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Posted on Nov 24, 2014

Wanapum Reservoir headed back up

Nearly 10 months after the pool behind the Wanapum Dam was lowered and the shoreline along the reservoir was closed, Grant PUD announced Tuesday it will begin raising the reservoir before the end of the month.

PUD officials anticipate the reservoir will begin to refill sometime between Nov. 24 and Dec. 11, said Chuck Allen, PUD spokesman. It will be a gradual rising of the pool that likely will include “a few feet” a day until 17 feet is reached, Allen said.

The reservoir will remain at that level until the repairs to Wanapum Dam are finished, Allen said.

The partial refill will take six to 18 days to reach the target elevation.

The 17-foot rise still falls short of a full reservoir increase of 26 to 30 feet, but it’s expected to be enough to protect the exposed cultural sites, reopen some boat launches and render the dam’s fish ladders usable without the current low-water modifications in place, said Thomas Stredwick, PUD spokesman, to the Wenatchee World.

Maximum elevation for the reservoir is 571.5 feet. The reservoir is not expected to be at full levels until the start of the recreation season, which is around early May, Allen said.

“The fact that we are seeing the river level increase less than a year after we found an unprecedented fracture in our spillway is nothing short of incredible,” said Bob Bernd, chairman of the board of commissioners.

The reservoir was lowered by 26 to 30 feet in early March after divers discovered a 65-foot crack across one of the spillway’s 12 concrete base sections. The 38-mile stretch of shoreline from above Wanapum Dam to below Rock Island Dam was closed in early March as a precaution for public safety and to protect culturally sensitive sites.

While the reservoir rises, the Wanapum shoreline will remain closed and shoreline patrols will continue until officials have a chance to evaluate which areas can be reopened, Allen said.

To date, 13 steel anchor tendons and four anchor bars have been installed at the dam, and 83 monitoring drains have been drilled in the spillway. Costs to fix the dam are expected to reach $69 million.

Crews are expected to complete by next week the dredging of the boat channel at Crescent Bar as well as the extension of a boat ramp there, Allen said.