During the period 7 to 9 September 2010, a magnetic field intensity study was conducted by Ocean Surveys, Inc. (OSI) in and around Sheffield Harbor, Norwalk, CT, and in a portion of Long Island Sound. This task was part of a monitoring program designed to assess the potential environmental effects of the Long Island Power Authority (LIPA)/Connecticut Light and Power Company (CL&P) Long Island Replacement Cable Project (“LIRC” or “Project”) which extends from Norwalk, CT to Northport, NY in Long Island Sound. The Project involved the replacement of seven fluid-filled submarine transmission cables installed in 1969, with three new solid-core dielectric copper conductor cables.
The results included in this report are a component of the Monitoring and Mitigation Plan required by regulatory agencies overseeing the Project. The Connecticut Department of Environmental Protection (CTDEP) and the Connecticut Siting Council (CSC) have required CL&P to monitor the effect of the Project on the seafloor and shellfish resources by conducting an investigation after the completion of construction. The U.S. Army Corps of Engineers (USACE) also has a parallel requirement.
The study was performed in three previously established monitoring areas and designated reference area, as shown in Figure 1. This project was performed under contract with ESS Group, Inc. (ESS), on behalf of the LIRC owners and operators, as part of the monitoring program. Please refer to OSI Report #07ES077.5A (December, 2009) “Twelve-Month Post- Construction Seafloor Mapping Survey - A Component of the Benthic Monitoring Study for the Long Island Replacement Cable Project Summer 2009” for further information regarding project background and other aspects of the monitoring program.
The objective of this study was to measure the earth’s total magnetic field in the vicinity of the LIRC. This survey followed the same methodologies established for a previous study conducted in the same areas in November 2009 (OSI Report #09ES074). The results of these studies may be used in future modeling efforts, along with other information to estimate the local effect, if any, of the power cables as well as monitor changes in the detected magnetic fields over time.