Final Decision
The Siting Board issued its Final Decision in this proceeding on February 27th, 2026 and can be viewed by clicking on the available link.
The full Decision was also issued in Spanish, Portuguese, Haitian Creole, Simplified Chinese, and Arabic.
February 26 Board Meeting
The Energy Facilities Siting Board (“Siting Board”) will conduct a hybrid Siting Board meeting on Thursday, February 26, 2026, starting at 9:00 A.M.
Trimount ESS LLC, EFSB 25-05/D.P.U. 24-152 - At 9:00 A.M., the Siting Board will meet, deliberate, and vote on a Tentative Decision in the Trimount ESS LLC proceeding. Trimount ESS LLC is seeking (1) approval to construct, operate, and maintain two underground transmission lines, one at 115 kilovolt (“kV”) and one at 345 kV; and (2) individual and comprehensive zoning exemptions from the City of Everett Zoning Ordinance in connection with the Company’s proposed construction of an approximately 700 megawatt (“MW”)/2,800 megawatt-hour (“MWh”) battery energy storage system (“BESS”) and associated infrastructure including two substations, in Everett. The Tentative Decision and more information on this matter may be found at the available link.
2024 Climate Act Regulations, EFSB 25-10 - Immediately after the vote on EFSB 25‑05/D.P.U. 24-152, the Siting Board will consider regulations implementing the siting and permitting reforms from An Act promoting a clean energy grid, advancing equity and protecting ratepayers,” St. 2024, c. 239 (the “2024 Climate Act”). The Siting Board will hear staff presentations on comments received on the proposed regulations and guidance listed below. The Siting Board will not vote on the proposed regulations at this meeting. The Siting Board will hear public comment as time allows. Further information on the Siting Board’s 2024 Climate Act regulations are available by clicking the following link.
Remote attendees: join by using the available link from a computer, tablet, or smart device. For audio-only participation attendees can dial in at (646) 558‑8656 (not a toll-free number) and then enter the Webinar ID: 873-7169-9465.
In-person meeting location: One South Station, Boston, MA 02110, 3rd floor, Large Hearing Room. Building security requires a government-issued photo ID. Nearby transit station: South Station (Red Line).
The Open Law Meeting Agenda is now available through the following link. The full Notice can now be accessed at the available link.
Please find below the Tentative Decision for EFSB 25-05/D.P.U. 24-152. We anticipate that a Board Meeting will be held in the morning at 9:00 AM on February 26, 2026. Written comments are due on the Tentative Decision no later than February 23, 2026.
Tentative Decision: English | Spanish | Portuguese | Haitian Creole | Simplified Chinese | Arabic
Proposed Staff Amendments: English | Spanish | Portuguese | Haitian Creole | Simplified Chinese | Arabic
The recording for this hearing will be available on the Siting Dvision's YouTube Channel.
Evidentiary Hearings
The Siting Board held an evidentiary hearing in the above-referenced matter on August 12th, 13th, 25th, and 27th, 2025.
Note: Hearings scheduled for August 27th, 2025 are cancelled.
Video recordings of the hearing can now be accessed at the DPU YouTube channel.
Extended Public Comment Period
As described in the Notice of Extended Public Comment Period, the Siting Board is extending the deadline to file written comments and the deadline to file for intervention/limited participant status two weeks from the current deadline of April 25, 2025, to Friday, May 9, 2025.
Link to the full notice can be accessed here.
Translations are available in Spanish, Portuguese, Haitian Creole, Arabic, and Standard Chinese.
Public Comment Hearing
The Siting Board conducted a hybrid public comment hearing with both in-person and remote participation options on Tuesday, April 8, 2025, at 6:30 P.M.
Location: The Connolly Center, 90 Chelsea Street, Everett, MA 02149
At the public comment hearing, the Company presented an overview of the Project. Public officials and members of the public had an opportunity to ask questions and provide comments about the proposed Project. The public comment hearing was transcribed by a court reporter. A recording of the public comment hearing is now available on the Siting Board’s YouTube channel.
Link to the full notice can be accessed here. Translated copies of this notice are available in Spanish, Haitian Creole, Arabic, Portuguese, and Standard Chinese.
Project Information
The Company proposes to construct an approximately 700 MW/2,800 MWh BESS, located on the North and South Parcels of the Project Site, separated by Beacham Street in Everett. The BESS would charge with power from the electric grid during periods when there is excess energy and deliver power back onto the electric grid during times when there is a need for electricity.
The Project would use lithium-ion batteries housed in approximately 816 above-ground enclosures. The Project’s BESS units will be placed in a double-stack orientation (see Figure 3 below). Half of the BESS units and inverters would be on an industrial steel platform, and the other half of the BESS units would be below the platform. Each BESS enclosure would be approximately 19.7 feet long, 7.9 feet wide, and 9.5 feet tall. Each BESS unit would be on pier foundations and would be set on concrete pads.
Each BESS unit’s thermal safety would be managed by an integrated cooling and heating system. The system contains sensors that support embedded monitoring and controls as well as electrical interface equipment including industry standard breakers for alternating current (“AC”) protection. The Project would also include power conversion systems, medium-voltage transformers on concrete slabs and pier foundations, medium voltage cables, and other electric infrastructure (collectively, the “Collection System”).
The Project would occupy approximately16.5 acres of the 20.75-acre Project Site. The current use of the Project Site is a former ExxonMobil oil terminal, now undergoing environmental cleanup.
The Northern Parcel is about 9.7 acres in size, and the BESS units along with all other project components/features would occupy approximately 8.2 acres of previously developed land. The Southern Parcel is about 11.1 acres in size, and it would include BESS units along with all other project components/features and would occupy approximately 8.25 acres of previously developed land.
The Project would include two new electric substations (“Project Substations”), one on the Northern Parcel (345 kV) and one on the Southern Parcel (115 and 345 kV). Each Project Substation would take the power output from the BESS units and step it up to a transmission voltage, which would allow the power from the Project to interconnect with the existing Eversource Mystic Substation.
The Project Substations would also take the power from the Mystic Substation and step it down to allow the BESS to store the power. The project would utilize 345 kV underground electric lines to connect battery enclosures and power control systems to the project substations, including crossings beneath Beacham Street.
The Project would include one newly constructed 115 kV underground transmission line and one newly constructed 345 kV underground transmission line. The newly constructed lines would connect the BESS to the Mystic Substation. The Northern Parcel Project Substation would be connected to the Southern Parcel Project Substation via a 345 kV high voltage line that would run under Beacham Street into the Southern Parcel. Both the 345 kV and the 115 kV transmission lines would exit the Southern Parcel Project Substation and run directly to the Mystic Substation. When they exit the Southern Parcel, the two transmission lines would travel together for roughly 1,600 feet.
Then, the 345 kV line separates and interconnects with the 345 kV interconnection point at the Mystic Substation. From the point of separation of the two lines, the 115 kV line would travel roughly 1,200 feet farther to reach its interconnection point at the 115 kV interconnection point at the Mystic Substation. After exiting the Project Site, the proposed transmission line route for both lines first utilizes a private easement, then enters Robin Street, then enters Dexter Street, and finally (for the 115 kV line only) Alford Street.
EFSB 25-05 in the DPU Fileroom.
The figures below show: (1) the location of the Project Site within the City of Everett with connection to the existing Mystic Substation; and (2) the conceptual battery energy storage system proposed double-stack layout (subsection).
Project Filing with EFSB
- Company's Petition
All documents related filed in relation to a proceeding are posted to the DPU Fileroom. The Fileroom page for a proceeding represents the official record for that proceeding. The public can access the Fileroom page for this proceeding at the following link:
Public Review of the Company's Petition
A detailed description of the Project, links to the Company’s petitions, attachments, and analysis,
and periodic updates are available via the Siting Board’s webpage for the Project
The Company also maintains a webpage for the Project. The Company’s webpage provides Project information in
English, Spanish, Haitian Creole, and Brazilian Portuguese.
Hard copies of the Company’s petitions, including all attachments, are available for public inspection at the following locations:
Boston
Energy Facilities Siting Board
One South Station, 3rd floor, Boston, MA 02110
Boston City Clerk’s Office
1 City Hall Sq Ste 601,
Boston, MA 02201
Boston Public Library
179 Main St,
Charlestown, MA 02129
Everett
Everett Clerk’s Office
484 Broadway, Room 10
Everett, MA 02149
Parlin Memorial Library
410 Broadway
Everett, MA 02149
Decision on the Project Proposal
The public comment hearing marks the beginning of an official, state-level decision-making process focused on whether the Project should be approved. The Siting Board will make the decision based on the following laws:
- Under G.L. c. 164, §72, the Siting Board will review the Company’s proposed Project to determine whether the Project is necessary, serves the public convenience, and is consistent with the public interest.
- Under G.L. c. 40A, § 3, the Siting Board will review the Company’s proposed Project to determine whether the zoning exemptions should be granted, and if the proposed use of the Project Site is reasonably necessary for the convenience or welfare of the public.
Accommodation Requests
Reasonable accommodations for people with disabilities (e.g., Braille, large print, electronic files, audio format) are available upon request. To submit a request for an accommodation, please email Melixza Esenyie - Non-Discrimination Coordinator and Director of Diversity, Equity, and Inclusion, Massachusetts Executive Office of Energy and Environmental Affairs at, eeadiversity@mass.gov, 617-626-1282. In your communication, please include a description of the request with as much detail as possible and provide a way we can contact you if we need more information. Please allow at least one week (7 days) advance notice. Last minute requests will be accepted, but we may be unable to fulfill them.
Spanish, Haitian Creole, Brazilian Portuguese, Arabic, and Chinese (Mandarin) interpretation will be provided for the public comment hearing. Additional language interpretation services are available upon request. Include in your request the language required and a way to contact you if we need more information. It may not be possible to accommodate last-minute requests. Contact the Presiding Officer for more information (contact information below).
Non-Discrimination Notice
The Energy Facilities Siting Board (“EFSB”) does not discriminate on the basis of race, color, national origin, disability, age, sex, income, ethnicity, class, disability, religious creed or belief, gender identity, sexual orientation, genetic information, English language proficiency or ancestry in administration of its programs or activities. See the EFSB’s Non-Discrimination Notice
If you have any questions about this notice or any of the Siting Board’s non-discrimination programs, policies, or procedures, you may contact: Melixza Esenyie - Non-Discrimination Coordinator and Director of Diversity, Equity, and Inclusion, Massachusetts Executive Office of Energy and Environmental Affairs, Human Resources, 9th Floor, 100 Cambridge Street, Boston, MA 02114, eeadiversity@mass.gov, 617-626-1282.
If you believe that you have been discriminated against with respect to a Siting Board program or activity, you may contact Melixza Esenyie (identified above) to learn how and where to file a complaint of discrimination.
Contact
For further information about the proceeding, please contact the Presiding Officer at the address or telephone number below:
Connor Tarr, Presiding Officer
Energy Facilities Siting Board
One South Station
Boston, MA 02110
617-305-3625
Connor.Tarr@mass.gov
| Last updated: | February 13, 2026 |
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