Montana Dam Replacement Project Reached Halfway Point

Construction crews have reached 50 percent completion on a new concrete diversion dam system near Babb.

Updated on Sept. 28, 2026 in Home Renovation

Screen-print poster illustration showing a massive concrete diversion wall in a rugged river landscape, symbolizing Montana infrastructure development. — Construction crews have reached 50 percent completion on the $100 million federal project to replace the aging St. Mary Diversion Dam near Babb, Montana. AI Illustration. Upload story photo >

Live Poll

Should the federal government prioritize funding the replacement of aging local water infrastructure?

The 110-year-old St. Mary Diversion Dam is being replaced with modern concrete infrastructure to address severe deterioration. The $100 million federal project serves the regional Milk River irrigation network.

Why it matters

Replacing the crumbling 1915-era dam prevents failure of critical local water supply infrastructure following a 2024 siphon collapse. The new build also integrates environmental upgrades to protect local river species.

The project replaced a 198-foot-long, 6-foot-high concrete weir that had been in service since 1915. Work is currently 50 percent complete, with full project completion expected by late 2026.

The players

Milk River Project

A vital regional irrigation network that relies on the diversion of water from the St. Mary River.

The details

Workers are dismantling the corroded, century-old concrete headworks to install a modernized diversion structure. To allow for continued water flow during the process, water is being routed through a temporary canal. The new design includes a fish screen and bypass system, which physically prevents fish from entering the irrigation system, ensuring compliance with the Endangered Species Act.

1915: The original St. Mary Diversion Dam and Canal were completed.
2024: The St. Mary siphon failed, triggering federal funding for the project.
End of 2026: The project is expected to reach final completion.

The Home Front

This project represents a broader trend of upgrading aging federal water infrastructure that has exceeded its intended 100-year design life. Such improvements are critical for maintaining the reliability of regional irrigation networks and ensuring environmental regulatory compliance.

Residents served by the Milk River Project should monitor local water district notices for any temporary delivery adjustments during the final phase of construction. If your property relies on irrigation water, ensure your private intake valves are maintained and clear of debris as system flows fluctuate.

The takeaway

Maintaining 110-year-old infrastructure requires proactive replacement to avoid emergency failures like the 2024 siphon collapse. Landowners connected to regional water systems should keep records of their local irrigation district contact information to receive updates on service disruptions.