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Work to reinforce Priest Rapids Dam riverbank to start this winter

By Cheryl Schweizer, Columbia Basin Herald
Published: January 16, 2020, 7:28pm

EPHRATA — Work to add reinforcement to the right bank of the Columbia River at Priest Rapids Dam is scheduled to begin by late February or early March.

Ty Ehrman, managing director of power production for Grant County PUD, said the low bid was $33.4 million. The engineering estimate was $46.2 million.

The low bid was submitted by IMCO Construction of Ferndale. Utility district commissioners reviewed the contract at the regular meeting Jan. 14.

Ehrman said the engineers were surprised the bid was so much lower than the estimate. But the company has worked on PUD projects previously, Ehrman said, including construction of a PUD fish hatchery.

Utility district engineers had selected a location to dump construction debris, but dumping there required permission from federal agencies. Commissioner Judy Wilson asked if the PUD had received federal permission. Ehrman said it hadn’t, but that utility district officials have an alternative location. The original location would reduce the impact to the Wanapum village, and PUD officials hope federal agencies will grant permission to use the original site.

The project is designed to address an unlikely but possible situation, a big earthquake that could cause the bank to crumble. It would take an earthquake of magnitude 6 or higher on the Richter scale, but if it happened the ground could get very unstable, a phenomenon known as liquefaction.

If it were to happen, the entire right bank could crumble, which could take the right end of Priest Rapids Dam with it.

In order to keep that from happening, the bank will be excavated down to the bedrock, then a concrete dam will be built to replace the dirt. Even though it’s extensive work, it shouldn’t have any impact on Priest Rapids’ operation.

Crews will excavate about 226,000 cubic yards of dirt and rock, and the new structure will use about 66,000 yards of concrete.

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