Clear Trees? Or Bury Power Lines?

In the wake of power outages caused by storm-toppled trees, United Illuminating suggested cutting back all greenery around power lines. Others have suggested another solution: Placing all power lines underground, out of harm’s way.

That’s an option — if you’re willing to pay for it, and wait.

Putting overhead power lines underground offers a number of advantages: Fewer power outages, more room for street trees to flourish, and a more aesthetically pleasing cityscape.

“Undergrounding” also has some drawbacks: Power outages, when they happen, are harder to fix, and it’s very expensive to put all the power lines below ground.

It can cost a million dollars per mile to put lines underground. That would mean it could cost over $700 million to bury New Haven’s overhead power lines.

Putting electricity lines underground is just prohibitively expensive, said Joseph Thomas, United Illuminating (UI) vice-president of electric system operations.

Others disagree. Some cities are going ahead with burying projects, despite the expense. Anaheim, California, and Concord, Massachusetts, are in the midst of overhead-to-underground conversions.

Their solution to the high cost? Do it slowly. Really slowly.

Concord, with a population less than 15 percent of New Haven’s, started burying power lines in the early ​‘90s, and won’t be done until about 2065.

Since 1990, Anaheim has spent $185 million to put its power lines underground, paid for by a 4 percent surcharge on the monthly electricity bills.

Read on for a deeper look into the challenges and opportunities involved in burying power lines.

What kind of power lines do we have now?

For both overhead or underground, power lines come in three varieties. ​“Transmission” lines carry high voltages from generation stations to electrical substations. Primary ​“distribution” lines take the power, at lower voltages, from there to transformers. Secondary distribution lines then take the power directly to customers.

New Haven already has a fair amount of underground electricity infrastructure, mostly downtown. Here’s the breakdown in New Haven, according to United Illuminating (UI) spokesman Ed Crowder: 

Overhead:
Transmission: 8.73 miles
Primary distribution: 233 miles
Secondary distribution: 503 miles
Total: 745 miles

Underground:
Transmission: 68 miles
Primary distribution: 181 miles
Secondary distribution: 68 miles
Total: 317 miles

What’s the deal with overhead power lines? Are they good or bad?

Among the pros: It’s a relatively straightforward system; it’s all out in the open and accessible for repair. The system is also easily modified and rerouted.

But, as with many systems, its advantages can also be disadvantages. The lines are accessible, but vulnerable. They’re all out in the open, but they’re not very attractive.

Overhead power lines are most vulnerable during storms, which can knock down branches or full trees that hit power lines and cause outages. During 2011’s Hurricane Irene, for instance, some parts of Connecticut went without power for more than a week.

Irene was the first of three huge storms that have pummeled the state in recent years. It was followed by Hurricane Sandy in 2012, and Winter Storm Nemo in 2013, each of which led to more power outages.

As a result, United Illuminating started looking at more aggressive tree trimming plans, to the dismay of some ratepayers in New Haven. As long as power lines are overhead, cities will have to balance the needs of the power grid with the needs of street trees.

Overhead power lines seem problematic. What do underground systems look like?

They look fairly invisible, since the power lines are hidden away underground. Take a look at the blocks around the Green, where all power lines are below ground.

Burying can be as simple as digging a ditch, taking the lines off the poles and laying them in the ground. That’s called ​“direct buried” power lines. The better, and more expensive, way to do it is to install a conduit system, so that the wires are protected underground.

Underground power lines don’t conflict with tree canopies, and they’re not vulnerable to storm-toppled branches, which means a more attractive and reliable power system.

Sounds great. Let’s go underground! 

Hold on — underground power lines aren’t perfect either. As with overhead lines, their advantages are accompanied by downsides. Here are a few:

• Tucking electricity cables out of sight also means it is harder to locate and fix problems when they happen. The power may go out less frequently, but when it does, it takes a longer time to fix. Thomas, the UI vice-president, said repair times can be four to six times longer with underground outages.

• While underground power lines are safe from trees, they’re more vulnerable to flooding. Thomas said underground cables might not be appropriate for coastal areas, for that reason.

• Remember that utility poles carry not just power lines, but phone lines, too. Those lines don’t matter for power outages, obviously. But if aesthetics are your concern, then you’ll have to bury them, too.

• Underground power lines might save tree canopies, but their installation can have an impact on tree roots. In order to avoid hitting tree roots, the power lines would have to be buried under the middle of the street, a significant and costly undertaking.

• In fact, the biggest drawback to ​“undergrounding” is the cost. It can cost a million dollars or more per mile to put power lines underground. Underground power lines also have to be thicker and more expensive than overheads. United Illuminating determined that it would cost $6 billion to put all its lines in Connecticut underground.

The city has about 750 miles of overhead power lines, which could mean a $750 million pricetag if it all were to go underground.

That expense would ultimately land on ratepayers’ monthly bills. Individual customers would have to pay to install new underground connections from their properties to the grid. That might cost about $6,000 for the average customer, said Thomas.

Oh. Forget it, then. Let’s just stick with overhead lines.

Well, wait. At least a couple of towns have figured out how to work around these problems.

Concord, Massachusetts, for example, is about halfway done with the task of burying its power lines, funded by a small surcharge on monthly electricity bills. Concord started the job in the early 1990s and will be done by about 2065, said David Wood, head of the town-run municipal company.

“It’s a very slow process. It’s a very expensive process,” Wood said.

He said customers pay a 1.5 percent surcharge on their power bills, which generates about $400,000 annually. Wood said Concord has to let the money accrue over a few years before it can afford to bury another section of power lines. Wood said Concord cuts some costs by combining power line burial with water and sewer work.

Concord does have power outages occasionally, but they can be quickly repaired, even underground, Wood said. That’s because his staff are trained specifically for work on underground lines: ​“Our guys are very efficient.”

A failed cable can be pulled out and replaced in about six hours, Wood said. ​“Unless you have a conduit failure, which isn’t likely, you don’t have to dig up the ground.”

But Concord is tiny compared to New Haven. Tell me about Anaheim.

Anaheim, a city with more than twice the population and area of New Haven, began its underground conversion at about the same time as Concord. Like Concord, it also owns its municipal power company.

Anaheim’s plan is financed by a 4 percent surcharge on monthly power bills. The city has so far spent $185 million on the project.

Dukku Lee, Anaheim’s general manager of public utilities, said the work is costing about $4 million per mile. He called the higher price ​“reflective of the cost of living and everything else here in southern California. Costs tend to be a little higher than other areas.”

Lee said Anaheim isn’t aiming to eliminate every last overhead power line in the city. It’s focusing on the ​“major arterials,” which offer the ​“biggest benefits,” he said. It’s the difference between working on a water main that serves thousands and an offshoot pipe that serves dozens, Lee said.

Anaheim is now about 60 percent done with the conversion of its major arterials, Lee said.

The city has a rebate program to help homeowners who want to bury the power lines from overhead lines to their houses.

Lee said outage repair times for the city’s underground system can be as little as three or four hours.

I noticed you said both Anaheim and Concord have their own power companies. Coincidence?

Good catch. Yes, both Concord and Anaheim have municipally operated electric companies, which probably helps streamline the undergrounding process.

Lee said that because Anaheim’s power utility is run as a municipal not-to-profit, Anaheim residents pay 10 percent less than their counterparts in surrounding towns, even after the 4 percent surcharge for the line-burying project.

If New Haven were to decide to bury power lines, it might need to do it as part of a regional effort, which could be complicated by tensions between the city and the suburbs.

“The starkly higher cost for underground transmission has tended to diminish support for this option when the burden of payment is realized,” PURA Chair Arthur House wrote in a Jan. 30 letter to state Sen. Martin Looney, who asked about burying power lines. ​“In addition, we have found that lower income ratepayers often resist the prospect of aggressively more costly electricity bills to pay for buried power lines in suburbs.”

Even spread out over decades, Anaheim and Concord are still shelling out a lot to bury their lines. Is it worth it?

Hard to say. Aesthetics aside, the calculation may come down to what you think the weather will be like for the next century.

Thomas, the UI vice-president, pointed out that before Irene, Connecticut went about 25 years without suffering a major storm. If the state is going to see another 25-year stretch like that, then it’s probably not worth it to pay millions to put the lines underground. Others argue that in an age of climate change, it’s not accident that we have seen three devastating storms in three years.

As it is, both UI and the states Public Utilities Regulatory Authority (PURA) have concluded that the numbers just don’t make sense. To prevent power outages, PURA’s strategy focuses not on burying power lines but on three other things, according to spokesman Dennis Schain: First, ​“hardening” the existing system, making it stronger and better at withstanding severe weather. Second, a ​“realistic approach” to trimming trees. And third, ​“distributed generation,” so that power doesn’t have to be transmitted so far.

This last focus includes the creation of ​“microgrids,” which UI’s Thomas described as small generation and distribution systems connecting essential municipal buildings, including hospitals. A microgrid would be a ​“parallel system,” fueled by natural gas, for instance, that could take over if the main grid goes down.

Huh. There really doesn’t seem to be an easy answer to all this. Got any other ideas?

Actually, yes. Here’s one last thought:

All these measures to protect power lines might not be as necessary as people think. Connecticut’s forest may already be adapting to more and more powerful storms, so that future storms will lead to fewer downed trees and fallen limbs.

That theory belongs to Chris Ozyck, an urban forester with New Haven’s Urban Resources Initiative. He said that because Connecticut had gone for decades before Irene without a major storm, lots of trees and limbs were primed to fall when the hurricane hit. But each successive storm has cleared out more dead or weak trees and limbs, leading to less damage with each succeeding storm, Ozyck said.

“Trees get pruned by mother nature,” Ozyck said. ​“We have sort of a resilient forest now after it’s been tested. I personally feel like we have time.”