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Generators like new again at nation’s largest hydroelectric producer

Workers recently finished a decade-long overhaul project at Grand Coulee Dam in Washington. The largest power-generating complex in the U.S. has 33 hydroelectric generators that supply more than 20 billion kilowatt-hours of electricity to the region, enough to power more than 1.8 million homes.
Years of planning and preparation paid off recently when the last of three generators came back online at Grand Coulee Dam. 
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“The end of this project means we have three reliable 805 MW generators we can count on to support BPA’s loads and the greater electric grid. It’s hard to overstate how important Grand Coulee is to BPA’s mission, and these three generators are a big part of that.”

Jim Alders, BPA Project Representative

After nearly a decade of work, three massive power generators at Grand Coulee Dam in Washington are fully online and once again supplying carbon-free power to the Pacific Northwest. Located about 90 miles west of Spokane, Washington, the dam stretches more than 5,000 feet across the Columbia River.

Grand Coulee is the largest power-generating complex in the U.S. Its three power plants and 33 generators supply more than 20 billion kilowatt-hours of electricity each year to the Northwest, enough to power more than 1.8 million homes. The Bonneville Power Administration sells that energy at cost to power utilities in five states and works closely with the dam’s operator, the Bureau of Reclamation, to maintain “the workhorse of the Columbia River.”

“Grand Coulee is by far the largest single source of electrical energy that BPA markets, and it’s routinely where we hold excess generating capacity to back up the Pacific Northwest electric grid, so it’s important to keep the generators reliable,” said Jim Alders, the BPA project representative. “The generating units undergo major maintenance every three years, requiring outages lasting months. These relatively short-term maintenance projects improve the reliability of the machine, but don’t bring the unit back to like-new condition.”

Getting back to “like new” entails a complete overhaul, requiring the units to be offline for years, not just months.

“Over time, smaller issues that cause short outages become more complicated and need more and more manpower and money to address them,” said Alders. “This years-long, planned overhaul allowed us to work on many smaller issues more directly and all at once.”

The recently refurbished 805-megawatt hydroelectric generators are inside the dam complex’s largest power plant, the Nathaniel “Nat” Washington Power Plant, which was built from 1967 – 1975. It houses six generating units capable of producing more than 4,200 MW, about two-thirds of Grand Coulee’s total generating capability. 

Taking three of the generators offline to fully refurbish them is no small feat. It takes years of planning and preparation to overhaul an incredibly important part of the nation’s infrastructure. BPA and Reclamation began planning the project in 2008, and in 2013, workers began taking the units offline, working on one unit at a time . The first two units came back online in 2016 and 2019, with the final unit returning to service on Sept. 30, 2021.

While the generators have undergone overhauls in the past, this latest project focused on their turbines. Complete disassembly required the removal of 6.5 million pounds of steel from each unit.  With the steel removed, many components of the turbine were sandblasted, welded, ground, polished and then repainted before reassembly. 

Restoring the turbine mechanical components improves the overall condition of the machine and increases its reliability. As a result, the generating units are available when called upon to provide power and grid stability, allowing BPA to focus its investment strategy at other places in the system where it’s needed. 

“The end of this project means we have three reliable 805 MW generators we can count on to support BPA’s loads and the greater electric grid,” said Alders. “It’s hard to overstate how important Grand Coulee is to BPA’s mission, and these three generators are a big part of that.” 

Grand Coulee is one of 31 federal dams generating hydropower for the Federal Columbia River Power System, built from 1933 through 1975. Maintaining the FCRPS infrastructure is an ongoing process.

For this project, BPA invested $200 million to add another 30 years to the three Grand Coulee generators’ lifespans. Investing in regular maintenance, refurbishments and upgrades at all the dams ensures power continues to flow from the generators to homes and businesses throughout the region. These investments are even more significant as the region moves toward a carbon-free future.

In the next decade, BPA and Reclamation are planning major overhauls on generators in Grand Coulee’s two other powerhouses, as well as the remaining three generators in the Washington powerhouse. Those projects will be underway well in to the 2030s.

Planning is also underway to modernize generating units at McNary and Chief Joseph dams. Turbine replacements and generator rewinds are happening now on three Ice Harbor Dam generators. Similar work is planned over the next 20 years for Libby, Hungry Horse, John Day, The Dalles and Bonneville dams.

Careful preparation by the FCRPS asset management planning team – BPA, Reclamation and the U.S. Army Corps of Engineers – to maintain the dams’ powerhouses and generators, keeps the region supplied with reliable electricity. The investments in hydropower have allowed the agencies to continue generating and delivering energy even as the Northwest experiences devastating winter storms and record high temperatures.

A worker removes the hardware for the wicket gate system on one of three hydroelectric generators at Grand Coulee Dm. Six-and-a-half million pounds of steel was removed from each of the massive units before they were overhauled. Once removed, many turbine components were sandblasted, welded, ground, polished and then repainted before reassembly. Photo by Bureau of Reclamation

A worker removes the hardware for the wicket gate system on one of three hydroelectric generators at Grand Coulee Dam. Six-and-a-half million pounds of steel was removed from each of the massive units before they were overhauled. Once removed, many turbine components were sandblasted, welded, ground, polished and then repainted before reassembly. Photo by Bureau of Reclamation

The 2,000 ton Rahco crane—the only one of its kind in the world – was used to reinstall a refurbished rotor in a hydroelectric generator at Grand Coulee Dam. A recent project to refurbish turbine mechanical components in three 805 MW hydroelectric generators restored the units’ overall condition and increased their reliability. Photo by Bureau of Reclamation

The 2,000 ton Rahco crane — the only one of its kind in the world — was used to reinstall a refurbished rotor in a hydroelectric generator at Grand Coulee Dam. A recent project to refurbish turbine mechanical components in three 805 MW hydroelectric generators restored the units’ overall condition and increased their reliability. Photo by Bureau of Reclamation

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