Why Are We Doing This Project?

As part of our ongoing commitment to deliver reliable energy and superior service to our customers, we are proposing replacement of two existing 115-kilovolt (kV) high pressure fluid-filled (HPFF) underground electric transmission lines with new 115-kV solid cross-linked polyethylene (XLPE) electric transmission cables.

The two underground transmission cables, installed in 1955, extend for about 1.95 miles from our Mystic substation in Boston/Everett, across the Mystic River, to our substation in Somerville. Replacing the existing HPFF lines with XLPE cable will modernize the existing transmission system and increase reliability.

These improvements will help Massachusetts achieve its net-zero carbon emissions goal by 2050. The proposed project is part of a larger program we are conducting throughout our service territory in Connecticut and Massachusetts related to underground cable modernization. This program is designed to modernize and increase the capacity of the existing underground transmission cable systems by replacing existing HPFF cables with XLPE cables.

Where Is This Work Being Done?

The proposed underground transmission lines targeted for upgrades run from Mystic substation adjacent to Alford Street in Boston to the Somerville substation on Prospect Street in Somerville.

We are reviewing possible routes to install the new lines, including along the existing route. We welcome and appreciate the opportunity to integrate feedback into the routing.

Once the new lines are installed, the existing HPFF transmission lines will be retired.

*Click map to enlarge

When Is The Work Being Done?

• File Siting Petition with the EFSB: Q4 2025
• All permits received: Q2 2027
• Start of construction: Q1 2028
• Projected construction completion: Q4 2030
• Commissioning and project restoration: Q1 2031

*Subject to change, pending necessary approvals

Siting Review

The project filling type is yet to be determined. Environmental permits will also be required from local, state and federal agencies.

Community Outreach

We are committed to engaging city officials, residents, and businesses and community groups as we conduct these reliability upgrades.

We are committed to providing meaningful opportunities to participate in the project development process, and to incorporate local feedback into the project’s development as feasible.

Project information is available in Spanish, Portuguese and other languages upon request.