PUD commissioners discuss dam refurbishment

EPHRATA — Repairing and refurbishing the rotors at Priest Rapids Dam could require the purchase of a spare part, and that particular spare part would cost about $1.9 million to design and build.

The PUD is in the first year of a decade-long project to refurbish and upgrade the turbines and generators at Priest Rapids Dam. Utility district commissioners were updated on the project’s progress at the regular meeting Tuesday.

Utility district engineer Jeff Niehenke said the news was better than at the last update given to commissioners in March. “A lot of uncertainty, lot of unknowns was where we were,” he said.

Engineers chose to start with the rotor that had been worked the hardest – meaning the most starts and stops – in the dam’s 50-plus years. An important piece of the rotor got stuck during disassembly, there was damage in unexpected places and it was impossible to inspect the whole rotor.

The damage, small cracks in an unexpected place, turned out to be not as bad as expected, Niehenke said. “What caused them we don’t know.” More analysis will be needed to see how much longer the rotor can be expected to keep working. The inspection was completed using ultrasound, and the rest of it was in good condition, he said.

However, “we have some uncertainties with future units.” Because the engineers don’t know what’s happening with the rest of the generator-turbine units, PUD administrators want to buy a spare rotor, just in case.

Niehenke said the design phase for the rotor has already started, will cost about $270,000 and will take about three months. Construction will cost about $1.7 million and will take about nine months. It would be delivered disassembled, and on-site assembly would cost about $1.1 million.

In answer to a question from commissioner Tom Flint, Niehenke said any new rotors, if they are needed, would be built to the specifications of the rotors at Wanapum Dam.

“So if we repair ours we really have no certainty how many years we’re going to get out of them,” commissioner Larry Schaapman said.

“Exactly,” Niehenke said.

Flint asked if it would make more sense to plan on replacing all 10 rotors. Hydro director Kevin Marshall said in his opinion it would be better to wait, inspect the next two or three and make a decision then. Niehenke said there’s enough time in the refurbishment process to build new rotors without affecting the schedule.

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