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Posted on Mar 13, 2015

Wanapum Reservoir headed back up next week

With repairs at Wanapum Dam nearly complete, a rising of the reservoir pool is expected to start next week.

At the Grant PUD meeting on Tuesday, staff presented an anticipated schedule to commissioners.

Staff expects construction to be completed on Monday and the water will begin to be raised on March 19, with approval from the utility’s federal regulator.

The pool will be raised at a rate of 3 feet per day. The pool will be raised to about 569 feet, said Chuck Allen, PUD spokesman. So it will take about 10 days to reach that target.

That is still 2.5 feet short of the dam’s normal maximum pool elevation. A caisson along a portion of the spillway will be removed later this spring and the reservoir will return to its normal full pool of 571.5 feet, according to the PUD.

As of Tuesday, 34 of the 35 steel anchor tendons that are being installed at the dam have been set.

The PUD lowered the reservoir about 26 feet about a year ago after a 65-foot long crack was discovered on one of 12 massive concrete base sections on the Wanapum Dam spillway.

After completing enough work to stabilize and reinforce the spillway, the utility began to raise the reservoir in November. It was raised by 17 feet, or to its minimum operating level of between 558 and 562 feet. Then, in February, much of the shoreline was reopened.

Once the pool reaches 569 feet, all boat launches, with the exception of those under construction, will be reopened to the public, said Jeff Grizzel, director of natural resources for the PUD.

“We will monitor the shoreline for a short period once the refill is complete to ensure there are no substantive safety or cultural resource concerns,” Grizzel wrote in an email. “If not, we plan to reopen the entire shoreline to public access.”


— Staff report