Anticipating a conflict with the construction of a floating dry dock at Electric Boat’s facility in Groton, the Navy is planning to relocate an underwater cable and sensor array in the Thames River that is used to analyze and neutralize a ship’s magnetic field.

The Navy has held several meetings with local stakeholders as it examines alternatives locations for the underwater electromagnetic measurement system and a data concentrator shed located on pilings across and adjacent to the river channel just south of EB.

The system is used by the Naval Submarine Base to determine whether degaussing, or magnetic silencing, is needed on submarines or ships. Steel hulled ships are surrounded by a magnetic field that changes as the ships move across the globe, which has natural magnetic fields between the North and South poles.

The system checks ships to ensure the magnetism present in the hulls does not trigger magnetic mines or make ships easier to detect.

The Navy is in the draft phase of an environmental assessment of the project.

Submarine base spokesman Chris Zendan said it is ultimately the Navy’s decision on the final location and that decision will be based on factors that include “potential impacts to the physical and natural environment.”

A fact sheet provided by the Navy about the project shows construction taking place at two possible locations 2,000 to 2,500 feet south of the existing site. The older shed and sensor array will be removed once the new one is completed.

A range control building at Fort Trumbull State Park would not be moved.

The project includes installation of new data and power cables in the riverbed, stretching from the range control building at Fort Trumbull to an 18-by-18-foot structure atop pilings just south of the Buckeye Terminal Pier in Groton.

The existing shed and sensor array are located further north and closer to EB, which announced last year its plans for a $850 million project to expand and improve its Groton shipyard, including a new construction bay to accommodate the Columbia-class ballistic missile submarines.

The new sensor array would be installed across and centered on the channel in a 13-foot-deep trench, with 500 feet long cable with sensors. The construction is expected to take six to eight months and followed by demolition of existing structures.

If a finding of no significant impact is reached, Zendan said the environmental assessment would be concluded by August 2020 and a contractor enlisted for the work by November.

Stakeholders will be updated as the project progresses. The last meeting on Dec. 20 involved Gateway, operator of State Pier in New London, along with Cross Sound Ferry, Buckeye, a representative from the state office of Military Affairs and New London city officials. Zendan said that meeting of the Thames River Maritime Workgroup was organized by the Connecticut Port Authority.

A preferred alternative to the location of the equipment has not yet been determined.

The Navy said it is consulting with the U.S. Army Corps of Engineers, U.S. Coast Guard and U.S. Environmental Protection Agency, among other state and federal agencies.

g.smith@theday.com