Vineyard Wind is seeking approval from the Edgartown conservation commission to run two export cables off the coast of Chappaquiddick as part of the wind farm it intends to build about 15 miles south of the Vineyard. The cables are meant to transfer electricity generated from 84 wind turbines to a landfall point in Barnstable, where it will be channeled into the electric grid. Vineyard Wind representatives came before the commission on May 22 to present an overview of their plans. The commission was scheduled to reconvene on the matter on June 12 to further deliberate, and possibly take a vote.
The cables have already been approved by the state Energy Facilities Siting Board and by the Martha’s Vineyard Commission.
Holly Carlson Johnston, a senior consultant at Epsilon Associates, an environmental consulting firm working on behalf of Vineyard Wind, told the commission that depending on the composition and topography of the seabed and the vigor of currents, the cables will stretch between 12.4 and 13.7 miles under the Muskeget Channel. A corridor from 810 to 1,000 meters wide has been mapped for the cables, she said, to be sited based upon the most suitable seabed conditions. Once their paths are sited, she said, the two cables will be spaced about 330 feet apart, and at their closest, will be about one mile off the Chappaquiddick shore.
“The cables themselves are 10 inches in diameter,” she said. They will be buried at a “target depth” of five to eight feet by an apparatus called a jet plow.
“A jet plow is essentially a piece of equipment that sits on the seafloor and has a string of high-pressure water nozzles that fluidize a very narrow swath of the seabed,” she said.
A jet plow rests on skids on the seafloor, she noted. It will cut “about one meter wide for each of the two cables,” she said. This requires only one pass, she said, because the cable drops into the trench and sediment settles onto it and buries it.
She estimated the cable would be laid at about 100 meters per hour, and from Wasque Point to Cape Pogue, the work should be done in just over a week.
“Vineyard Wind’s absolute priority is to achieve burial and have that burial be contained,” she said. “We will be performing post-construction geophysical surveys both to verify initial burial of the cables, and to verify that they remain buried.”
If seabed is encountered that’s unsuitable for burial — too rocky, for example — Johnston said a “very conservative” plan in a “worst-case scenario” would be to employ concrete mattresses or some type of rock protection to cover the cables. In either case, these would be “about 10 feet wide either way.”
“Have you spoken with local fishermen, individuals, or groups?” conservation commission member Geoffrey Kontje asked before departing early from the meeting.
“Both, and extensively over a number of years now,” Johnston responded.
Richard Fuka, president of the Rhode Island Fishermen’s Alliance, told The Times that over the course of 16 miles of cable for Deepwater Wind’s Block Island wind project, 16 concrete mattresses had to be sunk. Fuka said they weren’t initially charted, and mobile gear fishermen, fishing squid and fluke primarily, snagged their nets on the mattresses, damaging them. Restitution was an ordeal, he said, because neither Deepwater Wind nor National Grid, its partner in the project, would accept responsibility for the cable. National Grid finally did, he said. Even charted, he described the mattresses as a “pain in the [expletive]” for fishermen. Vineyard Wind hasn’t reached out to him to ask his opinion on mattresses or other cable matters for their Massachusetts project, he said.
Helen Parker, a clinical psychologist from Chilmark, who previously expressed concerns about the Vineyard Wind’s project to the Martha’s Vineyard Commission, told the commission the wind turbines would create harmful infrasound.
“Infrasound, which is sound under the ability of the human ear to hear,” is damaging to humans and marine life, Parker said.
She said she’s worked with people affected by infrasound in Falmouth and Bourne, as well as outside the U.S.
“I have experts who have staked their professional reputation on the fact that these are going to send infrasound to all of the Vineyard and Nantucket,” she said. “It’s going to scramble a lot of people’s brains.”
She said there was extensive research on infrasound, dating back to the 1970s.
“This is the first that I’ve heard that there’s research, and there’s some infrasound effect,” Nathaniel Mayo, manager of development and policy at Vineyard Wind, said.
Parker also said Vineyard Wind and the Bureau of Ocean Energy Management (BOEM) have produced misleading elevation models that show the turbines will be barely visible or not visible in the horizon off the Vineyard. She said they will be.
“These turbines are 795 feet tall — 795 feet is taller than the Prudential Tower,” she said.
The Prudential Tower is 750 feet architecturally, or 920 feet including its antenna, according to the Council on Tall Buildings and Urban Habitat.
Mayo rebutted Parker’s assertion, and said the towers would be 691 feet tall.
“People around the world are watching this because this is a huge installation — the largest in the world,” Parker said.
Johnston said turbine commentary was “not necessarily jurisdictional to this discussion.”
Some discussion also took place about electromagnetic fields.
Johnston told the commission the cable is slated to be buried in the spring of 2021. “We’re hoping for a March start,” she said.