Bonneville Dam Fish Passage and Spillway Improvements

Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR
Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR, US
Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR
Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR, US
Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR
Bonneville Dam Fish Passage Viewing Area
Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR
Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR, US
Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR
Bonneville Dam Fish Passage and Spillway Improvements | Columbia River Gorge, OR, US
USACE Portland District
Columbia River Gorge, Oregon, USA

Designated a National Historic Landmark, Bonneville Dam was built at the height of the Great Depression by the U.S. Army Corps of Engineers (Corps). The dam lies about 40 miles east of Portland, Ore., in the Columbia River Gorge and has been a major source of hydropower since it was completed in 1937. The project spans the Washington-Oregon border, with a lock and powerhouse to the south (Oregon) a spillway in the middle, and a second powerhouse to the north (Washington).

Since 2007, HDR has supported the Corps with services related to key elements of the dam, including the spillway and stilling basin which operate when river flows exceed powerhouse capacity, or as a passage route for endangered juvenile salmonids. When hydrographic surveys revealed serious erosion and cavitation concerns, HDR prepared an alternatives analysis and report for the Corps to evaluate potential repairs and improvements, including those related to fish passage and total dissolved gas (TDG) at the site. 

Alternatives presented to the Corps include adjustable flow deflectors, spillway pier modifications, a spillwall and a forebay behavioral guidance structure. Each of these alternatives presented numerous challenges ranging from major structural, mechanical and durability complexities associated with an the adjustable flow deflector concept to the depth, length and overall geotechnical issues associated with a 100-foot-tall, 1500-foot-long spill wall. General operational, maintenance and safety issues were associated with each alternative. Through a collaborative design process, the HDR team was able to develop viable alternatives for each of the design concepts, and ultimately develop a sufficiently accurate cost estimate together with a well thought out constructability review to help the Portland District and regulatory agencies make informed decisions.