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Burying electrical transmission lines not so simple

Arielle Wolfe brought her 6-year-old daughter, Hazel, to a New Hampshire Senate hearing in March to talk about power lines. Overhead electric transmission lines could scar New Hampshire’s landscape, the Derry resident said during public testimony on a bill that would have made putting the lines underground the state’s preference.

“It’s pretty simple,” Wolfe said. “Bury the lines, you can still get the power through the state.”

But it may not be so straightforward. The senate engaged in a lengthy debate on the burial bill last week – considering its effect on jobs, property values, future projects and costs, among other things – before ultimately voting to table the bill on a 16-8 vote.

Industry experts say it is technologically possible to run transmission lines underground; buried projects already exist around the world. But like overhead lines, underground lines have their own set of pros and cons that can be unique to each project. The biggest factor for all underground projects, they said, is the cost.

“The question is, is Bill Gates paying . . . because we can go underground no problem,” said George Gross, an electrical and computer engineering professor at the University of Illinois.

The concept of burying electrical lines in New Hampshire arose largely in response to the $1.4 billion Northern Pass project. It proposes to run 187 miles of electric transmission lines through the state – from Pittsburg to Deerfield – to bring 1,200 megawatts of Canadian hydropower to the region.

The project has agreed to bury 8 miles of line in the northern section of the route at an additional cost of $100 million. Northern Pass estimates the company would spend on average $3 million per mile on overhead and $15-20 million per mile of underground cable, spokeswoman Lauren Collins said.

Opponents of the proposal have said further burial will protect the state’s landscape and tourism industry from unsightly transmission towers.

Currently, the world’s longest underground project is a roughly 112-mile transmission line buried in Australia – 75-miles shorter than a completely buried Northern Pass. It’s more practical to run high-voltage direct current transmission lines along long distances, in part because they have fewer losses.

For those cables, no technical limitation exists on how far they can extend underground, but the cost can vary greatly depending on the terrain, said ABB Vice President of Business Development Roger Rosenqvist, in an email. ABB manufactures underground cable that has a capcity ratings up to about 1,000 megawatts.

For burial, several methods of trenching exist – from directly burying the line to encapsulating it underground in piping. The high-voltage cables – usually about 6 inches in diameter – need to be buried at least 3½ to 4 feet below the ground, Rosenqvist said.

Up above, workers keep a several-foot-wide right of way cleared of vegetation, trees and other external forces that can damage the buried line. “You don’t want roots and things impacting it,” said Kevin Jones, deputy director of the Institute for Energy and the Environment at Vermont Law School.

A major benefit of buried lines is that underground, they are largely protected from lightning strikes, falling tree branches, heavy ice storms and other forces that can take out overhead power lines, said Andrew Phillips of the Electric Power Research Institute. But if something does go wrong and there’s an outage, a buried line is less accessible and could take weeks to repair.

“You’re more likely to have things go wrong in an overhead line . . . but (it’s) much faster to restore,” Phillips said.

The digging process also could churn up new environmental issues, something Sen. Jim Rausch, a Derry Republican, brought up last week during debate on the burial bill.

“You can cut trees anywhere, can clear the land; when you are digging it opens up a whole other can of worms,” he said.

New Hampshire isn’t the only state grappling with sending lines underground.

In Vermont and New York, one company is pushing ahead with two separate plans to bring Canadian-generated power to the Northeast through completely buried transmission lines.

The $2.2 billion Champlain Hudson Power Express would carry 1,000 megawatts of power from Canada to New York City through 333 miles of cables buried both underwater and underground, said Transmission Developers Inc. CEO Donald Jessome.

About 60 percent of the project’s transmission line will be submarine, passing under Lake Champlain and parts of the Hudson River. The biggest advantage of going underwater is the lower price tag – it’s about 60 percent of the cost of burying under the land portions, Jessome said.

The underwater cable is more expensive, but it comes in longer reels – roughly 25 miles long, he said. Fitted on a boat, workers can bury long stretches of the submarine cable without any splicing.

Currently, the longest high-voltage submarine cable link runs roughly 360 miles under the North Sea, connecting Norway and the Netherlands, Rosenqvist said. In the U.S., submarine cables connect New Jersey, New York and Connecticut.

For a 1,000-megawatt underground project on land, a large flatbed truck could carry a reel of cable that is only about 2,000 to 2,500 feet long, Rosenqvist said. It means more splicing along the cable and vaults at each of those splice points, where any problems typically arise, Phillips said.

Jessome said it’s roughly $3.5 million for each marine mile versus $5 million per upland mile.

“Because of the shorter length of cable and the actual construction . . . it is just more labor intensive,” he said.

Jessome expects to get the final permits for the Champlain Hudson Power Express project this fall and, after 3½ years of construction, have the project up and running by late 2018. That all hinges on the funding; the company is in negotiations with multiple parties who would pay to use the line, Jessome said.

More recently, his company launched a similar $1.2 billion project: New England Clean Power Link. That would be a completely buried 150-mile transmission line running from Canada, under Lake Champlain and then underground for the final 50 miles to Ludlow, Vt.

The most important part of considering these projects is balance, he said.

“Can the market afford to bury transmission line? If it can, is that the most effective way?” he said. “If overhead is acceptable to the community, you should do it because it makes smart economic sense.”

(Allie Morris can be reached at 369-3307 or at amorris@cmonitor.com.)

New Hampshire's political process is broken. Don't be fooled by the double-speak of our state senators. They have shown, by their votes, that they want to subsidize Hydro-Quebec, Northeast Utilities and PSNH. It's a naked, dirty quid pro quo -- the developers and their associates give contributions, and senators give votes. Above-ground lines may be a bit cheaper for these developers than the responsible, majority regional approach of undergrounding. But nothing is free, and the corporate subsidy granted by our senators will be paid for with money taken out of the hides of NH people who lose value in their homes and businesses from the (avoidable) damage of the above-ground lines. At the end of the day, shame on us, the voters, if we do not do our job and kick these bums out.

NH ratepayers have been footing the bill for PSNH's incompetence for decades. To allow them yet another chance to fleece ratepayers, business and property owners, and those who choose NH as the world class destination it is for it's unique scenic beauty would be a travesty. We know from recent past experience that these huge towers are vulnerable and do fall down causing outages that last for weeks in the winter. Underground lines are far less vulnerable. I've never heard of a large scale underground transmission line ever having an extended outage. This is just about greed and excessive profit - not what's right or best for ratepayers in the long run. No one's rates will be noticeably lower if they trash our state with this and the many future lines being proposed.

whats the lifespan of the underground line versus the overhead??

Both of your posts are excellent. Moreover, this will do nothing to bring down electric bills and even if by chance it did bring them down $10 per month, who cares.

NH ratepayers have been footing the bill for PSNH's incompetence for decades. To allow them yet another chance to fleece ratepayers, business and property owners, and those who choose NH as the world class destination it is for it's unique scenic beauty would be a travesty. We know from recent past experience that these huge towers are vulnerable and do fall down causing outages that last for weeks in the winter. Underground lines are far less vulnerable. I've never heard of a large scale underground transmission line ever having an extended outage. This is just about greed and excessive profit - not what's right or best for ratepayers in the long run. No one's rates will be noticeably lower if they trash our state with this and the many future lines being proposed.

It would seem to me that repairing damaged lines would be a lot more simple by driving along I-93 to the affected site than getting to downed towers on top of Mt. Kinsman in the middle of winter - but then, I am no expert. What I do know is that projects are being buried all around us by corporate entities that are "in it" for the profit - so much profit, in fact, that they are donating lucrative sweeteners such as Environmental Trust Funds to host states. These projects will be employing and training local workers, and revenues will be flowing into state coffers long before Northern Pass gets out of court with all the law suits it seems to be courting. When will these senators realize that establishing solid, progressive policies that are in line with the overall public objectives is good business, setting a clear path for companies to follow. Overhead is not acceptable to NH, and burial has not deterred other firms, allowing business to move along more smoothly in our neighboring states.

apparently you know more about repairing damaged lines than the Electric Power Research Institute. Quote from the article "a buried line is less accessible and could take weeks to repair. "..

Common sense, really. I suppose it is true that underground is less accessible if they tried to bury it on that foolish route they've proposed through the mountains. But along the highway, where there would be no additional environmental impact, would seem to be optimal for access, And of course, the reliability issues would be minimized without vulnerable towers strung along our weather-prone mountains tops that are susceptible to massive failure and collapse from ice storms as we've seen in Quebec from time to time.

I think you are being obtuse here...less accessible is not a factor of where it is located on a map...but whether it is above or below ground.

Interesting title. Did anyone ever claim it was simple? Is it simple to install thousands of massive steel towers and string cables 15+ stories in the air? Not surprisingly, the cost figures provided by no. pass have been inflated beyond belief and they have refused to do a true comprehensive analysis. First, they claimed underground would cost 10 times as much as overhead. Now, they are claiming 5 - 6.7 times as much [3M vs 15 - 20M]. Is that if they try to bury it over mountain tops instead of beside highways and rail beds where the right of ways are pre-softened? The Champlain Hudson project says underground costs 5M per mile - not 15 - 20M. Someone is way off and it isn't hard to know who. The same company that was off by 14 BILLION on Seabrook and recently doubled the scrubber estimate. The same company who filed the fourth largest corporate bankruptcy in American history. If you looked at their resume, you wouldn't let them build you an outhouse but their unsupported claims are quoted as if they were true. Now, they would have us believe that digging 42" deep next to the highway is insurmountable and environmentally devastating but blasting and excavating thousands of foundations to the depth of 4 - 5 stories underground in order to set towers the height of 15+ story buildings on - through State and National Parks, neighborhoods and communities, zig-zag back and forth across I-93 like shoe laces - is the responsible thing to do. What are these people smoking? Why would we want such a monstrosity of vulnerable outdated technology when we could do the same smart thing that everyone else in our region is doing and using proven,modern, safe and reliable underground technology for such large scale transmission? Let your Senator know that you're not buying their baloney or washing it down with no. pass kool-aid. Tell them NH is just as good as CT and every other state around us and we deserve underground, too. If your Senator won't commit to burying large scale transmission lines, vote for one that will. It's our way of reminding them who works for who.

can someone point me to the reliable source that these towers need a 40-50 foot deep foundation?? Just for comparison, the Eiffel Tower at 1063 feet tall sits on a concrete base 2 meters thick.

Go to 3rd document down at http://northernpass.us/document-library.htm . You will see quotes of 35' deep for proposed Northern Pass structures. It's unlikely this depth figure is worst case scenario; more likely it's for the "average" tower of 90' height. Taller ones will need deeper foundations. Tower structures go as high as 155'. 40' or deeper foundations are not out of the question.

yep..you are right..it does say that. it also says that no foundation may be required for some..just burying 15 feet of the monopole...and this is only for monoploes..not for lattice structures. thanks for the info

NP will be built and all the NIMBY's will cry in their pillows every night

"This delay will continue indefinitely once litigation starts." Yep...I agree. Just like I-93 widening was delayed..years (decades?)..Maybe we should ask the young people that are leaving our state in droves what they think about NP. I mean, we do value their opinion right? Cant imagine a power line is high on their list of concerns,..maybe no jobs or highest in the nation rates....

As for Senator Rausch, he apparently drank the PSNH KoolAid and is talking nonsense. Trenching for direct lay buries the cable at about 42". Instead, Rausch would prefer some 2300 new overhead steel towers bisecting NH, the majority of which would require 30' x 30' concrete bases excavated to 45 FEET deep. And that is environmentally more sensitive, he would have you believe. Senator Rausch is retiring, a good chance to vote in someone not in PSNH's picket.

30' x 30' concrete bases excavated to 45 FEET ???? LOL...who is talking nonsense now???

What is needed here is for everyone to get a very large electrical bill this coming February..say about $1200. That should move the discussion along.

It is simple enough. At least five other projects in two neighboring states, including Hydro Quebec's own Hertel line, have found an economical way to go underground. Why can't Northern Pass? It's either sheer corporate greed and/or PSNH is trying to compensate for its other business failures and losses on the backs of New Hampshire residents via this chain of skyscrapers. It is simply not acceptable, and NH has been saying it's not acceptable for three and a half years now. This delay will continue indefinitely once litigation starts. Mr Jessome's TDI developers would not have dared to propose overhead in VT. Why should NH settle for less? To prop up a failing company? I don't think so. Demand modern technology. If your senator won't push for it, vote in someone else.

"NH has been saying it's not acceptable for three and a half years now...."...from the article.."The senate engaged in a lengthy debate on the burial bill last week – considering its effect on jobs, property values, future projects and costs, among other things – before ultimately voting to table the bill on a 16-8 vote."...It would appear that you are wrong.

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