Pipestem Dam spillway upgrade finished, boosts flood protection for Stutsman County
Pipestem Dam’s new spillway gives Stutsman County a stronger backstop against extreme runoff after a $250 million rebuild that moved 150,000 cubic yards of concrete.
A major flood-control upgrade at Pipestem Dam is now complete, giving Stutsman County a sturdier defense against the kind of extreme runoff that can threaten farms, roads and homes downstream from Jamestown.
The U.S. Army Corps of Engineers, Omaha District, marked the finish of the three-year Spillway Modification Project on Tuesday with local and state officials at the site north of Jamestown. North Dakota Lt. Gov. Michelle Strinden, Jamestown Mayor Dwaine Heinrich and Stutsman County commissioners joined the ceremony, along with the Jamestown Area Chamber of Commerce, to recognize a project that has been one of the biggest public-infrastructure milestones in the area this spring.
The work changed the spillway, not the dam’s everyday role. Pipestem Dam still serves the same flood-reduction purpose it has carried since 1973, alongside Jamestown Dam, as part of the system built to protect Jamestown and the James River Basin. But the upgraded spillway now gives engineers a stronger emergency path for major snowmelt, heavy rain and other large runoff events. The Corps said the spillway is designed to pass up to 110,000 cubic feet per second, while the outlet structure can release up to 2,300 cfs.
That added protection matters because the old spillway carried a known erosion risk. The Corps evaluated Pipestem Dam in 2007 and classified it as a moderate-urgency dam. Engineers later pointed to the 2009 erosion failure risk at nearby Cottonwood Creek Dam as a warning sign, noting that similar erodible geology under Pipestem’s spillway could progressively wear away in an extreme flood and lead to a breach. The agency moved ahead before that kind of event could put downstream residents and infrastructure in danger.
The completed project cost about $250 million and used roughly 150,000 cubic yards of concrete, along with a labyrinth crest, stepped spillway chute and stilling basin designed to control water and reduce erosion during high-flow events. Barnard Construction Company, Inc. said the work included about 2 million cubic yards of soil excavation and backfill, 96,575 cubic yards of roller-compacted concrete, 26,760 cubic yards of soil cement and 20,575 cubic yards of cast-in-place concrete. The project also included a concrete terminal structure and other features intended to armor the spillway against erosion and handle emergency flows.
Construction began with a groundbreaking on May 25, 2023. Sen. John Hoeven said he helped secure more than $170 million for the project through the Corps’ fiscal 2021 and fiscal 2022 work plans. While some finishing work was still described as staged through the end of 2026, the ribbon cutting signaled a clear milestone for a dam that was built in 1971 and completed in 1973, with a maximum height of 107.5 feet and a length of about 4,000 feet. For Stutsman County, the upgrade was about more than engineering. It was a long-term investment in confidence that the system above Jamestown can still do its job when the river rises.
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