Mayflower Wind offshore electric cables to run through Portsmouth 

PORTSMOUTH – Holding one of the seven leases for proposed wind farms in 1,400 square miles of federal waters near the coast of Nantucket and Martha’s Vineyard, Mayflower Wind officials say its lease, with 149 massive turbines running at full capacity, could generate enough electricity to power a million homes in the state of Massachusetts.

To get the power onshore, however, they want to go directly through Portsmouth.

Rhode Island’s Energy Facility Siting Board notified the Portsmouth Town Council on June 16 that Mayflower Wind had officially applied to connect its offshore wind farm with a planned regional transmission facility in Somerset via two cables running up the Sakonnet River, underground for two miles across Island Park and into the Mount Hope Bay.

Those cables would transmit half of the farm’s power capacity, or 1,200 megawatts, to a proposed transmission station located at Brayton Point in Somerset, Massachusetts, home of New England’s last coal-fired power plant until it shut down in 2017. The transmission station would then supply the Southcoast region of Massachusetts.

Mayflower Wind is also going through an application process to run the other 1,200 MW of capacity to Cape Cod through the town of Falmouth, where it has run into some local apprehension. The company has additionally applied for a Noticed Variance in Portsmouth, which would leave the door open for a second pair of cables to run to Brayton Point in the event that it makes the most sense for the company to route all 2,400 MW to Somerset.

Why does Mayflower Wind want to run the cables through Portsmouth?

In short, the route across Island Park in Portsmouth is the best available route to Somerset because the cables need to run up the Sakonnet River, but the channel leading from the Tiverton basin into Mount Hope Bay poses a number of difficulties that are avoided by going underground across the peninsula.

The cables need to run up the Sakonnet River because Mayflower met with the US Navy while discussing proposed routes, and the Navy, which has a large presence on the western shore of Aquidneck Island, would not allow the cables to run through restricted areas, regulated navigation areas and naval anchorage in and around the East Passage of Narragansett Bay.

What does the Portsmouth component of the transmission cables entail?

Lawrence Mott, Mayflower’s transmission development manager, explained the details of the proposal in a “virtual open house” held on May 4, which is still available on YouTube. Talking to The Newport Daily News, Mott stressed that public engagement was important to Mayflower and the proposal was still at an early stage. Mayflower’s current timeline would see its proposed construction starting in Portsmouth no earlier than December of 2024.

Mott explained that rather than dealing with the currents, boat traffic, underwater debris and demolished bridges under the Sakonnet Bridge, Mayflower intends to use “horizontal directional drilling” (HDD) to run the cables from the Sakonnet riverbed west of Gould Island to the shoulder of Park Avenue, where they would then run north towards Montaup Country Club in a trench along the east side of Boyd’s Lane.

The HDD would entail steering a 24-inch diameter drill bit from the north side of Park Avenue in an inverted arc to apex 20-40 feet underground and then surface underwater in the river. Mott explained that the HDD could drill deep underneath the street, seawall and intertidal zone without impacting the environment or daily recreation in Island Park. A waiting barge would then feed a polyethylene conduit back through the drilled hole, which would be pulled back to land and routed north in a trench alongside Boyd’s Lane.

There are several proposed routes for the cables to reenter the water in Mount Hope Bay: one slightly east of the Mount Hope Bridge, one through the existing utility easement near Roger Williams Baypoint residence hall, and one through the Montaup Country Club parking lot. The cables would then route parallel to the coast of Tiverton around Spar Island before turning north and crossing the bay to Brayton Point.

Mayflower Wind and Mott specifically will be engaging regularly with the public leading up to Mayflower’s public hearing with the Rhode Island Energy Facility Siting Board on August 18, including a second virtual open house scheduled for August 16. As with the previous open house, Mayflower intends to advertise online and in the local newspaper and canvass houses door to door.

The Portsmouth Town Council also indicated in its most recent meeting that they would be inviting Mayflower to give a public presentation on the proposed transmission cables at their next meeting on August 9.

Mayflower spokesperson Joyce McMahon confirmed that Lawrence Mott would be in attendance to present the proposal and take questions from councilmembers and Portsmouth residents.