Deadly irrigation dam near Missoula awaits upgrades to help farmers, fishers and boaters | Local News


There is only one stretch of water in Missoula that is conspicuously devoid of the usual kayaks, rafts, and drift boats that fill all other stretches of the river during the warm months.

A dangerous barrier called the Grass Valley Irrigation Dam, last updated in 1960, runs the length of the Clark Fork River near Kelly Island and creates a dangerous hazard for boaters. In the summer, wooden planks stick ominously out of the water and a bubbling boil lurks behind the structure.

This means that the entire reach of the Clark Fork River from McCormick Park to where it absorbs the Bitterroot River is essentially off limits unless one is prepared to undertake a difficult portage around the dam. There are no ramp facilities to haul or properly put a boat near the dam.

“It’s a post-and-pin dam that rises and blocks the river,” said Carl Saunders, general manager of the Grass Valley French Ditch Company. “It worked fine for over 100 years, but now it’s in a pretty rough shape.”

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Because the dam requires workers to install wooden planks each summer, it is also dangerous for workers.

“We had a death four years ago where a guy walked out and drowned in the thing,” Saunders recalled grimly. “He was a maintenance worker doing repairs. It was on a real install and one of the pins jumped out.

The 32-year-old’s foot was trapped and the water rushed on him.

It’s not just humans who risk death from the dam. According to Rob Roberts, project manager at Montana Trout Unlimited, about 10,000 fish die each year because they enter the irrigation channel and become trapped there when the water dries up.

That’s why Trout Unlimited is partnering with Montana Fish, Wildlife & Parks and the Missoula Conservation District on a structural assessment project in an effort to upgrade the aging dam. The ultimate vision is to enable safe fish migration, reduce safety risks to boaters and maintenance personnel, and increase the efficiency – as well as drought and flood resistance – of the system. irrigation.

A new weir, complete with a fish ladder, fish screen and boater ramp, could cost around $2 million. None of the partner groups have that much money right now, but the US Department of Agriculture has distributed some money for a planning effort.

old problem

Built by a group of French contractors in 1905, the dam diverts approximately one-tenth of the flow of the Clark Fork River in summer and provides water to 4,000 irrigable acres and 120 different users in the Grass Valley and Frenchtown areas. .

“We basically have 70 cubic feet per second of water that basically acts like a stream,” Roberts explained. “So when you close the ditch in the fall around October, this thing traps thousands of fish. It’s trout, whitefish, suckers, etc.

It’s a huge loss of fish to the ecosystem, he said.

“Not only sport fish, but also fish that people don’t like and the food base for all the other big fish and just the general ecology of the river,” he said. “Very simply, we would rather have all of this biomass, the fish in the river, where they belong in this system than here.”

Boater safety is also a huge issue, he noted. Local tackle shops do not recommend boaters exit past Silver Park Fishing Access at McCormick Park in Missoula due to the danger. In fact, there are warning signs along the way.

A photo of the dam in mid-summer shows the wooden planks rising several inches above the waterline across the width of the river channel, with water boiling downstream.

“It’s a fairly well-known problem,” he said. “Like, you don’t want to get over that and get caught because it’s one of those low-head dams you can hear about. And actually the hydraulics alone make them super dangerous and people get caught in there.”

There is no designated portage ramp.

“You can tell there’s really nowhere to go out and portage around this thing if you’re in a raft,” Roberts said. “So generally people kind of avoid that stretch in the summer. And that sort of eliminates a prime opportunity, you know, on the lower river. This is a very underused stretch from an angling and recreational perspective.

So now, he says, they’re working with engineers and reviewing survey data to come up with design ideas for how to rebuild the structure so it meets the purposes of irrigators, workers, boaters and fish.

Saunders said he believes the dam needs to be replaced within the next five years. In the past, he said, the landowner who owns land around the dam “was unwilling” to upgrade the dam area with a boat launch to improve safety.

“It was feared that there would be more boat traffic and people tend to camp along his property there and make campfires and leave trash,” Saunders said. “He didn’t want the increased traffic. But time flies, and he told me recently that he didn’t think it would make a penny of difference if they still came here. And it’s better if they’re safe.

To block the river

The dam must be raised within a tight time frame each summer when the water drops to a certain level. Previously, Saunders said a van driver drove around and told all the local farmers that the dam would “rise on Saturday” and a group of volunteers would show up. Now, all farmers are aging and it is difficult to find workers capable of doing this specialized work on short notice. He said the new technology includes inflatable dams that simply get air pumped in at low water and deflated at high water.

“That’s what I’d like to see, but they’re the most expensive,” he said.

Roberts said it took so long to replace the dam because the project needs buy-in from irrigators.

“These guys, in the past, they weren’t really that much interested in changing the regime to deal with fisheries protection,” he said. “But now they kind of see the writing on the wall that there’s a convergence of all these issues and the potential to partner with other people to find common goals.”

Radley Watkins of the Missoula Conservation District said it would take a lot of cooperation to complete the project. There are plenty of other dams in Montana and around the country that need money too.

“You hear about aging infrastructure across the country, but agricultural infrastructure is really its own category,” he said. “It’s a system similar to what they used in ancient Egypt. It was built 100 years ago.

Roberts said modernizing the dam was a no-brainer, so Montana Trout Unlimited made it a priority.

“To me, when you layer public safety, fisheries protection, and the ability to manage drought resilience, it’s very rare to get projects like this that mostly have no opposition to the project. “, did he declare.

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