Largest Dam Safety Project in USACE History. Tackling the problem of ageing dams.

At the end of 2023, contractors from ten construction and engineering firms gathered at the Garrison Dam in North Dakota for an industry day hosted by the US Army Corps of Engineers (USACE). This event marked the initial phase of planning for the most extensive dam safety modification project in USACE's history. The multi-year project aims to modernize the dam, built in the 1950s, to handle current and future hydrological conditions better. “The dam was not originally designed for the reservoir elevations and spillway releases expected today,” explained Andrew Barry, Chief of USACE Omaha District’s Dam Safety Production Centre.

Concerns about the spillway arose after record runoff in 2011 necessitated opening the dam’s spillway gates for the first time since 1955. The high water pressure damaged the spillway's subdrainage system and concrete chute. Barry emphasized that the modifications will focus on critical components, including the Tainter gates, abutments, areas behind the spillway chute walls, drainage pipes, chute slab, and the stilling basin. New seepage drains will also be installed near the dam’s powerhouse to enhance structural integrity. “Flooding can still occur, even when a dam performs as it was designed,” Barry noted, stressing the importance of understanding the risks associated with living downstream of a dam.

The industry day offered contractors insights into the project's scope and unique challenges. Jeff Greenwald, a planner and project manager with USACE Omaha District, highlighted two major challenges: North Dakota's shorter construction seasons due to severe winters and the need to coordinate construction around potential spillway operations during high runoff seasons. Contractors must plan for quick shutdowns before spillway activation. Col. Robert Newbauer, commander of the USACE Omaha District, provided opening remarks, emphasizing the project's significance and the collaborative efforts required to ensure its success.

Additionally, USACE researchers have developed advanced tools for predicting infrastructure failure risks, crucial for managing the approximately 740 dams and associated structures under their purview. Willie Brown, a research civil engineer at the US Army Engineer Research and Development Centre, highlighted the ageing infrastructure's challenges. The introduction of the RMC-TotalRisk software enhances risk assessments, offering a transparent and consistent methodology for evaluating dam safety nationwide. Haden Smith, a senior hydrologic engineer with the Risk Management Centre, noted that the tool can handle everything from simple to complex projects, significantly reducing study costs and improving the quality and speed of developing safety models.

Currently in the pre-construction engineering and design phase, the modification project is expected to begin around 2029 and take approximately six years. Garrison Dam, one of six USACE mainstem dams on the Upper Missouri River, is crucial for flood risk management, hydroelectric power, water supply, water quality, irrigation, recreation, navigation, and conservation efforts. The industry day marked a significant step in ensuring the safety and resilience of this vital infrastructure.

Enjoy below a video showcasing the Garrison Dam a civil engineering marvel !!!