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NW Fishletter #395, July 1, 2019

[7] Added Fish Passage, Efficiency Expected With New Turbine Design

Federal agencies say a turbine with a new design has been installed, tested, and is now operating at Ice Harbor Dam. In the works for two decades, it is expected to increase power generation at Unit 2 by 3-5 percent and improve survival of a small percentage of juvenile salmon and steelhead that go through the unit's turbines on their migration downstream.

"We're pretty hopeful about this design and what it might accomplish," Kieran Connolly, Bonneville Power Administration's vice president of generation and asset management, told NW Fishletter.

One of four lower Snake River dams, Ice Harbor is located near Burbank, Wash., and has three 90-MW units, three 111 MW units, and total capacity of 603 MW. The U.S. Army Corps of Engineers project was authorized in 1945, and the dam's first three generators began operating in 1961, with three additional units completed by 1976.

BPA is funding the $96-million replacement of two turbines in a contract with Voith Hydro, a multi-national corporation headquartered in Germany that helped design the turbines. A third replacement at Ice Harbor and turbines at McNary Dam may follow.

Corps spokesman Joseph Saxon said a new fixed-blade turbine was installed at Unit 2 in 2016 and has been undergoing a series of tests since then to ensure that it's up to operating standards. It was commissioned and began operating May 2. The two adjustable-blade models of the new turbine design are in the planning stages at Ice Harbor, he said. The Corps is now receiving components for Unit 3's new turbine, which are being assembled for installation, he said. The adjustable-blade turbines are more costly, but also more efficient than the fixed-blade turbine.

Connolly said the turbines were specifically designed to improve fish passage, but have the added benefit of being more efficient, which increases power production. "We have the happy coincidence that the two go hand-in-hand," he said.

Another large benefit to Bonneville is the reduced risk of lost generation, he said.

Connolly explained that Ice Harbor is at a "constrained" part of the Snake River, so having the units available and in service to make use of the water for generation is important to BPA. The new turbines will significantly reduce the risk of lost generation, he said.

The 3- to 5-percent increase in efficiency is also "meaningful," he said.

Saxon said the turbines needed replacing due to age, which presented an opportunity to improve design. The Corps anticipates that the new design will also reduce maintenance costs and oil leaks into the river, as they use greaseless bushings. The turbine runner is made from stainless steel, which better resists corrosion from the water forces compared with the carbon steel runners in the original turbines.

Saxon said the new design tries to resolve the problem of pressure that's created by the blade when generating power, and how that impacts fish.

The potential improvements to fish passage are based on a "scale model testing," according to a Corps fact sheet on the project.

"The improved hydraulic design of the new turbine runners was supported by more than 20 years of research, development and evaluation of the effects of turbine passage on juvenile salmon," Martin Ahmann, a Corps hydraulic engineer and project technical lead, said in a news release.

Connolly said that the new design also attempts to reduce turbulence, or the places in a turbine where fish and water get jostled around. "You want a nice laminar flow, where it moves slowly through," he said. Turbines use the force of the water to turn, so anything that can help the turbine move without big changes in pressure, or gaps where things can get impinged, will also be better for fish, he said.

Connolly said that while some elements of this design have been used in other turbines and tested at other hydroelectric dams, this is the first turbine with this specific design, developed by the Corps and Voith Hydro, with input from the BPA and NOAA Fisheries. The agencies don't yet know specific improvements in survival for juveniles that go through the turbines. "We have some hopes, but we'll be doing testing of the units put in place to verify what kind of results we're getting," he said. As explained in a 2016 comprehensive evaluation of the Federal Columbia River Power system, "Based on computer and physical models, the new runners are expected to improve survival of turbine-passed fish by reducing the magnitude of pressure change, the probability of blade strike, and turbulence within the turbine passageways."

Any improvements in fish passage rates will be among the small percentage of juvenile fish that still go through turbines. But with millions of juveniles traveling downstream every year, even small improvements can make a difference.

Young fish get past dams on their migration downstream through many routes, including through turbines, juvenile bypass systems, spillways and surface passage routes, or collected and transported by barge or truck downstream. "Operations and structural improvements have been tailored to the specific conditions and structure of each dam to reduce the portion of juvenile fish that pass through turbines," the FCRPS evaluation said. "Depending on location, time of year, and species, approximately 76 to 99 percent of juveniles use these non-turbine routes," it said.

Juvenile survival rates also vary by route, species, and flow conditions, with the lowest survival rates for fish that pass through turbines.

"We're pretty proud of the strides we've made to improve passage at the dams," Connolly said. "Whether it's the spillways, the turbines, or the bypass systems, we're meeting or beating the goals that were set years ago."

Fish passage was the main focus in this new design, but "because of both the efficiency gains and the lost generation risk, we're feeling pretty good about this project," Connolly added. "We did have to spend money to get it in place, but the design principles we're hoping to apply to McNary in work we have coming up, and in the future at John Day. Those benefits will propagate across multiple dams."

While some question spending money at Ice Harbor when it is undergoing a breaching analysis in the Columbia River System Operations environmental impact statement, Connolly said the effort to redesign and replace the turbines started two decades ago. "It was largely getting to the point where the work had been commissioned, and the dollars were in place," he said. -K.C. Mehaffey

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NW Fishletter is produced by NewsData LLC.
Publisher/Editor-in-Chief: Mark Ohrenschall, Editor: K.C. Mehaffey
Phone: (206) 285-4848 Fax: (206) 281-8035

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