McNary Dam

McNary Dam
Name	McNary Dam
Country	United States
Location	Umatilla County, Benton County
Purpose	Hydroelectricity, Navigation, Flood control, Recreation
Status	Operational
Operator	U.S. Army Corps of Engineers
Dam type	Concrete gravity and run-of-the-river
River	Columbia River
Length	7,365 ft
Height	183 ft
Opening	1954
Reservoir	Lake Wallula
Plant capacity	980 MW
Plant operator	U.S. Army Corps of Engineers

McNary Dam is a large hydroelectric, navigation, and multipurpose structure on the Columbia River that impounds Lake Wallula on the border between Umatilla County, Oregon and Benton County, Washington. Commissioned in the early 1950s, it was built by the U.S. Army Corps of Engineers as part of a coordinated series of Columbia River projects including Bonneville Dam, Grand Coulee Dam, and The Dalles Dam to provide electricity, improve inland navigation, and assist regional irrigation and flood control. The project bears the name of Charles L. McNary, a long-serving United States Senator from Oregon.

History

Planning for the dam emerged from federal initiatives such as the Columbia River Basin Project and post-World War II development programs involving the Tennessee Valley Authority-era ethos and coordination with agencies like the Bureau of Reclamation and the Bonneville Power Administration. Congressional hearings in the 1940s considered competing proposals from Oregon, Washington, and interests tied to the Hanford Site and Portland General Electric. Site selection near the confluence with the Umatilla River followed consultations with the Bonneville Power Administration and consultations with tribal governments including the Confederated Tribes of the Umatilla Indian Reservation. Construction began under contracts awarded to private firms under supervision by the U.S. Army Corps of Engineers; the project paralleled contemporaneous works like Grand Coulee and required coordination with wartime and Cold War infrastructure priorities. The dam was completed and began operations in 1954, entering service alongside the expansion of the Pacific Northwest electric grid.

Design and Construction

The dam is a concrete gravity structure with an integrated powerhouse and navigation lock, combining fixed and gated spillway sections similar in engineering approach to Bonneville Dam and The Dalles Dam. Design work incorporated input from firms experienced on projects such as Grand Coulee Dam and utilized techniques refined during construction of Hoover Dam and other major 20th-century works. Key features include a multiple-unit powerhouse containing Kaplan and Francis turbines supplied by manufacturers who also provided equipment for Teton Dam and Glen Canyon Dam. Construction required extensive cofferdams, diversion works, and large-scale concrete placement, with project management coordinated through the U.S. Army Corps of Engineers, Walla Walla District. River flow regulation involved collaboration with the Columbia Basin Project planners and regional utilities including Pacific Power and Seattle City Light.

Operations and Power Generation

Operated by the U.S. Army Corps of Engineers and integrated into the Bonneville Power Administration transmission system, the facility has an installed capacity near 980 MW delivered by multiple turbine-generator units. Generation scheduling responds to demands from urban load centers served by Portland General Electric, Tacoma Power, Bonneville Power Administration contracts, and industrial users such as facilities at the Hanford Site and regional aluminum smelters. The dam contributes to peaking, load-following, and ancillary services within the Northwest Power Pool and is coordinated with upstream reservoirs like Chief Joseph Dam and Priest Rapids Dam for flood control and seasonal flow shaping. Maintenance outages follow standards from federal hydraulic and electrical safety regulations and are planned to minimize impacts to navigation managed under the U.S. Army Corps of Engineers civil works mission.

Navigation and Locks

A primary objective was to create a navigable channel for river commerce between inland ports such as Pasco, Richland, Umatilla, and the seaport complex at Portland. The dam includes a single-lift navigation lock comparable in function to locks at Bonneville Dam and The Dalles Dam, accommodating barges and towboats that participate in grain export chains tied to facilities at Port of Portland and Port of Pasco. Lock operations are coordinated with the National Marine Fisheries Service for scheduling and with the U.S. Coast Guard for safety oversight. The lock supports commercial freight of commodities including wheat, fertilizer, and petroleum products that transit the Columbia-Snake River System.

Environmental Impact and Fish Passage

The creation of Lake Wallula and impoundment of the Columbia River altered habitat for anadromous species such as Pacific salmon and steelhead, affecting runs of Chinook salmon, sockeye salmon, coho salmon, and pink salmon in ways similar to impacts seen at Grand Coulee Dam and Priest Rapids Dam. Fish passage facilities, including surface collectors, bypass systems, and juvenile bypass channels, were installed and have been modified over time to reflect research by agencies like the National Marine Fisheries Service and the U.S. Fish and Wildlife Service. Mitigation and restoration efforts involve partnerships with tribal nations including the Confederated Tribes of the Umatilla Indian Reservation and programs under the Columbia River Basin Fish and Wildlife Program administered by the Bonneville Power Administration. Issues such as dissolved gas supersaturation, reservoir temperature stratification, and predation by nonnative species like smallmouth bass continue to be managed through adaptive measures informed by the Northwest Power and Conservation Council.

Recreation and Surrounding Area

The reservoir, Lake Wallula, and adjacent lands support recreation tied to parks and facilities managed by state agencies such as Washington State Parks and Oregon State Parks, as well as local authorities in Umatilla County and Benton County. Activities include boating, fishing for walleye, bass, and salmonids, hunting, camping, and birdwatching linked to migratory corridors used by species cataloged by the Audubon Society and state wildlife agencies. Nearby communities such as Irrigon, Umatilla, Kennewick, and Pasco derive economic and cultural ties to the dam through recreation, irrigation diversions connected to Columbia Basin Project canals, and historical associations with regional transportation corridors like the Oregon Trail and Union Pacific Railroad corridors.

Category:Dams on the Columbia River Category:Hydroelectric power plants in Oregon Category:Hydroelectric power plants in Washington (state)