Bury Our Electric Lines? Easy Question, Complicated Answer

From Scott Carlberg

“Why can’t we just bury the wires?” When it comes to our electric system it is a simple question with no simple answer. Energy Consumers of the Carolinas looks at some of the issues about undergrounding electric lines. This is a question that comes up following big storms – ice, hurricane, thunderstorms.

First some background, explained well in Popular Science magazine this June: “There are two methods used to toss out poles and taking utility cables underground. The cheapest method is called open trenching, where utility companies dig into the earth, laying down the string of utility networks as they go and backfilling the trenches later. This often requires rerouting traffic and other significant (albeit short term) changes to the movement of a community.

“In either case, the wires hanging above aren’t ready for life underground without some modifications, the most important of which is insulation. Electricity wires are, by their nature, very warm, as they’re channeling currents to and fro. In the open air, this heat can dissipate, but deep in the soil it can’t. That’s why utilities wrapped their underground wires in plastic and surround them with a conduit like oil to keep things from overheating.”

After Hurricane Michael. Trees can take down lines, which renew the question about “undergrounding.” (Image from Duke Energy Media Gallery)

“It’s a monumental task,’’ an expert told the Boston Globe this past spring: “It’s not just taking existing lines and putting them underground. It’s entirely new equipment, it’s digging up roads and all the environmental considerations with that. There are issues with trees. And once it’s all done, the connection to the customer’s house would no longer be made with a pole at the top of the house. It would be an entirely new system underground to every single home and business that gets service.’’

Another environmental questions is this from an international electrical engineering organization – IEEE: “Utilities have been slower to bury transmission because of the expense,” according to a Washington-based utility trade group. “Transmission lines operate at higher power levels than distribution lines and generate more heat, which is harder to dissipate underground.”

The big issue is cost, and how that gets paid. An opinion piece in the Raleigh News and Observer said it is the “$4.9 Billion Question.” Sources quote various costs to underground lines. A million dollars a miles is a normal minimum; several million a mile are even quoted. The grid has a lot of miles … “the U.S. power grid is made up of over 7,300 power plants, nearly 160,000 miles of high-voltage power lines, and millions of miles of low-voltage power lines and distribution transformers.” (Source-US EPA)

Undergrounding was analyzed in North Carolina in 2003. The report said, “Such an undertaking would cost approximately $41 billion, nearly six times the net book value of the Utilities’ current distribution assets, and would require approximately 25 years to complete. The ultimate impact of the capital costs alone on an average residential customer’s monthly electric bill would be an increase of more than 125%.” That was in 2003 dollars.

The financial capacity of the electric system owner matters. While people may think about big investor-owned utilities and suppose they have deep pockets, consider municipal-owned utilities. A city is already balancing needs for sewers, schools, roads, insurance, debt-load, salaries, benefits, and other civic needs.

Undergrounding is complex. Recently a professor published a look at the issue. He is in Florida, a place that knows storms. “When it comes to electricity, people turn their attention to the power lines overhead and wonder if their electricity service might be more secure if those lines were buried underground. But having studied this question for utilities and regulators, I can say the answer is not that straightforward. Burying power lines … is expensive, requires the involvement of many stakeholders and might not solve the problem at all.”

After Hurricane Florence. How would underground lines do in this kind of environment? (Image from Duke Energy Media Gallery)

What if undergrounding doesn’t help resiliency? Kury added, “Also, undergrounding power lines may make them more susceptible to damage from corrosive storm surge and flooding from rainfall or melting ice and snow. Areas with greater vulnerability to storm surge and flooding will confront systems that are less reliable (and at greater cost) as a result of undergrounding.”

So, some questions to ask when considering undergrounding our electric lines:

  • Money: How much will it cost? Where would it cost more or less to do? How will be be funded?
  • Customers: Will it positively impact some/most/all the customers? Who gets undergrounding and who does not? How come?
  • Reliability: Could an underground environment actually be harder on some lines? How does that impact reliability?
  • Maintenance: Are underground lines tougher or more expensive to maintain? Could it be harder to fix underground lines if there is a problem?
  • Looks: What are aesthetics worth above ground versus underground?

There are degrees of “hardening the system,” or, making it more resilient, too. Some may involve making poles more resistant to breaking (concrete, in some cases), pole location, raising some facilities, aggressive tree trimming and vegetation management, and similar measures. There are many possibilities along a continuum of solutions and costs.

In the end for the Carolinas, this is an easy question to ask, but not answer. We have widely diverse geographies – seashore to plains to mountains (and the difference in soil versus rock, right) – and a range of economic abilities of customers or governments to shoulder the cost (see our blog about energy poverty), and the differing conditions where the lines would be. Then there is the need to engage all stakeholders – who wants their yard or business right-of-way dug up first, or at all? (Give me service but put the line somewhere else!)

State-level regulatory bodies can be arbiters of the undergrounding concept and its issues, though they need a way to gauge the divergent desires, positives-and-negatives, and resources to make the complicated answer to this easy question understandable and sensible for customers.