Montana Replaced Aging St. Mary Diversion Dam
Construction crews have upgraded the 110-year-old infrastructure near Babb to modernize irrigation and fish protection.
Updated on Sept. 28, 2026 in Home Renovation
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Crews in Babb, Montana, have reached the halfway point in replacing a 110-year-old diversion dam on the St. Mary River. The $100 million federally funded project aims to repair corroded infrastructure and install new systems for fish passage.
Why it matters
The replacement effort ensures the long-term reliability of the Milk River Project following a major siphon failure in 2024. New concrete structures and bypass systems are also intended to align the facility with Endangered Species Act requirements.
The original dam structure measured 198 feet long by 6 feet high and served the region for 110 years. The replacement project is currently 50 percent complete.
The players
Milk River Project
This regional irrigation network provides essential water delivery for agriculture across Montana.
St. Mary River
This waterway serves as the primary source of diverted water for irrigation networks in the region.
The details
Workers are replacing the deteriorated concrete weir with modern structures while routing water through a temporary canal. The updated headworks will feature a fish screen and bypass system designed to direct aquatic life back into the St. Mary River.
Timeline
The original dam and canal were completed in 1915.
The St. Mary siphon experienced a critical failure in 2024.
The project is currently approximately 50 percent complete.
Construction is expected to be finished by the end of 2026.
Roadmap
This project represents a broader trend of upgrading century-old western water infrastructure to meet modern environmental and safety standards. By integrating fish protection into major irrigation repairs, the state is aligning legacy systems with contemporary sustainability mandates.
The completion of this project secures the continued operation of irrigation services essential for regional agricultural stability. Residents and farmers relying on the Milk River Project will benefit from a more reliable water supply once the new infrastructure is fully operational.
The takeaway
Maintaining 110-year-old civil infrastructure requires significant capital investment and adherence to modern environmental laws. Upgrading these systems early helps prevent larger, more costly failures that could disrupt regional water access.
Further reading
Learn more about local updates at Home Renovation.
Source note: This article includes information reported by KRTV NEWS Great Falls.
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