Grant PUD begins final refilling of Wanapum Dam reservoir

Repairs to the Wanapum complex in Washington have reached a significant milestone as owner Grant County Public Utilities District has begin refilling the reservoir behind Wanapum Dam to its full capacity.

The utility dropped water levels behind Wanapum Dam by about 30 feet this past March, following the discovery of a 65-foot-long by 2-inch-wide horizontal crack discovered in the dam’s pier monolith No. 4 in February. reported that Grant PUD already raised the reservoir’s levels by about 17 feet in January amidst ongoing repair work to the dam, but the latest round of influx restore the reservoir to its pre-rehabilitation levels.

The refill began Monday and should take a maximum of two weeks to complete.

“This is the last major milestone for this project and the reservoir is anticipated to be fully restored and functional to pre-existing conditions for public access and utilization,” Grant PUD said in a release.

The refilling marks the culmination of a year that included a number of initiatives related both directly and indirectly to the dam repair project, including the construction of a new fish passage system, implementation of a new shoreline security strategy, preservation of archaeological resources, and improvements to a number of recreational sites.

“I want to thank our customers for their support and patience durinbg one of the greatest challenges we have faced as a utility,” Grand PUD general manager Tony Webb said. “We are fortunate to havea top-notch team of employees and contractors that have allowed us to reach this point ahead of schedule.”

The dam is also home to a 1,038-MW Wanapum hydroelectric plant. Grant PUD said it will continue generating power despite the drawdown.

The facility is a sister plant to the Priest Rapids project. Combined, the two have an output capacity of nearly 2,000 MW.

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Michael Harris formerly was Editor for

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