By Colin A. Young
State House News Service

An electrical cable under Boston Harbor that has been the source of delays for a dredging project required before new supertankers can dock in Boston will be removed and replaced, the result of a federal court settlement that clears the way for the Boston Harbor Deep Draft Navigation Improvement Project.

The U.S. Army Corps of Engineers and Massachusetts Port Authority are pursuing a $310 million project to carve out a deeper channel in Boston Harbor, making the port accessible to the larger class of ships now able to fit through an expanded Panama Canal and already serving deeper ports.

But a cable laid in 1990 to bring power to the Deer Island Wastewater Treatment Plant was installed closer to the seafloor surface than allowed by a U.S. Army Corps of Engineers permit and would pose a danger to people and equipment dredging the harbor, according to the suit filed by the federal government and MassPort.

Last week, the Massachusetts Water Resources Authority and Eversource settled the suit filed against them over the cable that spans two of the harbor's shipping channels, the U.S. Attorney's Office announced, an outcome that will allow the dredging to move ahead.

“The Deep Draft project is necessary to keep the Port of Boston and its shipping facilities competitive with other East Coast ports,” William Weinreb, acting U.S. attorney for the district of Massachusetts, said in a statement. “The settlement also means there will be no interference with the provision of electricity to the Deer Island Waste Water Treatment Plant, which is critical to keeping Boston Harbor clean. This is a victory for both the local economy and the environment.”

The Deer Island facility was built by the Massachusetts Water Resources Authority (MWRA) as part of the effort to clean up Boston Harbor. The MWRA now serves 2.5 million people, supplying 215 million gallons of water and treating an average of 350 million gallons of sewage daily.

The settlement requires Eversource to install a new cable connecting the K Street substation in South Boston to Deer Island and have it powered by Dec. 31, 2019. That cable is expected to cross land in South Boston, cut through MassPort's Conley Terminal, and enter the harbor just north of Castle Island. It is to be laid at least 75 feet below the low-water line.

The existing and improperly installed cable is to be de-energized by Feb. 28, 2020, per the settlement, and the 1.4-mile section closest to the container terminal is to be removed by May 31, 2020. The settlement allows the other portion of the cable to be abandoned in place if the various permitting agencies allow it.

“We're pleased to have reached a resolution with all parties that permits us to continue providing safe and reliable service to MWRA, while also accommodating the moving forward of the Massport/ACOE harbor dredging project,” Eversource spokesperson Rhiannon D'Angelo said in a statement.

D'Angelo said Eversource is still working to determine the cost of installing a new cable and removing the old one, and expects to file its plan with the state Department of Public Utilities later this summer.

"Once the cost recovery is approved by the DPU, we'll recover the cost from the MWRA, Harbor Electric Energy Company's sole customer," she said, referring to the Eversource subsidiary that powers Deer Island.