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Greenwich Substation and Line Project

Eversource's application to build new transmission lines and a substation in Greenwich, Conn., was approved in November 2017.


At Eversource, we're always working to serve you better. We are preparing to construct new 115-kilovolt (kV) underground transmission lines and build a new substation to enhance our ability to reliably serve customers in Greenwich.

The new lines will extend 2.3 miles from Eversource’s existing Cos Cob Substation on Sound Shore Drive to the new Greenwich Substation at 290 Railroad Avenue. The new lines will run underground, primarily within town streets, including the streets in Bruce Park.

In addition to the new substation and transmission lines, modifications will be made at the Cos Cob Substation located at 12 Sound Shore Drive.

Project Facts:

  • Underground route length: 2.3 miles
  • Location: Greenwich, Connecticut
  • Line voltage: 115,000-volt (115-kV) transmission line
  • Substation: One new transmission-level substation and modifications to the existing Cos Cob Substation
  • Siting review by: The Connecticut Siting Council (CSC)
  • Application filing to the CSC: June 26, 2015
  • CSC approval issued: November 9, 2017
  • Cos Cob Substation Development & Management (D&M) Plan approval: April 12, 2018
  • Cos Cob Substation start of construction: May 12, 2018
  • Greenwich Substation Warehouse Building Demolition and Pre-Construction Site Preparation Development & Management (D&M) Plan approval for Greenwich Substation: June 21, 2018
  • Start of warehouse building demolition and pre-construction site preparation for Greenwich Substation: September 12, 2018

    Next Steps (estimated timetable, subject to change):

    • Development & Management (D&M) Plans (construction plans) to CSC for approval: First - Third Quarters 2018
    • CSC Decision on remaining D&M Plans: Third Quarter 2018
    • Start of construction on remaining areas: Third - Fourth Quarters 2018 


Following receipt of the CSC’s application approval, Eversource is required to submit construction plans, called Development & Management Plans (D&M Plans), to the CSC for its approval before construction can begin. The D&M Plans include, but are not limited to, further design detail, final site plan, construction sequencing, traffic management plans, work hours and laydown/staging areas.

On February 20, 2018, Eversource submitted the Cos Cob D&M Plan to the CSC, and the Plan was approved by the CSC on April 12, 2018.

On May 18, 2018, Eversource submitted the Greenwich Substation Warehouse Building Demolition and Pre-Construction Site Preparation D&M Plan to the CSC, and the Plan was approved by the CSC on June 21, 2018.

Eversource intends to submit the remaining D&M Plans, for the new transmission lines and construction of the new Greenwich Substation, to the CSC in the coming months.  The D&M Plans will be posted to this web page as they become available.  


Eversource will begin construction of the approved portion of the project after receipt of the CSC's approval of each D&M Plan. Work will be done in sections, rather than continuously in any one area.

Construction in the Cos Cob Substation began on May 12, 2018, and will continue through 2019. Construction within the existing substation property will include vegetation removal; grading, digging and trenching; installation of new equipment and retaining walls; and then restoration of areas disturbed by the work.

The hours for construction in the Cos Cob Substation will typically be 7 a.m. to 6 p.m., Monday through Friday, and 9 a.m. to 5 p.m. on Saturdays. Due to weather or other circumstances, from time to time the crews may need to work longer hours or work on a Sunday.


Beginning with municipal briefings and other community outreach efforts, Eversource engages the community throughout the lifecycle of a project to provide information, answer questions and listen to concerns.

As the project proceeds to construction, Eversource is committed to updating neighbors, businesses, and the Greenwich community about construction activities in the area. 


For more information about the Greenwich Substation and Line Project, send an email to or call 800-793-2202.