Siphon fails on St. Mary Diversion

Posted 2:45 p.m. Monday, June 17, 2024

Editor’s note: This version corrects that Babb did experience flooding.

U.S. Bureau of Reclamation said a siphon on the St. Mary Diversion and Conveyance Works that provides much of the water to the Milk River each year breached about 8:45 this morning, causing flooding at a motel and shutting down the diversion.

"Emergency response teams have been deployed to contain and evaluate the damage," Ryan Newman, Reclamation's Montana Area Office manager, said in a release. "Water flows were naturally diverted back to the St. Mary River and helped mitigate the potential for additional flooding in the surrounding area."

The release said flooding has caused localized property damage in direct proximity to the breach, impacted local infrastructure, and may pose risks to public safety. 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.

Diversions to the canal were 600 cubic feet per second (cfs) at the time of failure, the release said. Diversions have been stopped, however, flows are expected to continue for as long as 24 to 36 hours while the canal drains.

"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."

Rep. Matt Rosendale is in contact with the Milk River Project, a release said, noting that uthorities ask everyone to stay out of the area while the damage is still being evaluated.

"Thankfully no Montanans were injured in this catastrophe earlier today," Rosendale said in the release.

The BOR release said the breach has affected residents and surrounding communities directly or indirectly. Emergency response teams and local law enforcement are involved in the response efforts. The Bureau of Reclamation is coordinating with the Gallatin County Sheriff's Department, Blackfeet Tribe, National Park Service, Glacier County Sheriff's Department, and Glacier Electric to limit the impacts of the breach and ensure people remain safe.

The flooding has caused localized property damage in direct proximity to the breach, impacted local infrastructure, and may pose risks to public safety. 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.

Reclamation and local authorities responded quickly to the breach and will be conducting damage assessments to the St Mary system, local property, and surrounding areas, the release said. Residents are advised to avoid the area and follow evacuation or safety orders from local authorities.

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.

The system was built to provide water for irrigation - for more than 120,000 acres - but also provides municipal water to Havre, Chinook and Harlem and provides recreation opportunities in the river and in reservoirs like Fresno and Nelson.

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

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.