Eversource goes underground: Utility breaks ground on first-of-its-kind substation, part of $1.5B transmission project

Eversource and project partners celebrate the groundbreaking for the Greater Cambridge Energy Program (Photo: Business Wire)

Eversource has broken ground on the Greater Cambridge Energy Program (GCEP), a $1.5 billion transmission initiative meant to address increased electric demand in the region by adding new transmission lines and constructing an underground substation, a first for the utility. It is slated to be the largest underground electrical substation in the United States once it is completed.

The GCEP project will enable the interconnection of more new clean energy resources, necessary to support a strained grid amidst a nationwide increase in electrification across sectors. as customers adopt technologies like EVs and heat pumps.

A rendering of Eversource’s planned underground substation, part of its Greater Cambridge Energy Program (GCEP).

Designed to place a “significant amount” of needed infrastructure underground, the GCEP’s planned substation will be a whopping 35,000 square feet, located 105 feet underground. The first underground substation in the U.S. was built by Anaheim Public Utilities in 2006.

As energy demand continues to increase in Cambridge and surrounding areas, Eversource argues the output from GCEP’s underground substation will enable “far-reaching” electrification of heating systems in the city, providing capacity to address 100% of residential heating electrification as well as the ability to displace 50% of the commercial sector’s gas demand through electrification.

Eversource’s $1.5 billion plan for an underground substation and associated transmission lines in Cambridge, Mass. (Courtesy: Eversource/EFSB)

As part of GCEP, Eversource will also construct eight new 115 kV underground transmission lines spanning 8.3 miles through portions of Cambridge, Somerville, and Boston. Additional work includes upgrades to five substations, or “clean energy hubs,” in Cambridge, Somerville, and Allston/Brighton, and the construction of 48 new distribution lines.

Eversource anticipates to begin putting GCEP into service in 2029 with the energization of the substation and the first transmission line. As construction proceeds, the energy company expects that the remaining transmission lines will be put into service through 2031. Throughout the project, approximately 500 full-time jobs will be supported.

“The GCEP is a true example of public and private partnership created to solve a critical community challenge. BXP is incredibly proud and fortunate to partner with Eversource, the CRA, and the City of Cambridge to provide a below-grade space for the substation which will power the future of Cambridge,” said Bryan Koop, Executive Vice President for BXP’s Boston region.

Eversource originally received tentative approval from a Massachusetts siting board to build the underground substation last June.

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