WENATCHEE — The Chelan County PUD’s top-priority repair has the powerhouse floor of Rocky Reach Dam looking something like a highly specialized yard sale.
Turbine blades, bronze bushings the size of ottomans, boxes filled with jumbo-sized nuts and bolts and other, far larger dam components with names that make sense only to engineers and hydromechanics are spread out for inspection.
Off to the side, a stout, pipe-like stainless steel rod some 30 inches in diameter and 12 feet long lies on its side displaying a hairline crack that has halted four of the dam’s 11 generators, cut the PUD’s generating capacity by a quarter, and set in motion an all-hands-on-deck effort to get the units spinning again.
“This is the most significant equipment problem we’ve seen,” Dan Garrison, the PUD’s hydro operation director, said Thursday from the powerhouse floor.
Kirby Reinhart, maintenance superintendent for Rocky Reach and Lake Chelan dams agrees. “On a scale of one to 10, I’d say it was an 11.”
The cracked cylinder, called a “servo rod,” spun inside the C10 generator unit under 3 million pounds of force and moved up or down to deliver the hydraulic oil needed to adjust the angle of the turbine’s five blades.
It was the only one of the four Italian-designed units that was displaying severe symptoms of damage — tripping offline automatically, leaking oil and shedding metal shavings into a catch strainer. It was taken off line in March.
Since then crews have discovered a laundry list of defects with the unit, including cracks in other components. Had the rod broken apart during operation it could have damaged other equipment and potentially flooded the powerhouse, Reinhart said.
One of the other three units is beginning to show symptoms.
Late last month, PUD officials opted to take all four of them off line to protect workers from the possible dangers of a catastrophic failure, and the Columbia River from a potentially large oil spill.
Commissioners Oct. 21 approved a declaration of emergency to allow General Manager Steve Wright to quickly contract for repair services without putting the work out to bid.
“We want to move as quickly as possible,” Wright told commissioners. “That’s balanced against trying to use the emergency declaration as little as possible, because competitive bids are good governance.”
The affected units are the dam’s four biggest and hardest-working. They’ve been in service since the early 2000s and were intended to last 50 years. Their 3-year warranty expired in August 2005.
Very preliminary repair costs exceed $5 million. PUD officials say the repairs will not result in rate increases to customers, since financial measures are in place to offset these types of unexpected costs.
They were designed by Italian company Riva, which manufactured two of them before the company was purchased by Pennsylvania-based hydropower giant Voith Hydro. Voith manufactured the other two, based on the same design.
The hydraulic, adjustable turbine-blade design replaced a fixed “propeller-type” turbine originally used at the dam, Reinhart said.
The adjustable design is not unique to the industry and is proven to increase efficiency — 5 to 6 percent more electricity generation with the same amount of water.
It’s also designed so fish that enter the chamber containing the spinning turbine blades are more likely to be washed through than killed.
PUD officials say they’re negotiating with Voith but won’t say if the Pennsylvania company will pay for part of the repairs.
The crack appears along a seam around the rod’s circumference where a collar-like shoulder is welded on.
Reinhart says that dam crews together with experts at Voith suspect that the weld cracked because it had been machined down too thin. In fact, it’s nearly 12 times thinner than it should be.
Analysis and disassembly of the damaged C10 unit will continue through December. It could be completely repaired by August, Reinhart said.
Crews will work over the coming weeks on an interim fix that will get the other three units — C8, C9 and C11 — spinning again by late March.
They plan to weld the turbine blades in place at their steepest angle to reduce stress on the rest of the unit, Reinhart said.
They won’t be as efficient as originally designed, but will at least be functional until permanent repairs are finished by late 2017, according to current estimates.
“It’s going to be a challenge, because we had a pretty full plate before all this happened,” Reinhart said. “It makes us wonder how we’re going to get everything else done.”