If you know how to build power lines, logic would suggest you already know how to take them down when they’ve passed the end of their useful lives and are deenergized: simply reverse the order of the steps you used when the line was built.
You would be wrong.
That was the experience of one expert with the Bonneville Power Administration (BPA), who was recently charged with removing two 115-kV power lines that were no longer used and posed a safety risk to the public.
“Initially we thought it would be easy because there wasn’t a lot of design involved,” project manager Chad Hamel told TransmissionHub.
The lines were installed in the 1940s to provide power to factories and mills in the industrial district along the Portland, Ore., waterfront. They served only one customer when BPA acquired the second 115-kV line from Portland General Electric (NYSE:POR) in 1982, and when that customer closed its plant in 2002, the line became obsolete.
Since the lines had long ago been deenergized, right-of-way (ROW) maintenance ceased, and when it came time to remove the lines, they had become shrouded in greenery “so thick with ferns and trees and undergrowth that it was a challenge just finding the structures to begin with,” Hamel said.
Adding to the difficulty of the project was the lack of access roads.
“Usually when we have access roads, we can drive a boom truck right up to it, yank the poles out of the ground, and move on,” he said.
However, the terrain the lines traversed – including a Portland park that is considered an “urban wilderness” area – made constructing such access roads, as one would do when building a line, impractical.
“The difficulty of the terrain would have required us to cut in an awful lot of roads and we would have spent a lot of money and probably a lot of years mitigating the damage that we would have done,” he said. “In this case, it made more sense to get creative and figure out ways to get in and remove these [poles] with the smallest impact possible.”
One of the techniques BPA considered was using a helicopter to remove the poles, which would have resulted in minimal disturbance of the terrain. But there were other challenges that scotched that idea.
“Helicopter deconstruction would have been great; it would have been quick,” he said. “It would have been like helicopter logging.”
However, he added that “the poles were so old – 50 or 60 years old in some cases – we didn’t know whether we could safely lift them out of the ground with a helicopter and fly them over a park when the pole might break and fall.”
The removal project became a ground campaign as ground crews with chain saws went in on foot to demolish the old poles and remove them, essentially by hand.
“There were lots of ground crews who were hauling these things out in little chunks with powered wheel barrows or game carts,” Hamel said. “It was kind of going back in time for means and methods of construction. We couldn’t use the big, fancy tools; we had to use small stuff.”
Mats were used to prevent tire ruts and other measures helped the crew reduce its impact on the site, he added.
When a new line is built, ROW paths are cleared, towers are erected and conductor is strung in areas that are restricted to authorized personnel. When a line to be taken down runs through populated suburban areas and popular recreation spots, the activities of the line’s neighbors must be taken into consideration.
“Timing things with the school season, with the soccer field and all that, we even had to schedule our construction around that to make sure that we weren’t doing things when there were [a] bunch of kids present, so we got creative at times,” Hamel said.
While demolishing the deenergized transmission lines did not require obtaining ROW easements, Hamel soon learned that did not mean there would not be any challenges with local landowners. Those challenges took BPA into uncharted territory: returning existing easements to the property owners.
“The easement that we inherited with [the Keeler-Pennwalt] line said that, once the line was gone, the easement was gone as well,” he said. “We needed to know, ‘How do we do this? How do we give it back?’ That’s something we’re still figuring out, depending on how the easements were written up.”
More line removals are on BPA’s time horizon and each one is special in its own way, Hamel said.
“We’ve got one that’s out toward the coast … where we’d relocated this line in the ‘50s,” he said. “There are about a dozen structures still standing, but it’s in a coastal estuary so how do you get equipment out there in the mud and time it between the tides and everything? So, that one’s going to be kind of tricky and it’s going to be a completely different type of removal.”
He concluded: “If it was easy, the lines would have been removed already.”