Overview
McNary Dam is a concrete gravity run-of-the-river structure that spans the Columbia River, serving as a critical node in the Pacific Northwest's hydroelectric and navigation infrastructure. The facility is located at the border of Umatilla County, Oregon, and Benton County, Washington, situated 292 miles (470 km) upriver from the river's mouth. It is positioned approximately one mile (2 km) east of the town of Umatilla, Oregon, and 8 miles (13 km) north of Hermiston, Oregon. The dam is operated by the U.S. Army Corps of Engineers through its dedicated McNary Lock and Dam office.
Historical Context and Naming
The project was originally planned to be named Umatilla Dam, reflecting its proximity to the Oregon town. However, the Flood Control Act of 1945 officially renamed the structure in honor of Senator Charles L. McNary of Oregon. Senator McNary had died in February 1944, shortly before the legislative action that secured the dam's new moniker. The facility was commissioned in 1954, marking the beginning of its operational history on the Columbia River system.
Infrastructure and Functions
McNary Dam functions as a multi-purpose facility, primarily focused on power generation, navigation, and recreation. The structure is 1.4 miles (2.2 km) long, utilizing a concrete gravity design typical of large-scale run-of-the-river hydroelectric projects on the Columbia River. The dam contributes significantly to the regional energy grid with an installed capacity of 980 MW. In addition to electricity production, the dam supports the Columbia River's navigation channel, facilitating commercial barge traffic between the interior Pacific Northwest and the Pacific Ocean. The reservoir and surrounding lands also provide recreational opportunities, integrating energy infrastructure with local economic and leisure activities. The facility remains operational, continuing to serve the dual states of Oregon and Washington under the management of the U.S. Army Corps of Engineers.
History and Construction
The development of the McNary Dam began with early legislative efforts in 1931, aiming to harness the Columbia River for hydroelectric power and flood control. Initially, the structure was planned to be named Umatilla Dam, reflecting its proximity to Umatilla, Oregon. However, the Flood Control Act of 1945 officially renamed the dam in honor of Senator Charles L. McNary of Oregon, who passed away in February 1944. This legislative change solidified the project's identity and paved the way for construction.
Construction and Commissioning
Construction of the concrete gravity run-of-the-river dam commenced in 1947. The project spanned the Columbia River, connecting Umatilla County, Oregon, with Benton County, Washington. The dam is located 292 miles (470 km) upriver from the mouth of the Columbia, approximately one mile (2 km) east of Umatilla, Oregon, and eight miles (13 km) north of Hermiston, Oregon. The U.S. Army Corps of Engineers oversaw the construction, which concluded in 1954, marking the official commissioning of the facility.
| Year | Event |
|---|---|
| 1931 | Early legislative bills introduced for the dam's development. |
| 1944 | Senator Charles L. McNary dies in February. |
| 1945 | Flood Control Act renames the dam from Umatilla to McNary. |
| 1947 | Construction begins. |
| 1954 | Dam is commissioned. |
| 1957 | Full activation of the facility. |
Following its commissioning in 1954, the dam underwent a period of operational refinement, achieving full activation in 1957. This timeline reflects the strategic planning and execution by the U.S. Army Corps of Engineers, ensuring the dam's role in regional energy infrastructure and river management.
Engineering Specifications and Infrastructure
McNary Dam is a concrete gravity run-of-the-river structure spanning the Columbia River. The dam is 1.4 miles (2.2 km) in length. It connects Umatilla County, Oregon, with Benton County, Washington. The facility is located 292 miles (470 km) upriver from the mouth of the Columbia. The dam is situated a mile (2 km) east of Umatilla, Oregon, and 8 miles (13 km) north of Hermiston, Oregon. It is operated by the U.S. Army Corps of Engineers' McNary Lock and Dam office. The total installed capacity is 980 MW. The plant has been operational since 1954.
Structural and Hydraulic Specifications
The dam utilizes a concrete gravity design, relying on its mass to resist water pressure. As a run-of-the-river facility, it maintains a relatively low head compared to storage dams, optimizing flow for power generation and navigation. The structure spans the full width of the river channel at this location, creating a continuous barrier between the two states. The 2.2-km length accommodates the river's width and allows for integrated infrastructure, including powerhouses and navigation locks. The dam's position 470 km from the river mouth places it in a key mid-Columbia location for hydroelectric and transport logistics. The U.S. Army Corps of Engineers manages the hydraulic operations, balancing power output with flood control and navigation needs. The concrete construction ensures durability against the Columbia's variable flow regimes. No specific height or altitude data is provided in the current grounding. The spillway configuration is part of the gravity structure, though specific gate counts or types are not detailed in the source text. The facility's design prioritizes the efficient passage of water through the turbines while maintaining structural integrity under hydrostatic load.
Navigation Infrastructure
The dam includes a navigation lock system to facilitate river transport. The U.S. Army Corps of Engineers operates the McNary Lock and Dam office, which oversees both power generation and lock operations. The lock allows vessels to bypass the dam, connecting the lower Columbia River with upstream ports. The integration of the lock within the 1.4-mile structure minimizes the footprint while maintaining navigational efficiency. The lock system is critical for barge traffic moving goods between Oregon and Washington. The operation of the locks is coordinated with the hydroelectric output to manage water levels and flow rates. The facility supports commercial and recreational navigation along the Columbia River. The lock's specifications, including chamber dimensions or lift height, are not explicitly detailed in the provided grounding. The presence of the lock underscores the dam's dual role in energy production and regional transportation infrastructure. The U.S. Army Corps of Engineers maintains the lock mechanisms to ensure reliable passage for river traffic. The navigation infrastructure is an essential component of the Columbia River's multi-modal transport network.
| Parameter | Value |
|---|---|
| Entity Type | Hydroelectric Power Plant |
| Dam Type | Concrete Gravity Run-of-the-River |
| Length | 1.4 miles (2.2 km) |
| Capacity | 980 MW |
| River | Columbia River |
| Location | Umatilla County, OR / Benton County, WA |
| Distance from Mouth | 292 miles (470 km) |
| Operator | U.S. Army Corps of Engineers |
| Commissioned | 1954 |
| Status | Operational |
How does the hydroelectric generation system work?
McNary Dam operates as a concrete gravity run-of-the-river facility, utilizing the natural flow of the Columbia River to generate electricity. The primary power generation system consists of 14 main turbine-generator units. Each of these main turbines has a rated capacity of 70 MW, contributing to the dam’s total installed capacity of 980 MW. This configuration allows for a consistent output that can be adjusted based on river flow and downstream demand.
In addition to its standard output, the facility possesses an overload capacity of 1127 MW. This surplus capability enables the dam to respond to peak energy demands or grid fluctuations, providing flexibility to the regional power network operated by the U.S. Army Corps of Engineers. The run-of-the-river design means that the dam does not rely on a massive reservoir for storage but rather on the continuous volume of water passing through the Columbia River channel.
Station Service Turbines and Black Start Capability
A distinctive feature of McNary Dam’s engineering is its inclusion of unique 'station service' turbines. These auxiliary units are designed to make the dam largely self-sustaining. By generating power directly for the dam’s internal mechanical and electrical needs, these turbines reduce reliance on the external grid for basic operations. This self-sustaining characteristic is critical for the dam’s black start capability.
Black start capability refers to the ability of a power plant to restart its generators without external power from the grid. In the event of a regional blackout, the station service turbines can initiate the power generation process, allowing McNary Dam to restore power to the Columbia River system and surrounding areas. This resilience enhances the reliability of the hydropower infrastructure in the Pacific Northwest, ensuring that the facility can function independently during grid disturbances. The integration of these features underscores the strategic importance of McNary Dam within the broader Columbia River hydropower network.
Navigation and Fish Passage Systems
McNary Dam serves as a critical node in the Pacific Northwest navigation network, featuring a single navigation lock situated on the Washington side of the Columbia River. This lock facilitates the passage of river traffic between the Columbia and the Willamette River systems, connecting inland ports to the Pacific Ocean. The lock structure is designed to handle the significant elevation changes characteristic of the Columbia River's lower basin, providing a vital link for barge traffic carrying agricultural products, coal, and petroleum. The U.S. Army Corps of Engineers operates the McNary Lock and Dam office, which manages the daily scheduling and mechanical operations of the lock to ensure efficient transit for commercial vessels and recreational boats alike. The lock's dimensions and lift height are engineered to accommodate the standard sizes of barges used in the region, allowing for continuous flow of goods through the river system despite the dam's concrete gravity structure.
Fish Passage Systems
In addition to its navigation functions, McNary Dam incorporates sophisticated fish passage systems to mitigate the impact of the dam on anadromous fish populations, particularly salmon and steelhead. The primary fish passage mechanism consists of gravity-fed fish ladders, which allow fish to swim upstream through a series of pools that gradually elevate them over the dam's height. These ladders are designed to mimic natural river conditions, with controlled water velocities and resting pools to reduce fatigue for migrating fish. To supplement the gravity-fed ladders, the dam features three specialized "fishway" pumps. These pumps are critical for transporting juvenile fish downstream and, in some configurations, assisting adult fish during peak migration periods when water levels and flow rates vary significantly. The pump systems help to bypass the main dam structure, reducing the time and energy required for fish to navigate the barrier, thereby improving survival rates for species such as Chinook salmon, Coho salmon, and steelhead trout.
The integration of these fish passage systems reflects the dual mandate of the U.S. Army Corps of Engineers to balance hydroelectric power generation, navigation, and ecological preservation. The three fishway pumps are a distinctive feature of McNary Dam, addressing the specific challenges posed by the Columbia River's flow dynamics and the dam's location 292 miles upriver from the mouth of the Columbia. These systems are continuously monitored and adjusted to optimize fish passage efficiency, ensuring that the dam supports both economic activity and the health of the Columbia River's fishery resources. The effectiveness of these passage systems is regularly evaluated through biological studies and operational data, allowing for ongoing improvements to the design and management of the fish ladders and pump mechanisms.
Why it matters
McNary Dam serves as a critical node within the Federal Columbia River Power System (FCRPS), integrating hydroelectric generation, navigation, and ecological management across the Pacific Northwest. As a concrete gravity run-of-the-river structure spanning the Columbia River, the facility connects Umatilla County, Oregon, with Benton County, Washington, located 292 miles upriver from the river’s mouth. Its strategic position allows it to regulate flow and provide power to the regional grid while facilitating commercial barge traffic through its integrated lock system. The dam is operated by the U.S. Army Corps of Engineers' McNary Lock and Dam office, ensuring coordinated management of water resources for multiple stakeholders.
Formation of Lake Wallula and Regional Navigation
The construction of McNary Dam fundamentally altered the local geography by flooding the historic Umatilla Rapids, creating Lake Wallula. This reservoir formation smoothed the river’s profile, enabling consistent navigation for commercial vessels traveling between the Pacific Ocean and inland ports. The dam’s location, just one mile east of Umatilla, Oregon, and eight miles north of Hermiston, Oregon, places it at a key junction for regional transport and energy distribution. By mitigating the natural turbulence of the rapids, the facility supports a continuous waterway that enhances economic connectivity for agricultural and industrial shipments in the Columbia Basin.
Power Generation and Operational Role
With an installed capacity of 980 MW, McNary Dam contributes significantly to the hydropower output of the Columbia River Basin. Commissioned in 1954, the plant operates as a run-of-the-river facility, meaning its power generation is closely tied to seasonal water flows rather than large storage reservoirs. This operational model allows for flexible power output, responding to peak demand periods and complementing other energy sources in the regional mix. The U.S. Army Corps of Engineers manages the facility to balance energy production with flood control and water supply needs, reflecting the multi-purpose design principles of the FCRPS.
Ecological and Historical Significance
McNary Dam plays a vital role in wildlife habitat management, particularly for salmonid species that migrate through the Columbia River system. The creation of Lake Wallula and the regulation of river flows have influenced aquatic ecosystems, necessitating ongoing ecological monitoring and adaptive management strategies. Historically, the dam was originally planned to be named Umatilla Dam but was renamed in honor of Senator Charles L. McNary of Oregon, who died in February 1944, following the Flood Control Act of 1945. This renaming reflects the political and historical context of mid-20th-century infrastructure development in the Pacific Northwest, linking local engineering achievements with broader national policies.
What is the environmental and regional impact?
The construction of McNary Dam fundamentally altered the hydrology of the Columbia River, creating Lake Wallula, a significant reservoir that serves as a primary water storage and navigation asset for the Pacific Northwest. The dam spans the Columbia River, joining Umatilla County, Oregon, with Benton County, Washington, located 292 miles (470 km) upriver from the mouth of the Columbia. As a concrete gravity run-of-the-river dam, McNary Dam regulates water flow to support multiple regional functions, including hydroelectric power generation, navigation, and irrigation.
Reservoir Extent and Navigation
Lake Wallula extends significantly upstream from the dam structure. The reservoir reaches up the Columbia River toward the Hanford Site, a major historical and ongoing nuclear energy location in Washington state. Additionally, the lake extends up the Snake River as far as the Ice Harbor Dam, creating a continuous navigable waterway that connects the inland port systems of Idaho and Washington to the Pacific Ocean. This extensive reach facilitates commercial barge traffic, allowing agricultural and industrial goods to move efficiently between the interior West and coastal markets.
Irrigation and Agricultural Benefits
The regulation of water flow by McNary Dam provides incidental but critical irrigation benefits to the surrounding agricultural regions. The dam is located a mile (2 km) east of the town of Umatilla, Oregon, and 8 miles (13 km) north of Hermiston, Oregon. These communities and the broader Umatilla and Benton counties rely on the consistent water supply and flood control provided by the dam to support extensive crop production, particularly wheat, hay, and other staple crops of the Columbia Basin. The U.S. Army Corps of Engineers' McNary Lock and Dam office manages these water releases to balance power generation needs with agricultural demand.
Wildlife Habitat and Ecological Impact
The creation of Lake Wallula and the regulation of the Columbia and Snake Rivers have significantly impacted local wildlife habitats. The reservoir provides important aquatic habitats for various fish species, including salmon and steelhead, which migrate through the river system. The dam's lock and dam facilities help mitigate some of the navigational barriers for these anadromous fish, although the run-of-the-river nature of the dam also means that seasonal flow variations can influence spawning and rearing conditions. The surrounding areas, including the riparian zones along the Columbia and Snake Rivers, support diverse bird populations and other wildlife that depend on the stable water levels and vegetation patterns created by the reservoir.