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United States

Long Island Replacement Cable Project: Norwalk, Connecticut to Northport, New York

TRC managed marine surveys, environmental impact evaluations, regulatory permitting, and environmental monitoring for three 11-mile, 300 MW Alternating Current (AC) submarine cables that replaced a series of electric transmission cables connecting Connecticut and Long Island.

To evaluate potential submarine cable routes, TRC conducted extensive geophysical and geotechnical surveys of seabed conditions within Long Island Sound. As part of this effort, TRC oversaw a multi-disciplinary technical team that specifically conducted remote sensing surveys of marine seabed conditions, geotechnical borings, and sediment thermal profiles to assist in developing appropriate installation methodologies.

TRC also led comprehensive environmental impact evaluations associated with selected cable routes and landfall locations, which included impact assessments of shellfish and finfish resources, water quality, prevailing tides and currents, and navigational and marine hazards.

TRC prepared federal, state, and local regulatory permit applications and managed the overall regulatory permitting process including the Connecticut Siting Council and New York State Department of Public Service reviews for the project.

During construction activities, TRC acted as the lead Environmental monitor for the project both in Connecticut and New York State. TRC developed the monitoring plan and managed the implementation of total suspended solids monitoring during cable removal and embedment, as well as post-construction environmental monitoring efforts in New York and Connecticut waters.

TRC has also completed initial post-construction monitoring, which included multiple benthic surveys in Sheffield Harbor and a two-year concrete mattress biological monitoring program adjacent to Sheffield Island. TRC continues to provide post-construction environmental monitoring, currently consisting of biennial hydrographic surveys of the three LIRC cables.


  • Geophysical & Geotechnical Survey Oversight
  • Environmental Impact Investigations
  • Benthic Investigations
  • Sediment Transport & Dispersion Analyses
  • Navigational Impact Investigations
  • Permitting
  • Environmental Monitoring
  • Expert Testimony

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