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Greenwich Substation and Line Project

Eversource is starting construction of the new underground transmission lines, modifying the Cos Cob Substation to accommodate the new lines, and removing the warehouse for construction of the new Greenwich Substation.  


As part of always working to serve you better, Eversource is constructing two, new 115-kilovolt (kV) transmission lines and building a new substation to improve reliability in Greenwich, Connecticut.

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 lines will run underground, primarily under town streets, including those in Bruce Park.

The project also includes modifications at the Cos Cob Substation located at 12 Sound Shore Drive.

Greenwich project map

Click to enlarge map

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 Decision issued: November 9, 2017
  • Cos Cob Substation start of modifications: May 12, 2018
  • Start of preparation for warehouse building demolition and pre-construction site preparation for Greenwich Substation: September 12, 2018
  • Start of construction for the new underground transmission lines: April 1, 2019
  • Start of warehouse building demolition for Greenwich Substation: April 1, 2019

Next Steps (estimated timetable, subject to change):

  • Start of construction on remaining project areas: Mid-2019
  • Estimated project completion: Early 2020


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 Decision before construction can begin. These plans include, but are not limited to, further design detail, final site plan, construction sequencing, traffic management plans, work hours and laydown/staging areas. There are multiple D&M Plans for this project.

On February 20, 2018, Eversource submitted the Cos Cob Substation D&M Plan to the CSC. The CSC issued its Decision 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. The CSC issued its Decision on June 21, 2018.

On October 3, 2018, Eversource submitted the Greenwich 115-kV Underground Transmission Lines D&M Plan to the CSC. The CSC issued its Decision on the D&M Plan for the underground transmission lines on January 17, 2019, including the following eight appendices: 

On February 4, 2019, Eversource submitted the Greenwich Substation Construction D&M Plan to the CSC, including the following seven appendices:

On May 3, 2019, Eversource submitted the Indian Harbor Crossing D&M Plan for the 115-kV Double-Circuit Underground Transmission Lines to the CSC for review, including the following seven appendices:



First, please know that Eversource takes every safety precaution while working in local communities, and that all people working on the construction project carry identification.

Please note that the project work will not interrupt electric service to homes or businesses.

Eversource is committed to updating neighbors, businesses and the community about project activities, especially during construction. Public outreach and coordination with the Town of Greenwich is ongoing throughout the project. Eversource representatives will occasionally go door-to-door to communicate with neighbors about the nearby construction project. They may leave an informational doorhanger at a home or business or knock on the door to provide an update on project work.

Construction will take place in phases. Work may occur in several locations along the project route at the same time, and work hours will be location-specific. Please refer to the Traffic Management Plan (TMP) for detailed information on work hours.

The sections below feature construction updates for both substations and the new underground transmission line. As construction progresses, this section will be updated with information for each street affected by construction of the underground lines. Please keep in mind that the construction schedule is approximate and may change. Due to weather or other circumstances, from time to time the crews may need to work longer hours or work on a Sunday.

Modifications to the Cos Cob Substation began in May 2018 and will continue throughout 2019.

Work activities within the existing substation property include vegetation removal; grading, digging and trenching; installation of new equipment and retaining walls; and then restoration of areas disturbed by the work.

Work hours will typically be 7 a.m. to 6 p.m., Monday through Friday, and 9 a.m. to 5 p.m. on Saturdays.

Preliminary survey work began in town streets in February 2019 and will continue through the spring. Work hours will be location-specific and in accordance with the Traffic Management Plan.

Construction of the new 115-kV underground transmission line began the week of April 1, 2019. We anticipate that it will be complete in 2020.

Week of May 5, 2019: 

  • We will continue excavation in Wood Road and Bruce Park Drive in Bruce Park. Traffic detours will be implemented when needed, as shown in Traffic Detour Plans 5 and 6 in the Traffic Management Plan below. Within road closure areas, residents and their guests will be able to access their homes.
  • Excavation work will continue near Cos Cob Substation on Sound Shore Drive. Selective vegetation removal may take place, as needed. 
  • Survey and excavation work will begin on Indian Field Road between Cobb Island Drive and Bruce Park Drive. This work will occur at night, Sunday through Thursday, from 8 p.m. to 5 a.m. Traffic detours will be implemented as shown in Traffic Detour Plan 4.

The warehouse building at 290 Railroad Avenue is being removed for the construction of the new Greenwich Substation.

Preparation for the removal of the existing warehouse and pre-construction site preparation for the substation began in September 2018, and will continue through spring 2019.

Preparation includes the installation of a temporary security fence, removal of the building and related materials, vegetation removal, and grading of the site.

Work hours will typically be 7 a.m. to 6 p.m., Monday through Friday, and 9 a.m. to 5 p.m. on Saturdays.

Construction of the new Greenwich Substation will begin following the CSC's Decision on the D&M Plan. We anticipate that construction will be complete in early 2020.


Working in consultation with town and state officials, including the Connecticut Department of Transportation, Eversource has developed a Traffic Management Plan (TMP) for construction of the Greenwich Substation and Line Project.

The TMP includes hours of construction, area-specific traffic controls and detour plans for each segment of the underground line route.

Some of the files below are large in size and might take some time to load or download. Please note, detour plans are subject to change and may be updated.


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 through 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, please email or call 800-793-2202.