Offshore to onshore connection
Wind Turbines – Wind turbines convert kinetic energy from the wind into electric power.
Inter-array Cables – Electrical cables connect wind turbines to each other and transport power to the offshore substation at 69 kilovolts (kV).
Offshore Substations – The offshore substations enables the wind farm to operate more efficiently by stepping up voltage from 66 kV to 200-345 kV.
Export Cables – Electric power is transmitted from the offshore substations by electrical cables which will come ashore in Falmouth.
Landfall – The export cables connect onshore via an underground conduit tunneled deep beneath the beach.
Underground Cables – From the beach area, electric cables will be buried beneath town roads and transmit power to the onshore substation.
Onshore Substation – The onshore substation transforms the power to grid voltage, stepping up to 345 kV.
Overhead Lines – An overhead 345 kV transmission line transports the power to an interconnection switching station.
POI – The point of interconnection, or the point where SouthCoast Wind’s facilities interconnect with the Transmission Owner’s facilities.
Interconnection Switching Station – The interconnection switching station collects power from the overhead lines and feeds into the transmission system.
Transmission System – An interconnected network of 345 and 115 kV transmission lines deliver electricity to end customers.
A strong commitment to safety
While we will examine the safety of all aspects of the project, one topic of community interest is electro-magnetic fields (EMF). We hired expert consultants to study the potential EMF effects of the cable. They found that there are no safety risks and SouthCoast’s electric cables will operate well below established health guidelines. For more information and to view the reports, please see our Health and Safety page.
Getting from there to here
The SouthCoast Wind project will be located over 30 miles south of Martha’s Vineyard and 20 miles south of Nantucket.
Submarine export cables buried beneath the seafloor will run north through Muskeget Channel and then west towards Vineyard Sound, before making landfall in Falmouth. From there, electric cables buried under roadways will connect power to an onshore substation in Falmouth, and underground transmission lines will deliver power to the Falmouth point of interconnection with the regional electric grid.
SouthCoast Wind has identified three potential locations for the subsea export cables to make landfall in Falmouth which are based on several criteria including wetlands, abutters, traffic, archeological significance, etc. The preferred landing is Worcester Avenue, the alternate is Central Park and the third option is Kite Park. The analysis of landing sites was presented to the town and can be found on the Falmouth, MA website.
The cables will be installed under the beach and coastal ecosystem. Each proposed HDD trajectory will be about one mile in length, at a depth of up to 90 feet below the seabed. Once ashore, the cables will continue underground, in nearly all cases under roadways up to eight feet or deeper, to a much further inland onshore substation at a location that is being determined.
The Falmouth Heights beach locations were selected after initial modeling confirmed the Upper Cape as an optimal point of interconnection into the regional electric grid. Locations along Surf Drive Beach were intensively studied but proved infeasible, largely due to technical issues created by existing utility lines.
Studies are being conducted to gather data and assess the suitability of these sites for a complete and reasoned analysis of the preferred and alternative routes.
A final decision on site location will be made after a full routing analysis has been completed. That decision will then be reviewed and require approval by state and local regulatory agencies.
Horizontal Directional Drilling
How HDD will work
Following the guidance of the Massachusetts Ocean Management Plan, which protects critical marine habitat and important water-dependent uses and sets standards for ocean-based projects, SouthCoast Wind will employ Horizontal Directional Drilling (HDD) to avoid impacts to sensitive environmental resources, including beaches and nearshore eelgrass beds.
The process begins with the creating of a bore hole to support the cable. It will be located well below the surface and will come up well distant of the beach. Each proposed HDD trajectory will be about one mile in length, at a depth of up to 90 feet below the seabed.
After the bore hole is created, the cable will be pulled through and buried under the beach. Using a duct bank and vault system, the cables will then be buried under local roads and connect to a new substation much further inland. Manhole covers all you will be able to see, just like those found along Surf Drive Beach for the existing fiber optic and electric cables to Martha’s Vineyard.
Underground route to substation
The onshore cable route will primarily be installed within existing paved roadways or roadside shoulders. The anticipated method of underground cable installation along the route is open trench installation. Typical excavation depth will be approximately eight feet deep but could be deeper depending on survey results.
The total length of the buried cable from the landfall to the substation is two to eight miles, depending on the location. The preferred location for the substation is at the Lawrence Lynch aggregate and asphalt facility on Stephens Lane. The alternative site is at Cape Cod Aggregates facility located off Thomas B. Landers Road.
The cables will operate at a voltage between 200-345 kilovolts. While most high-voltage transmission lines remain overhead, a growing number of systems include underground 345 kilovolt cables through densely populated areas, including a recent Eversource project from Woburn to Wakefield.
The maximum footprint of the onshore substation site will be up to 26 acres. Major components at the onshore substation include air-insulated circuit breakers, switchgear, and 345 kilovolt transformers. As the substation equipment and layout is refined, SouthCoast Wind will refine noise mitigation strategies such as low-noise transformers, enclosing of certain substation components, and sound barriers.
Connecting at Falmouth Tap
Eversource will be responsible for constructing and operating a new two- mile overhead line to the point of interconnection at Falmouth Tap, as well as the Falmouth Tap grid connection.
Falmouth Tap currently consists of an existing substation owned by Eversource, which will be upgraded in the future to accommodate SouthCoast Wind.
The Falmouth Tap grid connection provides access to the existing 345 kilovolt overhead transmission lines that transmit across the Cape Cod Canal to Carver and Plymouth. An interconnected network of transmission and distribution lines ultimately deliver electricity to end customers of the New England regional system.
Contact our community liaison
Kelsey Perry is the project’s Community Liaison Coordinator. In this role, Kelsey serves as the link between the Falmouth community and SouthCoast Wind. She listens to residents and shares project updates and information to strengthen communication and collaboration.
This page will be updated frequently so we encourage you to visit often and/or sign up for our email updates.