PUD researching dam leak

EPHRATA — Grant County PUD officials expect to spend about another four weeks on exploratory drilling at Priest Rapids Dam, looking for the source of a possible leak in a spillway support (also called a monolith). The results will be analyzed to determine what repairs are needed, if any, said Rich Wallen of the PUD’s power supply department.

Utility district officials drilled test holes at Priest Rapids as a precautionary measure following the discovery of a crack in a spillway support at Wanapum Dam in 2014. Water leaked into the test holes, and PUD officials lowered the water behind the dam as a result. They also started drilling more test holes. “We’re working back toward the other bank right now, while also concurrently doing some drilling up out of the grout gallery,” Wallen said. (The grout gallery is designed to help relieve pressure on the dam structure and surrounding rock.)

Utility district engineers and administrators met with regional and national officials of the Federal Energy Regulatory Commission last week, Wallen said. “They added a couple items they would like for us to consider.”

Wallen updated PUD commissioners at the regular meeting Tuesday. In other business, Wallen said a newly refurbished turbine-generator unit had to be taken out of service and repaired.

The unit was the first in a 10-year project to upgrade all turbine-generator units at Priest Rapids, at a pace of about one unit per year. That follows the upgrade of all turbine-generator units at Wanapum Dam, which took about a decade.

“We returned (the unit) to service, and not long after we returned to service we started noticing some abnormalities,” Wallen explained. The lubrication system was damaged, which in turn damaged a bearing, which damaged the turbine shaft, he said. Commissioner Larry Schaapman asked if there was an early-warning system in place, but Wallen said no. “Our indication here was vibration, which is the wrong indication.”

In answer to a question from commissioner Tom Flint, Wallen said lint was discovered in a pipe that was inadequately cleaned, or not cleaned at all. In another case, a piece of equipment was accidentally dropped into the machinery.

Wallen said PUD officials are looking for ways to keep incidents like that from happening, whether during the refurbishment at Priest Rapids or maintenance at any other PUD facility.

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