Pipe replacement delivered for St. Mary Siphon

BABB, Mont. - Reclamation received the first sections of the 90-inch replacement pipe for the St. Mary Siphon, marking a major milestone of the extensive project to restore the damaged siphon. This milestone sets the stage for replacing the critical infrastructure that delivers water to the Milk River Project, a lifeline for north-central Montana ranchers, farmers, and communities.

The St. Mary Siphon is an essential component of the Milk River Project, one of Montana's most significant irrigation systems, which serves over 120,000 acres of farmland. For the agricultural community and surrounding residents, the siphon's repair is crucial to maintaining water supplies necessary for crops, livestock, and daily living.

"This delivery of the replacement pipe is an important step in restoring a critical piece of Montana's water infrastructure," said Ryan Newman, Reclamation's Montana Area Office Manager. "The St. Mary Siphon plays a vital role in delivering much-needed water to the Milk River Project. By beginning the process of full replacement, we are ensuring the continued viability of the region's agriculture and the livelihood of thousands of Montanans."

The St. Mary Canal Siphon suffered a catastrophic failure on Monday, June 17, 2024, requiring Reclamation to stop water diversion to the St. Mary Canal. The St. Mary Canal is a vital component of the Milk River Project. It provides 60% to 80% of the water for irrigation and potable uses in northern Montana through a trans-basin diversion from the Hudson Bay watershed to the Missouri River basin.

The St. Mary Canal Siphon consisted of two 90-inch riveted steel barrels that traverse the valley from the inlet, transition to an 84-inch diameter pipe at the river crossing, and then back to a 90-inch diameter pipe as they ascend the valley slope to the outlet. It was constructed in two phases, with the downstream barrel completed between 1912 and 1915 and the upstream barrel after 1925.

The siphon has undergone extensive repairs over time due to seepage, corrosion, and buckling. However, unstable valley sidewalls have caused further movement of the steel barrels and concrete supports, leading to additional damage.

Reclamation previously awarded a contract for $88 million from the Bipartisan Infrastructure Law for the repair of the St. Mary Diversion Dam, another feature of the Milk River Project.

For more information on the St. Mary Siphon replacement project, please visit St. Mary Siphon Updates (usbr.gov).

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