WENATCHEE — A suspected design defect that could threaten the safety of Chelan County PUD employees and the Columbia River has sidelined four of Rocky Reach Dam’s 11 generating units, possibly until November 2016.
Chelan County PUD officials say estimates of the cost to repair the four units and lost revenue from reduced generation are still preliminary, but could exceed $5 million.
The affected units are among the dam’s largest and hardest working.
They altogether generate about one-quarter of the PUD’s total generation of 2,000 megawatts. Their down time is on top of a fifth unit at the dam that was already out of service for repairs, Hudson said.
“It’s a big deal, yeah,” said Kirk Hudson, managing director of generation and transmission for the utility. “That’s why this is almost an all-hands-on-deck effort.”
Hudson said officials are working now to determine what caused the defect and whether any responsibility lies with the Italian company, Riva, that designed the units, or the contractor Voith Hydro of York, Pennsylvania, which took over the overhaul contract on the units.
Crews in March detected that one of the four units — C10 — had a deep crack in a stainless steel rod that delivers oil, under pressure, to a motor that adjusts the angle of the turbine blades. Excess oil was detected around the generator shaft and metal shavings were found in a strainer, a PUD news release said.
The defective unit was rebuilt in August 2001 and had the second longest run time of the four, Hudson said. The three other units — C8, C9 and C11 — are of the same design.
They were taken out of service as a precaution, although one of the three was also showing signs of leaking oil, Hudson said. Crews feared that ongoing use could cause oil to spill into the river or safety hazards for employees.
“Our priorities are protecting human health and the environment,” Hudson said. “That’s really the driver of our action here.”
Hudson said all the units have received routine maintenance checks that meet with industry best practices.
Crews think they can put together an interim repair plan that could get one of the units back on line by February, and all four back in action by August 2014.
Crews would then take the units off line one by one to do permanent repairs. That could take until November 2016, Hudson said.
Officials will have a better estimate of the financial impact in a few weeks, Hudson said. The unexpected expense is not expected to result in a rate increase, he said.
The PUD has insurance to protect against mechanical defects and resulting revenue loss, Hudson said.
This time of year, when river flow is low, it’s not unusual for one or two units to sit idle at Rocky Reach Dam, the PUD’s largest dam, which is just north of Wenatchee on Highway 97A.