The Washington Department of Ecology is planning for $5.5 million in improvements to Zosel Dam, which is on the Okanogan River and used to help manage Osoyoos Lake water levels.
The work will result in the first major upgrades to the dam since 1987, when construction of the existing structure was completed. The improvements include a spillway gate replacement, new lifting mechanisms, an additional heated gate, new backup generator and electrical upgrades including energy-efficient lighting.
“This will increase the longevity of the dam and improve operations,” said Ria Berns, Water Resources Program manager for the Department of Ecology.
The work is still in the design stages, with the project due for completion by June 2025.
The International Joint Commission’s International Osoyoos Lake Board of Control oversees the operation of Zosel Dam to manage water levels in Osoyoos Lake, which crosses the British Columbia-Washington state border. The board will be reviewing the dam upgrade designs along with other agencies.
“I think that after 40 years, you’ve got to have some fine tuning and upgrades and a new look at the dam. I think that’s being accomplished,” said Kris Kauffman, a longtime board member who was involved in the construction in 1987.
Kauffman, also a water resources engineer for a private company called Water Rights Inc., said the board’s mandate is to ensure that the upcoming work doesn’t impact water flows and levels.
“We would be looking at hydraulic capacity, the ability to actually operate the dam under the current guidelines that we have, and the rule curve,” he said. “That includes the ability for access and ongoing maintenance of the dam.”
Current features of the dam include a control structure, auxiliary spillway and fish ladders. Credit: Washington Department of Ecology
Craig Jordan, dam safety engineer for the Department of Ecology, said the project is due to begin in the first quarter of 2025, which is generally a low-flow time on the river.
The schedule calls for work being done on one gate at a time, which will allow for full operation of the other three gates. “Once we get far enough along with the design, we’re going to be submitting and working with the board and verifying that this schedule works with them.”
The department hired an engineering consultant in 2020 to assess the dam's state and the consultant identified several improvements, Berns said.
Jordan explained that the existing gates were custom-made for the dam and they run on a hydraulic screw system. “We’ve had issues getting parts. If you strip out a nut, then you need to custom make a nut for it.”
The new system uses a cable and drum system which will be easier to maintain and allows for gates to be lifted faster than with the old screw mechanism. One gate on the dam also is heated, for use during the colder months when ice can impact operations. The improvements include adding a second heated gate.
Jordan added that the department is looking into additional fish passage measures at the dam. There are currently two fish ladders there, which were designed in the 1980s. “That’s something that we’re working with groups in the background, but it’s not part of this project. The next step here is what can we do to the dam to make it more fish passable.”
Updates on the upcoming infrastructure project will be posted to the Washington Department of Ecology web page.
Zosel Dam during the spring freshet, with the gates lifted. Credit: Washington Department of Ecology
Jeff Kart is executive editor of the Shared Waters IJC newsletter and a contractor to the US Section of the International Joint Commission in Washington, D.C.
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