Living Lab
7:00 am
Tue December 24, 2013

Tunneling a Cable to Martha's Vineyard, 30 Feet at a Time

Submarine Cable from Falmouth to Martha's Vineyard, by Brian Morris

Martha’s Vineyard gets electric power through a cable that crosses from the mainland to the island. The cable also supplies fiber-optic communications for things like cable TV and cell phone service. In recent years, the cable has failed numerous times, and now Nstar and Comcast are teaming up to install a new one. It’s a complex process that took two years to win approval from various town, state and Federal officials.

The cable, known as a submarine cable, originates in Falmouth at the corner of Surf Drive and Mill Road. Part of that intersection is cordoned off with chain link fencing and “Construction Area - Keep Out” signs. The site is a maze of generators, digging equipment, hard-hatted workers, and a large vehicle with its rear wheels suspended high in the air, facing downward toward the ground.

Nstar Project Manager Coleman Gary explains the complex process. “What we’re doing here is horizontally drilling a 2,900-foot hole from here out to a barge out in the Sound,” he said, “so that the cable can run under all the critical habitat that’s out here - the eelgrass, the clam beds, everything else - so it can go out without having to do any environmental impact at all.”

The permitting process for the project began back in 2011.

“Things have changed,” Gary said, “concern about the environment has changed over the years. the concern over the types of habitats that are out here have changed over the years. So this is in response to those concerns.”

The cable is six inches in diameter, and contains three wires and two fiber-optic cables, all inside a six-inch shell. A barge anchored in Vineyard Sound has a winch  that will pull the cable through a pipe from the shore out to the Sound. From there, said Gary, the cable will be laid across the bottom of Sound. “When the cable is installed, a barge will haul a plow across the bottom that’ll cut a slot and lay the cable in.”

The environmental impact of that cutting will be low, and the sand and currents will quickly erase any signs of disturbance. Burying the cable below the bottom, Gary says, will prevent the cable from moving during storms or being dragged by a boat anchor.

“Right now they’ve drilled out, at this point, 2,000 feet. We’re gonna be goin’ 2,900. But they’re out 2,000 feet - almost to the location of that barge out there, and they’re gettin’ ready to add the next section of pipe. It moves out at 30 feet per shot.”

The Falmouth drilling operation is expected to wrap up by the end of January, and the cable will be ready to be fed into the pipe in Falmouth by April. Gary’s team will repeat the process to bring the new cable back on shore on the Martha’s Vineyard side in Tisbury. He predicts the new cable will be fully installed and in service by May of 2014.

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