Governor Greg Gianforte visited north-central Montana this week to get an update on a key piece of water infrastructure that farmers and ranchers along the Hi-Line depend on. The Halls Coulee Siphon is a vital link in the St. Mary Canal system, carrying water that irrigates farmland across the Hi-Line.
Constructed by the Bureau of Reclamation, the St. Mary and Halls Coulee siphons are part of the St. Mary Canal system that have provided irrigation water along the Milk River for more than 100 years.
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Since then, the system has evolved into a multi-use project which provides water for municipalities, recreation, and wildlife habitat. This system accounts for 70 to 95 percent of the flows in the Milk River during periods of drought and supplies drinking water to 18,000 Montanans and irrigates 140,000 acres.
After a catastrophic failure of the St. Mary Siphon in June 2024, state, federal, local, and tribal partners worked together to secure funding to replace the broken and outdate infrastructure.
Wade Jones, president of the Hi-Line Joint Board of Control and Montana producer, said collaborative efforts between organizations, producers and leaders like Gianforte have been crucial in keeping the project moving forward.
"Governor Gianforte helped a lot on this and so, we're back to a go again. And some of the tariff stuff has got worked through. So, we're doing good. Hopefully we're, we're going hard now," Jones said.
"Hopefully we keep moving forward," he added.
Gianforte has voiced strong support for the project, calling it critical infrastructure for the state.
"I believed it was the most important piece of critical infrastructure in the state. This is why we prioritized getting financial aid, help with the border," Gianforte said.
The governor emphasized the importance of reliability and said he is eager to continue working through challenges to strengthen water delivery across the Hi-Line.
"We have communities in eastern Montana that would not exist if this project was not operated. Water is critical for production on the land, I wanted to come and check on the progress because of the importance of this Saint Mary's irrigation project. It was really a team effort to get this going," Gianforte said.
The Halls Coulee siphon project is expected to be completed by spring 2026.
"We've worked through them issues, so hopefully everything's a go and we can just go until the snow gets too deep," Jones said.
Milk River Project Overview
The Milk River Project is a century-old trans‑basin irrigation and water supply system. It diverts water from the St. Mary River into the Milk River, serving approximately 110,000 acres of agricultural land, eight irrigation districts, municipalities, tribal reservations, and wildlife refuges in north-central Montana
St. Mary Siphon & Halls Coulee Siphon
The system includes two 90‑inch riveted steel siphon barrels passing under a valley. These taper to 84 inches during river crossing before reverting to 90 inches
The downstream barrel was built between 1912–1915, and the upstream barrel in 1925–1926
The siphons faced long-standing issues including seepage, corrosion, buckling, and instability due to shifting valley walls.
Catastrophic Failure & Response
On June 17, 2024, both siphon barrels catastrophically failed, resulting in deep erosion (30–50 feet), flooding, and a halt of water delivery into the Milk River.
The Bureau of Reclamation declared an emergency extraordinary maintenance determination and prioritized a full replacement rather than a temporary patch.
According to the Bureau of Reclamation, the total replacement cost for the St. Mary and Halls Coulee siphons is estimated at $70 million, funded in part by federal funds and Montana stakeholders.
$46.5 million was secured in a Continuing Resolution at the end of 2024 to support these repairs.
Replacement Progress
The St. Mary Siphon replacement was largely completed ahead of schedule, and water flow resumed by late June 2025 thanks to urgent, coordinated efforts. Construction on the Halls Coulee Siphon began downstream while St. Mary remained operational.
With strong partnerships between the Blackfeet Nation, Milk River Joint Board, contractors (e.g., NW Construction, Sletten Construction, Pro‑Pipe) were central to timely progress. Rehabilitation included modernizing with steel piping and reinforced concrete to combat the prior structural vulnerabilities.
Work also continues on the St. Mary Diversion Dam Rehabilitation, planned through 2027, supported by over $88 million in Bipartisan Infrastructure Law funds. Future enhancements hinge on legislation supporting the Fort Belknap Water Compact ($275 million) and potential state contributions to rehabilitate the canal for the full 850 cfs capacity (current flow is closer to 600 cfs).
