UI Announces Derby-Ansonia Transmission Line Rebuild

The project replaces four miles of aging infrastructure

ORANGE, CT – March 14, 2022 – Today the United Illuminating Company (UI) – a subsidiary of AVANGRID, Inc. (NYSE: AGR) – announced its proposal for a major transmission project in the Naugatuck River Valley. By replacing aging infrastructure that is close to 100 years old, this major rebuild will enhance the integrity of the transmission system while further strengthening the reliability and integrity of the electric grid. The project also meets the growing energy demands of the Derby, Ansonia and Shelton communities.

“UI has a strong record of reliable service to customers and is among one the most reliable energy companies in the country. As part of our continued commitment to providing safe and reliable service, we are rebuilding the electric transmission system in the Derby, Ansonia and Shelton communities through this project,” said Frank Reynolds, President & CEO of UI. “This project is the latest example of the ongoing work across our service territory that will better equip us to meet the energy demands of our customers and further strengthen the resiliency of our electric grid.”

The genesis of this project spurred from extensive research done in 2012 at UI to assess existing 115-kilovolt (kV) transmission lines. As a result of these comprehensive engineering studies, it was determined that the existing lines would need to be replaced to maintain safe and reliable power to customers.

“This project is ten years in the making, and a major infrastructure improvement for our customers in the Naugatuck Valley and the surrounding region,” said Project Manager Kevin McMahon. “It will greatly strengthen our resiliency and enable us to better serve these communities.”

Within the plan, UI proposes to replace its three existing 115 kV lines that collectively run a distance of approximately 8.15 circuit miles (4.1 miles) from Derby Junction in the Town of Shelton, connecting to the Ansonia Substation in the Town of Ansonia via Indian Well Substation in the Town of Derby.

“We are meeting the community’s growing energy demands while working closely with town officials, local tree wardens and with residents and customers to ensure that all improvements are performed safely and with minimal disruption to the environment and the community,” added Reynolds.

Once the project is approved, UI will begin the transmission line construction process. There are seven main stages of the transmission line construction process:

  1. Survey: Prior to beginning construction activities in any given area, survey crews walk every mile of the route to mark construction locations and right-of-way (ROW) limits in accordance with the approved Environmental Protection and Construction Plan (EM&CP). The survey crews will use different colored flags and stakes to identify clearing limits, danger trees, access roads, structure locations and workspaces, and sensitive natural resources.
  2. Clearing: Before construction can begin, vegetation from the ROW must be removed to assist crews in creating a safe, level work surface, and to remove vegetation and trees capable of growing into the transmission lines and "danger trees" that could fall into the lines. After tree removal, the work area will look different, however, native shrubbery and ground cover will typically grow back.
  3. Road Work: Existing roads and parking lots will be used where practical. Where necessary, new access roads will be constructed, preferably within the ROW. Timber mats will be used to protect lawns, agricultural fields and other sensitive areas such as wetlands. After construction is complete and the area is completely rehabilitated, the company will restore roads and entrances as required. Strict run-off controls will be in place and managed throughout the project.
  4. Foundation Work: Structure types and heights are based on the unique engineering requirements for each project location. The structures that will be used for the Project are steel single circuit monopole structures and will either be direct embed or erected on concrete foundations. For structures with foundations, concrete will be delivered by truck.
  5. Structure Placement: Once foundations are in place, construction crews will erect the structures within the ROW. Steel poles will be assembled using a truck-mounted crane then lifted onto the foundations. Embedded structures will be placed into excavations which will be backfilled.
  6. Wire Work: Insulators and attachment hardware will be installed and stringing sheaves (rollers or blocks) attached to the insulators. The conductors will be strung by attaching the conductor to a steel line and pulled through each structure’s stringing sheaves under tension to keep the conductors well off the ground. Conductor pulling sites located along the ROW will provide space for tractors, trailers with spools of conductor, and tensioning equipment.
  7. Restoration: After all construction activities have been completed, ground cover and vegetation are encouraged to grow back. In some areas vegetative buffers or other landscaping may be installed. Good construction practices will be used to stabilize disturbed soils to promote re-vegetation and progress will be monitored. If any damage occurs to roads, they will be restored to their original state.

For more information on the Derby-Ansonia Transmission Line Rebuild, visit this link.


About UI: The United Illuminating Company (UI) is a subsidiary of AVANGRID, Inc. Established in 1899, UI operates approximately 3,600 miles of electric distribution lines and 138 miles of transmission lines. It serves approximately 341,000 customers in the greater New Haven and Bridgeport areas of Connecticut. UI received the Edison Electric Institute’s Emergency Recovery Award in 2019 and 2021. For more information, visit uinet.com.  

About AVANGRID: AVANGRID, Inc. (NYSE: AGR) aspires to be the leading sustainable energy company in the United States. Headquartered in Orange, CT with approximately $39 billion in assets and operations in 24 U.S. states, AVANGRID has two primary lines of business: Avangrid Networks and Avangrid Renewables. Avangrid Networks owns eight electric and natural gas utilities, serving more than 3.3 million customers in New York and New England. Avangrid Renewables owns and operates a portfolio of renewable energy generation facilities across the United States. AVANGRID employs approximately 7,000 people and has been recognized by Forbes and Just Capital as one of the 2021 JUST 100 companies - a list of America's best corporate citizens - and was ranked number one within the utility sector for its commitment to the environment and the communities it serves. The company supports the U.N.’s Sustainable Development Goals and was named among the World’s Most Ethical Companies in 2021 for the third consecutive year by the Ethisphere Institute. For more information, visit avangrid.com.   

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