JAMESTOWN, N.D. -- The U.S. Army Corps of Engineers Omaha District has completed the $250 million Pipestem Dam Spillway Modification Project, fulfilling a three-year commitment to residents of Jamestown, North Dakota, and communities downstream of the dam.
A ribbon-cutting ceremony was held May 19 to celebrate the milestone.
“I see it as an insurance policy under which I hope we never have a claim,” said Jamestown Mayor Dwayne Heinrich.
Pipestem was identified as having erodible geology with glacial till and sand over shale making up much of the earthen spillway structure, prompting the need for proactive modifications.
The state-owned Cottonwood Creek Dam near LaMoure, North Dakota, had similar geology when it experienced a near-total dam failure in 2009 after 10 days of spillway flow almost “unzipped” its earth-cut spillway.
“This project is a shining example of our Dam Safety Program mission in action,” said Col. Robert Newbauer, commander of the USACE Omaha District.
An on-site manufacturing plant produced 144,000 cubic yards of concrete for the labyrinth weir and stepped chute. These features are designed to dissipate water energy in a much safer way.
Contractors broke ground on the project in spring 2023 and were able to complete the project on time despite a major setback in 2024 when the right slope experienced a landslide. Project leaders implemented a design-build adjustment and constructed a specialty retaining wall to keep the project on track.
Contractors and USACE leadership praised the partnership among geologists, structural engineers, hydrologists and contractor partners.
“Partnership is easy when everything goes right,” said Bryce Armknecht, contractor project manager. “It's when things go wrong that true partnership comes out.”
The Pipestem Dam is estimated to have prevented more than $100 million in flood damage over its lifetime. The new terminal structure will help prevent spillway erosion from breaching the reservoir for decades to come.
“While no dam can eliminate all flood risk, this modification provides a significantly higher level of protection and security for the region,” Newbauer said.
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