Siphons break in St. Mary Diversion

A siphon on the more-than-100-year-old system that provides much - almost all, in drought years - to the Milk River broke Monday, shutting down the system.

The Montana Area Office of the Bureau of Reclamation area manager said Tuesday the bureau was waiting for the water to finish flowing out of the breached siphons on the St. Mary Diversion and Conveyance Works and is working to get a feel for impacts caused by the breach and looking at possible models for replacement or partial repair.

"We're currently in an analysis, data gathering stage and we're going to be in that posture for at least a week before we can plot some paths forward," Area Manager Ryan Newman said in an interview with Havre Weekly Chronicle.

He said a top priority right now is keeping people out of the area of the breach to maintain public safety.

"Our immediate response is to keep the public away and wait for the flow event to pass and the ground to dry up a little bit so we can actually get in there and start assessing our path forward," Newman said.

Ryan said Tuesday that the water already diverted to the canals should have been running out of the breach by Tuesday afternoon.

The system, part of the Milk River Project authorized at the start of the last century, provides water for more than 120,000 acres of irrigated cropland and municipal water for Havre, Chinook and Harlem, as well as recreation on the Milk River and reservoirs that are part of the project like Fresno Reservoir west of Havre and Nelson Reservoir northeast of Malta.

Nelson said Fresno Reservoir right now is near full, and the breach should not have an immediate impact on the towns that use the water or the irrigators.

He said the breach was discovered Monday morning after BOR staff had already done an inspection and went back out and saw something didn't look right.

One of the siphons - the system has two siphons - had burst, Newman said.

The breach was reported at 8:45 a.m. Monday.

BOR said in a release Monday that emergency response teams were deployed to contain and evaluate the damage.

"Flooding has caused localized property damage in direct proximity to the breach, impacted local infrastructure, and may pose risks to public safety," Monday's release said. "Roads are closed, and utilities may potentially be disrupted in the affected areas. Traffic cones and caution tape have been placed to limit access to potentially dangerous areas.

Newman said Tuesday that after the breach occurred, BOR contacted the landowner below the siphon to let them know to move livestock, then set up a perimeter to keep people away so they would not be hurt.

He said water from the breach flooded the property known as Hook's Hideaway, a motel hand horse boarding location on the St. Mary River below the siphon, but BOR is not aware of any injuries.

He said the water had cut a new channel to the river later Monday and all water was flowing there.

The siphon was running at its maximum amount of 600 cubic-feet-per-second when the breach occurred, Newman said. BOR staff immediately went to the diversion and turned off the diversion of water from the St. Mary River, but it is a nine-mile reach from the diversion to where the breach occurred. That water still had to flow through the system to the breach, he said.

The water coming from the siphon softened the ground and caused erosion, leading to the second siphon also breaching.

He said the water is likely finish running through by this afternoon, and then BOR will wait for the area to dry up so it can start doing a detailed assessment and start planning actions to take.

He said the possible actions would be a full replacement of the siphon - adding that that would not be likely this summer - or partial replacement or taking no action this summer.

He said BOR will be assessing how much water is available in the system including in Fresno and Nelson reservoirs.

He said this will be shortened irrigation season, although the recent rains have reduced demand at this point.

It will be at least a week before BOR can plot a path forward, Newman said.

Officials react

Officials reacted quickly to the situation.

Gov. Greg Gianforte said in a post Monday on X, formerly known as Twitter, that he was actively monitoring the situation and that the state is workin g with local and federal authorities to intensify the extent of damage to the surrounding area and to water users.

Sen. Steve Daines posted on X Monday that he is keeping in close contact with authorities and had contacted local irrigators as well, urning people to stay vigilant and stay away from the affected areas.

"The damage is serious, and I'm standing by to help local authorities in any way necessary," he posted.

Rep. Matt Rosendale said in a release Monday that he had been in contact with the Milk River Project Joint Board of Control, adding that he was thankful no one was injured in the catastrophe.

"I'm monitoring the failure of the St. Mary Siphon and have pressed federal officials for immediate attention to the situation," U.S. Sen. Jon Tester, who negotiated funds to repair the diversion and conveyance works into the Bipartisan Infrastructure Bill, said in a post on X, formerly known as Twitter. "As the full extent of the damage is evaluated, I'll continue to be in touch with local leaders and encourage folks to remain away from the affected area."

Tuesday, Tester said he is pushing the administration to take quick action.

"The timing of this failure could not be worse because hundreds of farmers and ranchers are currently depending on the Milk River Project to irrigate their crops," a release said Tester wrote in a letter to Secretary of the Interior Deb Haaland and Secretary of Agriculture Tom Vilsack. "This is a disaster that requires the immediate and full attention of the Department of Interior and the Department of Agriculture. I ask that you swiftly work to ensure that the local community and the irrigators have the resources they need to confront the challenges that lay ahead."

A system in need of repairs

The St. Mary Diversion and Conveyance Works was one of the first projects BOR was authorized to build after it was created at the start of the last century.

Completed in 1915, the system takes water diverted from the St. Mary River by a diversion dam near Babb through a 29-mile series of siphons, canals and drop structures, mostly on the Blackfeet Indian Reservation, to the North Fork of the Milk River, which then flows into Canada before returning into Montana.

It provides 40 percent to 60 percent of the water flowing through the Milk River in most years, as much as 90 percent or more in drought years.

Before the diversion was built, by fall the Milk River dried up in 6 out of 10 years.

Users have been warning for decades the system was close to collapse.

About 2000, users began warning of the chance of a catastrophic failure of the system.

Created as an irrigation system, all of the funding for the operation and maintenance of the Milk River Project came from users, primarily the irrigators.

The system had been patched together for decades by 2000, and the irrigators said it was close to failure. The state created the St. Mary Rehabilitation Working Group, with the lieutenant governor an automatic co-chair of the group, to find ways to do that.

And the warnings came true. This is the second catastrophic failure to the system in less than five years, with it shut down in 2020 when one of the concrete drop structures near the end of the conveyance works collapsed.

The first of the repairs on the system, work on the diversion dam near Babb, funded through the infrastructure bill was awarded to a Montana company last week.

Newman said Tuesday that the work on the dam has nothing to do with the conveyance works and the siphons.

He said BOR has been working with the Milk River Project Joint Board of Control to start planning for work on the conveyance system, including the siphons, but that is in the early stages at this point.