Modernizing Post-war Era Infrastructure

Heavy lift braces future of McNary Lock and Dam

BY MARCY SANCHEZ

NORTHWESTERN DIVISION Walla Walla District

Rising 183 feet above the Columbia River streambed, the McNary Lock and Dam’s 14 70,000-kilowatt hydroelectric generator units can supply enough power for about 686,000 homes at full capacity.

Seventy years ago, the 1.4-mile-long, concrete gravity dam became the first project assigned to the U.S. Army Corps of Engineers’ newest district, the Walla Walla District.

There’s little doubt the role McNary Lock and Dam plays in the Pacific Northwest is significant. But no significant investments had been made to the project since its dedication, requiring much-needed modernization efforts. One recent effort replaced and modernized the project’s tailrace and intake cranes, which have been in service since 1953.

“The cranes were original to the McNary plant and had numerous safety and reliability issues,” said Samantha Handcox, project manager for the crane replacement project. “The updated design incorporated improved efficiencies and industry innovation while balancing the unique requirements of operating on a hydropower facility.”

Steel beams are prepared for placement on the U.S. Army Corps of Engineers Walla Walla District McNary Lock and Dam’s tailrace crane, also referred to as “Crane 4,” during construction of the new crane, which replaced a 70-year-old crane in 2023. The crane, along with the Intake Crane, or “Crane 5,” serves vital roles at the project, not only strengthening the project infrastructure but also supporting the region by enhancing hydropower production, fish passage through more efficient deployment of the fish screens, which redirect fish away from turbines, and protecting the lock and dam infrastructure itself through more efficient debris removal to ensure operations aren’t jeopardized.

U.S. ARMY COURTESY PHOTO

The cranes serve vital roles at the project, including the tailrace crane, or “Crane 4,” which deploys tailrace stop logs whenever a main unit needs dewatering for maintenance or repairs. The Intake Crane, or “Crane 5,” serves multiple purposes, which include deploying head gates and fish screens, and removing debris from the forebay.

The modernization effort aims to enhance hydropower production, improve safety, and boost operational efficiency. Upgrades, crucial for handling the heavy loads required for hydropower production and maintenance tasks, are designed to serve current and future operational needs.

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“The most significant change to the physical structure was completely redesigning the hoisting system, allowing removal of the “hammerhead” located at the top of the original crane. The new hoisting system also increases the efficiency of fish screen deployment and removal, reducing operational costs for that job,” said Handcox. “The main hoist capacity was increased by 10 tons to 150 tons, improving the ability to pull head gates and fish screens in and out of water without overloading the crane.”

Crane 5’s updated auxiliary hoist was also designed to place debris more easily into trailers during forebay clearing, added Handcox.

Additionally, the new cranes feature advanced hoist systems, state-of-the-art control mechanisms, and programmable logic controllers integrated with variable frequency drives. These technological improvements significantly enhance precision and operational reliability. The project also incorporates modern safety features to ensure the well-being of the workforce and surrounding environment.

“Prior to redesign, accessing the main hoist trolly and hammerhead machinery housing (at the crest of the crane) for maintenance, posed a fall hazard. Now all machinery is easily and safely accessible,” added Handcox.

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With the cranes expected to last upwards of 50 years, the $9.3 million project strengthens the infrastructure and supports the region by enhancing hydropower production; enhancing fish passage through more efficient fish screen deployment, redirecting fish away from turbines; and protecting the lock and dam infrastructure through more efficient debris removal, ensuring operations aren’t jeopardized.

The project, completed in November 2023, was not without challenges. During the replacement, staff noticed cracks in the concrete beams supporting the rails the crane trolleys on, requiring strengthening of all 48 concrete beams before the new crane was erected. The challenge demonstrated the value of USACE partnerships when design teams expected three-sided beam reinforcement, while the contractor provided an enlargement solution that surpassed the required load capacity and enabled them to finish two weeks early. Collaboration between the Walla Walla District, the Hydroelectric Design Center, and Structural Technology, an industry-leading contractor, was imperative to success.

More than 120 Walla Walla District employees work at the McNary project, serving as electricians, lock operators, painters, welders, riggers, utility workers, mechanics, biologists, environmental resource specialists, park rangers, heavy equipment operators, administrative staff, engineers, and maintenance workers. Together, they ensure the safe and continuous operation of the project, which sees over 5.5 million tons of commodities passing through the navigation lock each year. AE

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