PUD announces drawdown at Priest Rapids Dam

PRIEST RAPIDS DAM — Grant County PUD officials have lowered the reservoir behind Priest Rapids Dam and declared a non-failure emergency after test drilling revealed leaking in the spillway supports (also known as monoliths).

The situation at Priest Rapids is not like the 2014 incident at Wanapum Dam, the utility’s other hydroelectric facility, according to a PUD press release issued Wednesday night. In that case Wanapum Dam had a crack in a spillway monolith.

The Priest Rapids drawdown was done “out of an abundance of caution,” the press release said. “There is no threat to life or property.”

The reservoir will be lowered three to five feet, said Christine Pratt of the PUD’s public affairs department. That’s still within the dam’s normal operating range, and it will continue to generate electricity. “Basically, we’re still operating as normal,” Pratt explained.

“The investigation and drilling at Priest Rapids is precautionary work after completing the repair at Wanapum Dam in 2015,” the press release said. Water leaked into the test holes at Priest Rapids, which is “an indication something might not be right. We just don’t know,” Pratt said.

“The reservoir will remain at the lowered level at least until the inspection work is finished,” the press release said. “The Priest Rapids spillway monoliths are stable, but merit further investigation.”

Priest Rapids has 22 spillway monoliths; a monolith is “the expanse of concrete below each of the dam’s spill gates,” the press release said. “Crews will drill inspection holes downward from an internal passageway, called the grout gallery, that runs the length of the spillway.” The test results will be analyzed to determine if repairs are necessary.

Cheryl Schweizer can be reached via email at education@columbiabasinherald.com.