Map illustration of USACE-owned and managed dams in Seattle District. The district’s inventory of dams has multiple purposes including flood risk management, hydropower, navigation, water supply, river flow augmentation for fish, fish passage and recreation.

Overhead photo of Albeni Falls Dam, in Idaho, looking upstream. Photo courtesy Craig Brengle.

Photo of Chief Joseph Dam, the second largest hydropower producing dam in the U.S. It is the largest hydropower producing dam operated by USACE. The single powerhouse is over a third of a mile long and holds 27 house-sized turbines. Alone, it produces enough power to supply the whole Seattle metropolitan area.

Photo of Howard A. Hanson Dam, a U.S. Army Corps of Engineers dam, located near the headwaters of the Green River in King County. The dam is an earth and rockfill structure with inclined core drain and filters. Outlet works on the left bank consist of an approach channel, an intake structure providing upstream control, a 19-foot diameter horseshoe concrete-lined tunnel, a stilling basin, and an auxiliary 48-inch diameter bypass pipe.

Illustration of U.S. Army Corps of Engineers dams and levee systems. A federally regulated dam is any artificial barrier between six and 25-feet high, storing at least 50 acre-feet of water. Structures below six feet are not considered dams if there is no life safety risk. Any structure 25 feet and over storing at least 15 acre-feet of water is a dam. There are 90,000 dams in the U.S. that meet this definition.

Aerial photo of Lake Washington Ship Canal and Hiram M. Chittenden Locks, owned and operated by the U.S. Army Corps of Engineers, Seattle District. The Chittenden Locks will launch an extended gate-closure schedule to facilitate demolition, concrete construction, and installation and the commissioning of the new miter gates. The first round of gate closures is scheduled to begin Oct. 16, 2023. (Courtesy photo)

Photo of Libby Dam, a USACE-owned and managed operating project in Libby, Montana. The operating project provides protection from floods, produces hydroelectric power, and manages natural and cultural resources and recreation, while contributing to irrigation and navigation operations downstream.

Photo of Mud Mountain Dam, located in Enumclaw, Washington. The project protects more than 400,000 homes and businesses along the White and Puyallup river valleys, between Buckley and Tacoma, Washington.

U.S. Army Corps of Engineers (USACE) Seattle District shoulders a critical responsibility: ensuring the safety and reliability of its network of dams.

The district owns and operates six civil works project dams, from concrete gravity behemoths like Libby Dam in Libby, Montana, to earth and rock fill embankments at Howard A. Hanson Dam, near Green River, King County, Washington. Each dam presents unique challenges, influenced by its age, design and the ever-changing ecological conditions of the Pacific Northwest.

A federally regulated dam is any artificial barrier between six and 25-feet high, storing at least 50 acre-feet of water. Structures below six feet are not defined as dams unless there is a life safety risk. Additionally, any structure 25 feet and over storing at least 15 acre-feet of water is a dam. There are 90,000 dams in the United States that meet the federal definition.

Seattle District’s inventory of dams have multiple purposes including flood risk management, hydropower, navigation, water supply, river flow augmentation for fish, fish passage and recreation. They are classified as “high hazard” per FEMA publication 333, because failure (an uncontrolled release of water) or mis‐operation can result in loss of life.

“One might think that in 21st century America, we’ve put an end to dam failures, but that’s not true,” said Seattle District’s Dam Safety Program Manager Richard Smith. “Dams continue to fail for numerous reasons and all too often with disastrous consequences. Lives are still being lost, and it’s our responsibility as good dam stewards to ensure our dams do not fail,” said Smith, who has coordinated the district dam safety program activities since 2012.

Smith’s comments highlight not only the importance of the dam safety program, but its existence as a testament to USACE’s commitment to safeguard communities and infrastructure from the potential devastation of dam failure.

The district’s dam safety program provides inspections, assessments, instrumentation, emergency action planning, training, public awareness and other services needed to accomplish its mission. Its purpose is to ensure all the dams and accessory structures are designed, constructed, and operated safely and effectively.

The program’s success hinges on a comprehensive risk-management approach that involves a continuous cycle of data collection, assessments, monitoring and evaluation.

“The Army Corps of Engineers has fully transitioned to a risk-management approach to dam safety,” said Smith. “This means that, in addition to ensuring our projects meet or exceed current design standards, we evaluate the probability of failure versus consequences (i.e. risk) to manage dam repair or maintenance, by directing funds where they will reduce the most risk. This approach was new to the Army Corps about 15 years ago. Improving and streamlining this risk assessment process is the future.”

The risk-management approach includes USACE engineers completing formal inspections and assessments, special inspections triggered by events (like earthquakes and high pools), or informal inspections (like briefings and emergency planning activities), to check concrete surfaces for cracks, assess erosion on earthen embankments, or evaluate the functionality of mechanical components.

In March 2025, the dam safety team inspected the small lock and its emergency closure project at Lake Washington Ship Canal and Hiram M. Chittenden Locks, Seattle, and together with the district’s Emergency Management and Water Management sections, the team continued partnering with the Federal Emergency Management Agency with their Collaborative Technical Assistance program, sharing flood inundation and emergency preparedness data on Howard A Hanson Dam, to support King County first responders and their dam-related emergency response. The dam safety experts recently completed its periodic inspection and assessment at Albeni Falls Dam, Idaho, April 28-May 13, 2025.

The dam safety program team (which includes input from the district’s Engineering, Operations, Construction and Contracting Divisions) executes extensive remediation projects to fix identified deficiencies. These range from concrete repairs, embankment stabilization, new instrumentation installation or developing and maintaining well-defined emergency action plans with surveillance and monitoring plans, emergency exercises and maintaining all related reports and material for each project in a current and effective condition.

By applying careful planning and communication, the district’s dam safety program team navigates the complexities of working with various stakeholders, including government agencies, environmental groups and the public.

The team routinely engages with local Tribal Nations, recognizing the importance of consulting with those whose lands and resources may be affected by dam operation. It also partners with the Emergency Response organizations (such as local sheriffs), the National Weather Service and local and state emergency management organizations for emergency planning, meeting annually (to coordinate or update emergency planning documents) and every five years (to execute tabletop exercises).

Committed to transparent communication with the public, USACE officials regularly communicate dam safety information to communities, and to address their concerns.

“Many of our communities owe their reduced flood risk to the presence of dams,” said Smith. “Without dams (like Howard A. Hanson and Mud Mountain, for example), the Green and White River valley systems would flood regularly, causing massive economic damage and endangering lives. The safety and continued operability of these projects is vital to the health and economic well-being of the region.”

The district’s dam safety program continues to evolve, incorporating the latest advancements in engineering and technology. Leveraging past successes and failures to reduce the risks of future failures and incidents, the program benefits from ongoing research and development, ensuring it remains at the forefront of dam safety practices.

Through meticulous monitoring, rigorous analysis and proactive maintenance, Seattle District’s Dam Safety Program holds back the flow, playing a vital role in protecting lives and property, while ensuring the safety and reliability of critical dam infrastructure for generations to come.

Click: https://www.usace.army.mil/Missions/Civil-Works/Dam-Safety-Program/ to learn more about USACE’s Dam Safety Program.

To learn more about the dams in your area, click: https://nid.sec.usace.army.mil/#/