It's been done in Chicago, Boston, San Diego and San Francisco. The state of Connecticut passed a law requiring it whenever possible. And it's commonplace in Europe, Asia, Australia and Canada.
Burying transmission lines - even at voltages as high as 500 kilovolts - is an industry trend worldwide.
"Typically, they just get buried and left there," says Ian Hiskens, a professor of electrical engineering at UW-Madison. "No one really thinks about it too much."
Yet American Transmission Company adamantly opposes burying any part of the 345-kilovolt line it wants to build in Dane County. The company is proposing a line from West Middleton to Rockdale, at a cost of between $213 million and $250 million. It claims that burying even a portion of the line - the 18 miles along the Beltline from the West Middleton substation to Stoughton Road - could more than double the project's total cost, to $500 million.
ATC also says the technology for burying high-voltage lines is still unproven and could cause significant outage problems. It's only in the past few years that utilities in this country have buried lines above 69 kilovolts.
"There is not a significant operating history in the U.S.," says Patsy Baynard, ATC's general manager of construction for major projects. "It's an emerging technology."
But much of what the company alleges about underground lines - high cost, maintenance issues and environmental concerns - has been called into question. Last year, a group of Beltline business owners and local officials formed the Coalition for an Underground Alternative. The group says building a huge transmission line along the Beltline corridor could depress property values, hurt sensitive economic development projects and ruin the UW's Arboretum. And the group says ATC is misleading the public about the feasibility of undergrounding.
"They're just saying no because they can," asserts Harvey Temkin, a lawyer and spokesman for the coalition. "That's a little frustrating."
ATC officials have said the new transmission line could be in service for the next 100 years. Temkin says it's important for residents to decide now how they want the community to look for generations to come.
"Within five years, it's possible all [transmission lines] will be underground," says Temkin. "The country is moving in that direction. Do we want to be the last place that's just got these god-awful overhead lines?"
Last January, Brad Hutter flew to San Diego to attend an engineering conference. Hutter, the president of Mortenson Investment Group, wanted to learn why undergrounding wasn't an option for Madison. Instead, he came away believing that undergrounding "is technically viable and economically viable."
At the conference, Black & Veatch, a consulting firm that works on underground projects, gave a presentation on costs. The firm noted that, in the U.S., it typically costs $10 million-$13 million per mile to bury a 345-kilovolt line. In Europe, the cost for undergrounding lines drops to $6 million per mile. (An overhead line costs between $2 million and $6 million per mile.)
In an analysis submitted to the state Public Service Commission (PSC) last week, ATC said it would cost between $21 million and $28 million per mile to bury the cable along the Beltline. Ultimately, the PSC will decide what kind of line, if any, is built in Dane County.
ATC officials attribute the price difference to inflation and the rising costs of materials, particularly copper. And the company cautions against comparing projects in different parts of the world.
"It's hard to know what other utilities included in their projects," says Sarah Justus, an ATC spokeswoman.
Critics say the cost of undergrounding the line would be shared by 5 million electric consumers in Wisconsin and upper Michigan. At a meeting this July, Middleton Ald. Bill Hoeksema asked Mark Williamson, ATC's vice president of major projects, how much the monthly charge for ratepayers would be.
"He did some math and said, 70 cents a month," recalls Hoeksema. "It winds up being a small cost."
Last year, Middleton passed a resolution, sponsored by Hoeksema, recommending that the line be buried. The city is concerned about the line's impact on its multimillion-dollar Greenway Station development. "There are buildings being built there right now," says Hoeksema. "We think a line will be unsightly in the air."
But Justus notes there "are certainly still plenty of overhead transmission lines being built across the country." And she questions whether the PSC should make the state's other ratepayers cover the cost of undergrounding a line here: "At what point and under what standard is it acceptable for everyone to pay for Madison?"
ATC's biggest concern about burying the line is not cost, but maintenance. In its analysis for the PSC, the company said if an outage occurs, it could take anywhere from four weeks to six months to repair. Because the cable used is XLPE, which is manufactured primarily in Europe, ATC says it will have to fly in technicians and materials from overseas.
"We don't keep a large amount of underground cable lying around just in case," says Baynard. "There's nobody in this area who has expertise with an XLPE cable at this voltage."
The UW's Hiskens thinks that's nonsense: "There should be people here who are familiar with that cable."
And he doubts the line would need much maintenance, anyway. Overhead lines are subject to damage from lightning, wind, ice, even an out-of-control semi on the Beltline. But underground lines are not affected by any of that.
"Once a cable is buried, there are no maintenance issues at all," says Hiskens. "Really, the only issue is if some turkey digs it up." Even then, it can be a relatively easy fix. When a bulldozer accidentally pulled up a 400-kilovolt line in Sydney, Australia, says Hiskens, "they had it fixed within a week."
And if maintenance problems do develop, sensors buried with the line can pinpoint the breakdown "within a few meters," says Hiskens.
But Baynard says it's dangerous to rely on a technology that is still evolving. "New technology has a life cycle, and this life cycle is in the early phase," she says. "There are more failures and problems."
ATC also claims an overhead line is more environmentally friendly because it only requires a tower every 800 to 900 feet. "If we construct an underground line, we'd have a 4-foot-by-4-foot, concrete-encased trench the entire length," says Justus. "The disturbance to the ground would be much more significant."
Kevin McSweeney, director of the UW's Arboretum, is more concerned about the impact of an overhead line.
"We have 220 different species of resident and migrating birds that are using the Arboretum," he says. "Both bats and birds are quite vulnerable to being killed by flying into the lines." (Justus says ATC can "mark" the overhead lines to make them easier for birds to see and avoid.)
The Coalition for an Underground Alternative recently received a letter from a consultant who suggested that an overhead line could reduce property values by 14% or more. "Don't think for a second that owners aren't going to challenge their assessments," says Hutter. "What is that going to mean to how much property taxes are collected, and how will that affect the budget? It's going to be dramatic."
Hutter accuses ATC of simply throwing up roadblocks. "They're trying to make like this is voodoo technology," he says. "ATC is confident the general public does not understand electrical transmission. They're counting on the public not educating itself."