$46 million Garrison Dam repairs target ‘high risk’ spillway that could threaten Bismarck

Major upgrades to North Dakota’s Garrison Dam are progressing after structural problems were discovered when the spillway was first used in 2011.

The U.S. Army Corps of Engineers awarded nearly $24 million for dredging and protective work around the spillway, expected to complete by 2028. Another $22 million was awarded last November for additional dredging, finishing in 2027.

The repairs became urgent after manhole covers dislodged during the 2011 flood release. Engineers found that larger flows could cause more covers to fail, potentially leading to spillway collapse and major damage to downstream communities including Bismarck.

While the probability is low, the Corps classifies the dam as “high risk” due to potentially devastating impacts. A broader $1.8 billion modification project is underway, with construction beginning in 2029. The dam controls Lake Sakakawea, the nation’s third-largest reservoir.