Work Speeds Ahead on Replacing Century-Old Bridges With Tunnel

Seacoast Reliability Project Seeks Permit for Line Work

Thu May 09, 2019 - Northeast Edition #10
U.S. Army Corps of Engineers


The proposed 115 kV transmission Line F107 will run approximately 12.9 mi. from a new 115 kV bay at Madbury Substation to a new 115kV bay at Portsmouth Substation.
The proposed 115 kV transmission Line F107 will run approximately 12.9 mi. from a new 115 kV bay at Madbury Substation to a new 115kV bay at Portsmouth Substation.

Seacoast Reliability Project from Public Service Company of New Hampshire doing business as Eversource Energy Inc. is seeking a permit from the U.S. Army Corps of Engineers, New England District to conduct work in waters of the United States in conjunction with constructing a transmission line from Madbury to Portsmouth, N.H. This work is proposed in wetlands and waters between the Madbury Substation to the Portsmouth Substation, in New Hampshire.

The proposed work involves both direct permanent and temporary discharges of dredged or fill material into various wetlands and waters of the United States along the proposed route to provide a parallel path to enhance the existing 115kV loop between the Deerfield and Scobie Pond Substations in order to address reliability concerns in the New Hampshire Seacoast Region, which have been previously identified by the Independent System Operator-New England (ISO-NE). The proposed line will be compromised of overhead transmission structures and conductor, underground cable and submarine cables.

The proposed 115 kV transmission Line F107 will run approximately 12.9 mi. from a new 115 kV bay at Madbury Substation to a new 115kV bay at Portsmouth Substation. The transmission line will be located primarily within an existing electric utility corridor that is currently occupied by a 34.5 kV overhead distribution supported by direct embedded wood pole structures.

There will be two terrestrial sections of the new 115kV line that will be constructed underground with three solid dielectric insulated cables installed in individual PE conduits. Additionally, there will be one new 115kV line that will be constructed completely underwater with three specialized solid dielectric insulated submarine cables directly buried across Little Bay.

Impacts to wetlands and waters of the United States include approximately .02 acre of permanent impact to non-tidal wetlands and 0.2 acre of permanent impacts to tidal wetlands. Permanent impacts are associated with the installation of new transmission line structures in terrestrial areas and the need for concrete mattresses for cable protection in estuarine areas. Temporary impacts include approximately 7 acres to non-tidal wetlands, 0.01 acre to river/stream, and 6 acres to tidal wetlands. Temporary impacts are associated with timber matting along access roads and for work pads and for impacts associated with installation of the marine cables using jetplow and hand-jetting technology.

The proposed project will have an adverse effect on approximately 7 acres of Essential Fish Habitat (EFH). This habitat consists of fine sand, silt and soft mud in the intertidal zone and in deeper areas the substrate is made up of fine to medium sands, silts, clay and shell fragments. Loss of this habitat may adversely affect species that use these waters and substrate. The Corps has made a preliminary determination that site-specific impacts may be substantial. Accordingly, the Corps submitted an EFH assessment to the National Marine Fisheries Service for EFH consultation.

The application for the federal permit was filed with the Corps in compliance with Section 10 of the Rivers and Harbors Act, which provides for federal regulation of any work in, or affecting navigable waters of the U.S.; and Section 404 of the Clean Water Act, which regulates the discharge or fill of material in U.S. waters, including wetlands.

For more information, visit nae.usace.army.mil/Missions/Regulatory/PublicNotices.aspx.