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Hydropower Flows Here
BPA and partners surmount unique obstacles on Grand Coulee project
10/18/2013 12:00 AM
Working through fire, ice and an array of one-of-a-kind design and construction challenges, BPA and its partners complete a complex project to retire underground cables and build overhead transmission at Grand Coulee Dam.
Scorching 105-degree heat. Finger-numbing 20-degree cold. A grass fire that raged a stone’s throw away, forcing the evacuation of part of the town. Workers rappelling like mountaineers down the face of the nation’s largest dam.
Nobody said the $33 million Grand Coulee Line Replacement Project would be easy.
Ever been faced with a tough, high-stakes work project? BPA’s senior project manager Mark Korsness, senior construction manager Shantini Ratnathicam, project engineer Lance Lewis, construction inspector Len Schulmeister, their teams, contractors and partners at the Bureau of Reclamation certainly have.
Among the unusual demands and conditions they encountered on the road to completing the project in May:
One-of-a-kind design and construction challenges around the historic, contoured face of the second-largest concrete structure in the world.
A devilish web of minimum electrical clearances to observe in mapping and building a zigzag of 18 bundles of triple 500-kilovolt conductor attaching the Third Power Plant to the dam, then spanning the river to six new transmission towers.
Three towns, three counties and tribes to consult about the impacts of the project.
Electrical outages requiring two years of negotiation to mesh schedules with a dozen unrelated construction projects taking place simultaneously at the dam.
Twenty-seven miles of oil-filled underground copper cable to be depressurized, drained and extracted from tunnels deep within the dam.
All the while, the Columbia River rolling below – the ever-present partner, driver and supreme challenge.
How do you master a job of such complexity and come out the other side months ahead of schedule and $3 million under budget, with strong relationships and mutual respect intact?
Three succinct words, a professional mantra, from Korsness: “It’s the Team.” (And he always capitalizes the “T”.)
Although the line replacement plan formally began five years ago, in a larger sense, it was forged in fire three decades ago. In 1981, when the subterranean power cables were just a few years old, a fire broke out in one of the two tunnels. Entombed in the dam, the inferno burned for 10 hours before it could be extinguished.
That fire, believed to have been caused by an electrical fault, knocked 2,400 megawatts of power off the grid. It took more than a year to erect temporary overhead transmission lines spanning the river and two more years to replace the cables in the dam.
But it could have been even worse: The fire’s intensity, combined with the difficulty in safely accessing the crypt-like space, jeopardized the remaining set of transmission cables in the other tunnel. Had the fire reached them, it would have cost the region the full output of the third powerhouse – 4,215 megawatts. For comparison, that amount is nearly four times the power produced by the Northwest’s only nuclear plant, the Columbia Generating Station in Richland, Wash.
In light of that daunting history, there was a sense of urgency as the cables approached the end of their useful life. By then, the tunnels were hot, claustrophobic and “extremely creepy,” recalled spokeswoman Lynne Brougher of the Bureau of Reclamation, which owns and operates the dam.
“You have a really small space and you put these huge lines in there and they’re generating heat,” Brougher says. “Add the fact there were very few access points in and out of the (mile-long) tunnel, and workers felt challenged going in there. Toward the end we noticed bulges in the lines in the tunnel: The cables were actually expanding, and that’s not a good thing.”
A Reclamation report estimated that another tunnel fire could impair Grand Coulee’s ability to pass water for flood control and cost more than $200 million a year in lost generation.
In 2008, Reclamation asked BPA to design and construct the six sets of new 500-kilovolt transmission lines. This project would precede and support a much more vast construction plan: the 10-year, estimated $275 million project to overhaul all six generating units in Grand Coulee’s Third Power Plant, which provide 18 percent of the entire output of the 31-dam Federal Columbia River Power System.
After an environmental assessment and public comment process, an overhead design was chosen for the replacement of the cables inside the dam, making multiple line failures less likely, ensuring the safe and reliable transmission of power for the region.
But the preferred new configuration posed a host of its own challenges that required ongoing collaboration and great flexibility by BPA, Reclamation and contractor Wilson Construction. “We went to great lengths to minimize the potential impacts of this project on the local community, while at the same time making the necessary improvements to a facility that has the capability to power six cities the size of Seattle,” Korsness says.
Working with city officials, members of the public, tribes and stakeholders, BPA took steps to mitigate the impacts on the town of Coulee Dam and the surrounding area. The project team kept construction of new access roads to a minimum, and reimbursed the city for its costs associated with staging and activity around its historic town hall. And Wilson Construction repaired damage and repaved the city parking lot.
BPA designed three custom transmission towers across the Columbia River from Grand Coulee’s Third Power Plant, as well as three standard towers higher on the hill above the town of Coulee Dam, Wash.
BPA also removed two temporary 1983-vintage transmission towers from the riverside park at the Grand Coulee Dam Visitor Center and built new towers farther from local homes. Those were not the only Coulee Dam homes BPA took into account; an osprey’s nest was relocated from the old towers to a new riverside platform (and promptly deemed acceptable by the birds).
Perhaps the most difficult aspect of the project for the BPA team was the intricate overhead transmission design, which resembles nothing so much as the pattern of wires inside an extremely grand piano.
“It’s like asking someone to string a grand piano – with a cactus lying in the middle – and still maintain the system function,” Schulmeister says.
The first problem: Nothing was standard. Different models of transformers and faceted architecture on the back of Third Power Plant required custom designs and transmission attachments. Second problem: The face of the dam, where the lines ran next, presented an obstacle course, starting with a monumental overhanging lip and angled concrete surfaces crisscrossed by penstocks, an elevator shaft and footbridge.
“It was awkward because the design of the power plant wall, as well as the dam, were faceted surfaces,” says Reclamation senior engineer Jerry Robinson. “It was a challenge to find a flat surface to tie anything to.”
“Geography-wise, it was a nightmare,” says Schulmeister, who spent several 100-degree days hanging in a basket suspended off the lip of the dam to affirm the strength of each custom-made anchor as it was set into the concrete face.
Then the lines had to swoop across the Columbia River and go uphill to three 350-foot-tall custom-designed towers, three standard towers and a spreading yard, before reaching a substation and the BPA regional grid.
To prevent dangerous arcing, or uncontrolled discharge of current in unwelcome directions, high-voltage lines must maintain exact spacing and tension. They can’t be too close to each other, the ground, water or structures. The design had to take into account myriad angles and interrelationships among the 54 conductors and 10 overhead ground wires, as well as the effects of conditions such as wind, ice and heat. Conductor-to-ground clearances, phase-to-phase clearances, circuit-to-circuit clearances….
“My Dad went gray at a young age, and now I’m going gray too,” says project engineer Lance Lewis, 32. The Tuskegee University-trained mechanical engineer was only a year out of BPA’s student program in 2009 when he was thrown into the role of leading the transmission design teams and later ordering all the construction materials for the overhead phase of the project.
“Most people never get a chance in their career to build a 500 kV line – and Lance designed six of them,” says Korsness. “Go big or go home.”
Lewis credits the project’s success to relying on the expert support of the team, including BPA substation engineer James Kelly, transmission designer Len Custer, tower designers Juan Nuño and Dave Hesse, lead inspector Dan Holzer and BPA’s project partners. “I was learning as I was doing,” Lewis says. “It was quite the experience.
“We had a well-put together team – it almost turned into a family type thing. I don’t think I’ll ever see anything as complicated as that again in my career. I matured greatly, and I’m proud to say I was part of it.”
Korsness, a 23-year veteran senior project manager at BPA, likes big challenges – a mountaineer, he has summited five Northwest peaks higher than 10,000 feet. The most unusual project he has worked on at BPA was the seven-mile-long Puget Sound 69kV submarine cable installation to Lopez Island in the 1990s.
But this one ranks No. 2 on the complexity list.
“It did not go smoothly and there were lots of unforeseen obstacles,” Korsness says thoughtfully. “The team handled the unexpected stuff really well and still managed to finish under budget and ahead of schedule.”
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