McNary Dam

McNary Dam is a concrete run-of-the-river hydroelectric dam spanning the Columbia River between Umatilla County, Oregon and Benton County, Washington. It is a key component of the Columbia River Basin's extensive Federal Columbia River Power System, creating Lake Wallula and providing significant power generation, navigation, and flood control benefits. The dam is named for Charles L. McNary, a longtime U.S. Senator from Oregon.

History

The push for development on the mid-Columbia River gained momentum following the completion of Bonneville Dam and the authorization of the Grand Coulee Dam under the New Deal. Planning for the project, initially known as the Umatilla Rapids project, intensified during World War II to meet the region's soaring energy demands for aluminum production and other wartime industries. Authorized by the River and Harbor Act of 1945, construction began in 1947 under the supervision of the United States Army Corps of Engineers. The dam was dedicated in 1954, playing a crucial role in the postwar economic expansion of the Pacific Northwest, supporting industries from The Dalles to the Tri-Cities, Washington.

Design and construction

McNary Dam is a massive gravity-type structure, approximately 7,365 feet long and 183 feet high. Its design includes a spillway with 22 gates, a powerhouse, and a navigation lock. The primary construction material was mass-poured concrete, utilizing aggregate sourced from nearby areas. A major engineering challenge was constructing the cofferdams to divert the powerful flow of the Columbia River, allowing work to proceed in the dry. The single-lift navigation lock, one of the largest in the world at the time, measures 86 feet wide and 675 feet long, facilitating the passage of barges and river traffic between Portland and Lewiston, Idaho.

Operations and power generation

Operated by the United States Army Corps of Engineers, the dam's primary function is hydroelectric power generation. The powerhouse contains 14 Francis turbine units, with a total installed capacity of 980 megawatts. On average, it generates about 4.7 billion kilowatt-hours of electricity annually, which is marketed by the Bonneville Power Administration to utilities across the region, including Portland General Electric and numerous public utility districts. The dam's operations are closely coordinated with other major projects like John Day Dam and The Dalles Dam as part of the integrated Federal Columbia River Power System managed for peak efficiency and grid stability.

Environmental impact and fish passage

The dam's creation of Lake Wallula transformed the riverine ecosystem and presented significant barriers to anadromous fish like Chinook salmon and steelhead trout. To mitigate this, the dam features an extensive fish passage system, including a state-of-the-art juvenile fish bypass and collection facilities, as well as fish ladders for adult upstream migration. These operations are conducted in coordination with agencies like the National Marine Fisheries Service and the Washington Department of Fish and Wildlife. Ongoing efforts, guided by the Columbia Basin Fish Accords and the Endangered Species Act, focus on improving survival rates for species listed under the Endangered Species Act.

Navigation and recreation

The dam's navigation lock is a critical link in the Columbia-Snake Inland Waterway, enabling barge transport of agricultural products from Eastern Washington and Idaho, such as wheat and lentils, to deep-water ports. The reservoir, Lake Wallula, and surrounding lands managed by the United States Army Corps of Engineers provide numerous recreational opportunities. Popular activities include boating, fishing for walleye and smallmouth bass, and visiting parks like Hat Rock State Park and the McNary Wildlife Nature Area, which offers birdwatching for species such as American white pelicans.

Category:Dams in Oregon Category:Dams in Washington (state) Category:Buildings and structures in Umatilla County, Oregon Category:Benton County, Washington Category:Hydroelectric power plants in Washington (state) Category:Columbia River