we're looking at full-scale habitat restoration. There's going to be a huge benefit, not only for the fisheries but also to the other animals that use the area.”

Ladd Knotek, a biologist with Montana Fish, Wildlife and Parks, has been working on a solution to the dam for nearly 15 years. While the fish ladder installed in 2002 was a good effort, the dam's full removal could restore the creek's lower reaches, he said.

“We had a complete fish barrier, and it's precluding the movement of fish from the Clark Fork River to about five to six miles of prime spawning habitat,” said Knotek. “What we're missing is that connectivity with the river to access the spawning areas.”

Valliant said the project could begin later next year or in early 2019.