Green Mountain Power plans to underground replacement to storm-damaged line

Vermont’s Green Mountain Power (GMP) plans to underground a replacement for a 34.5-kV subtransmission line that was washed away by Tropical Storm Irene, but the storm clouds have yet to abate.

The original line was partially supported by a power pole on an island in the Winooski River near the suburban Burlington, Vt., community of Winooski, but the island and the pole were both washed away by the storm.

“We looked at a variety of ways to bring it back, [including] rebuilding the pole and the island,” a GMP spokesperson told TransmissionHub on Sept. 12, but the Vermont Agency of Natural Resources nixed that plan.

In its preferred alternative the utility proposed colocating the replacement line with an existing 34.5-kV line that runs along a city street, then placing the line underground through the parking lot and yard of a condominium complex to return to the river, where it would connect with another part of its transmission system.

Placing lines underground is an alternative often sought by citizens concerned about the potential impacts of overhead lines, including concerns about the potential health impacts of electromagnetic fields (EMF). However, GMP’s proposal hasn’t allayed the concerns of some residents of the condominium complex, who are protesting the plan on the basis that the EMF would not be diminished by burying the line.

While experts agree that it is the distance from power lines, not shielding, that reduces the exposure to an electromagnetic field, the utility says the exposure would nonetheless be minimal.

“The EMF exposure at the nearest condo on an average line loading [day] would be about one milliGauss,” the spokesperson said. “Worst case if the line is fully loaded, sitting directly above the line, is going to be 200 milliGauss, which is really no different than parking yourself a foot in front of your microwave oven.”

The Gauss is the unit of measurement of a magnetic field.

Burying a power line in the town is not without precedent, the spokesperson said, noting, “The rest of the [existing] 34-kV line is buried right in the downtown area of the city.”

GMP has presented five alternate routes to the public in a series of public meetings, and has since presented the alternatives to the Vermont Public Service Board (PSB). The utility noted that its preferred route using existing structures for the overhead portion and undergrounding the rest would be the most cost-effective and least intrusive.

A decision by the PSB is pending.