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Assessment Finds Grant PUD Dam is Suitable for Safe and Continued Operation

Priest Rapids Dam in Washington State is “suitable for safe and continued operation,” according to its comprehensive safety assessment, Grant PUD commissioners recently learned.

Carried out by an independent contractor, the assessment is required by the Federal Energy Regulatory Commission, the same agency that oversees Grant PUD’s commitment to dam safety. The federal agency also issues the utility’s license to operate both Priest Rapids and Wanapum dams.

A FERC dam-safety engineer determined no safety conditions are present that require immediate remedial action and concluded that dam personnel are aware of future projects and analyses needed to keep the dam safe.

“Most of it was ‘Keep doing what you’re doing,’” Grant PUD Chief Dam Safety Engineer Zach Ruby told commissioners.

FERC dam-safety inspections occur annually at Grant PUD’s Priest Rapids and Wanapum dams. Inspections by independent consultants occur every five years at each dam, alternating between “comprehensive assessments” and less-detailed “periodic” inspections. Wanapum Dam, about 22 miles up the Columbia River from Priest, will receive its detailed inspection in 2029, Ruby said.

 Projects identified at Priest that are already on the dam’s “to-do” list include:

  • Embankment work: On the dam’s Yakima County side, Grant PUD last year completed a new roller-compacted concrete embankment parallel to most of the existing earthen embankment to increase seismic strength. A small portion of that embankment that was not reinforced with concrete will now be reanalyzed to show its risk of failure in an earthquake is low, Ruby said. An embankment is the usually earthen-and-gravel extension that connects the concrete powerhouse and spillway to the shoreline.
  • Anchoring: A project to anchor the dam’s spillway more securely to bedrock is planned in 2026 to repair a disbonded joint in the concrete.

Other medium-term projects will also be carried out to ensure the dam’s continued stability, he said, as well as embankment work and other projects at Wanapum Dam.

Grant PUD’s dam-safety personnel will be back at the commission in the coming weeks to seek approval for contracts to begin exploratory drilling and review the soon-to-be-complete seismic risk analysis of the earthen embankment on the Grant County side of Wanapum Dam.

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