Bonneville Dam

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Bonneville Dam is a large hydroelectric and navigation project on the Columbia River, located about 40 miles east of Portland, Oregon, where the river forms the border between Oregon and Washington. It spans the Columbia in the Columbia River Gorge and was built by the U.S. Army Corps of Engineers.

The dam is a set of run-of-the-river structures with two powerhouses and a spillway. It also has locks so ships and barges can travel upriver. Behind the dam lies Lake Bonneville, the reservoir created by the dam. The project is operated by the U.S. Army Corps of Engineers and its electricity is marketed by the Bonneville Power Administration.

Construction began in the 1930s: the first powerhouse opened in 1937 and the associated lock and spillway were completed soon after. A second powerhouse and dam structure were added much later, opening in 1981 after work began in 1974. The project was funded in part to provide jobs during the Great Depression and to promote flood control, navigation, and electricity. The dam’s name honors Captain Benjamin Bonneville, an early explorer of the region.

Bonneville Dam is 171 feet tall and about 2,690 feet long. The spillway is gate-controlled, and the dam creates a capacity of about 537,000 acre-feet of water in Lake Bonneville. The power plants together have 20 turbines and an installed capacity of about 1,242 megawatts, with annual generation around 4,466 gigawatt-hours (roughly enough electricity for about 500,000 homes).

There is a history of river navigation accompanying the dam. The original navigation lock opened in 1938 and was once the highest single lift in the world, at 60 feet. A newer lock on the Oregon shore began operating in 1993, and the old lock remains but is no longer used for traffic.

The Bonneville area is also important for wildlife and tourism. The dam has fish ladders to help salmon and steelhead reach their upstream spawning grounds. The nearby Bonneville Fish Hatchery is a major attraction. California sea lions often gather around the dam during salmon runs, and sturgeon continue to spawn in the lower river below the dam.

The Bonneville Dam Historic District was designated a National Historic Landmark in 1987, reflecting its significance in engineering, history, and regional development.