With More Storms And Older Trees, Utilities Get Aggressive On Trimming

May 6, 2015

When you’re a transmission arborist, you spend a lot of time in a helicopter, cruising over power-lines.

“So here’s an example of non-compliant vegetation,” says Kurt Nelson who does this job for Eversource. He indicates some young pines growing underneath the tall transmission towers. They aren’t high enough to endanger the lines… yet.

“That’ll be a target for us,” says Nelson.

Today Nelson is also out looking for unhealthy trees which, if they fell, would knock down the line down. Whenever he spots one the helicopter banks hard, circling back, so he can take a GPS point.

“You can see how many white-pines we have in the state, and when it comes to reliability, white pines are sort of public enemy number one,” he says. Because their needles increase the amount of snow that weighs them down in the winter “they’re typically the tree that is most prone to fail.”

There’s also just a lot of them.

Out of all the states in the union, New Hampshire is the one with the most tree cover. Those trees provide many benefits, but they also have the unfortunate tendency to knock down power lines.

"It’s amazing, since I started, the program has grown tremendously,” says Nelson, who has been on the job since 2008. “The amount of resources we have. It has changed tremendously, I think we’re doing about four times the work we did when I first started.”

A contract tree-crew removes limbs that are too close to power-lines in Hopkinton.
Credit Sam Evans-Brown / NHPR

In recent years New Hampshire utilities have become much more aggressive in cutting trees back before they become a problem. Some utilities are spending nearly double what they used to on tree-trimming, and they say it's making a difference, and resulting in fewer and shorter outages.

Declining Reliability

In the late nineties, New Hampshire’s Public Utilities Commission became concerned about an upward trend in the length and frequency of power outages. As the utilities began to move toward enhancing their trimming programs some major outage events hammered home the idea that encroaching trees were getting bad.

Michael Cannata was with the PUC during this push, but before that he worked for Eversource, and is now an independent consultant. He has spent a big chunk of his career – both as a regulator and after – on what he calls his tree crusade.

“I got into evaluation of storms, you know, what’s causing power outages,” he says. What he found was at the same time that the state's second-growth forest has started to reach maturity, the region has begun to see more big storms. These factors were coupled with a decline in forest health thanks to invasive pests, and cut-backs in the number of tree-trimming crews the utilities employ.

On top of all this, people just rely on electricity more.

“You know you could call it a perfect storm, but it’s all focusing on the trees… if you can address the trees – and there’s only two ways to do it that I know of: either you trim them or you bury the lines,” he says.

A couple of studies have found the cost of burying every power line in the state to be astronomical, so regulators have required power companies to get much more aggressive with the trees.

Most power lines are trimmed to a standard 8 feet to the side, and 15 feet above the lines. Some more important "backbone" lines are trimmed "ground-to-sky."
Credit Graphic: Connecticut Public Utilities Regulatory Authority

These days, the PUC requires utilities cut back trees near distribution lines every four years, and have standardized the zones that have to be cleared. Utilities actively look for unhealthy snags that need to be preemptively taken down. They’re also clearing the full width of rights-of-way that previously they let grow in.

“No Pitchforks and Torches”

In other states that have gone to what’s called enhanced tree-trimming – like Connecticut and Maryland – there was some pushback… citizens groups were formed, and blue-ribbon commissions came out with reports.

But in New Hampshire, apart from some scattered grumbling, there’s been little objection.

Recently, Eversource took down more than a dozen trees on Main Street in Hopkinton that had encroached on the power lines.

The response? “A couple of phone calls but no pitchforks and torches yet,” jokes Neal Cass, the town’s administrator. “The arborist with Asplundh talked about putting in dogwoods, which are a traditional tree that don’t grow as big and don’t affect the lines,” he concludes.

It could be the citizenry is taking this well because there’s less tolerance for power-outages. It could also be that a state law that requires the utilities to ask for a land-owner’s permission before trimming most trees helps ease tensions.

Whatever the reason, utility data suggests that since the enhanced trimming began outages are getting shorter and less frequent.

“Remember each storm is different, they’re like snow-flakes there’s no two the same, you just can’t say because you had a hurricane, it’s the same,” says Michael Cannata, “But they believe the outages are being mitigated.”

The Holy Grail?

But it is expensive work.

Liberty, Unitil and the New Hampshire Electric Coop each spend between $1.5 million and $5 million a year on trimming. Eversource – which owns by far the most of the state’s electric distribution network – trimming costs have risen from $12 million in 2009, to nearly $24 million last year.

At the same time, utilities are investing in other methods of improving power reliability: stronger poles and guy-wires, and more equipment that can automatically detect faults and reroute power.

And while (once the data is “normalized” to account for the weather) outages do seem to be getting shorter, it’s not clear what’s having the biggest effect.

“We’re throwing everything we have at reliability, without doing a complete cost-benefit analysis,” says Susan Chamberlain, the State’s consumer advocate.

But the simple fact remains that most power outages in New Hampshire come from trees. 

“That’s kind of the Holy Grail, did we improve by taking that tree down?” says Bob Allen, who’s in charge of trimming distribution lines for Eversource. “Our best knowledge of the situation is that tree was gonna fail – it was an outage waiting to happen – and therefore we took it down.”

And they’ll likely keep taking trees down, just as long as they keep growing up.

While it can't say how much of this is due to tree-trimming, Eversource says its comprehensive program aiming to reduce outages has been working.
Credit Eversource Reliability Enhancement Program 2014 Report