Eversource to lay new cable under Boston Harbor to keep Deer Island running and to let the feds dredge a channel for bigger ships

The Department of Justice says it's settled a lawsuit against Eversource and the MWRA over a Deer Island power cable under Boston Harbor the government had said was not buried deeply enough to allow for planned dredging to let the Conley Terminal in South Boston handle larger ships.

Under the settlement, an Eversource subsidiary will install a new cable from a South Boston substation to Deer Island to power the MWRA's sewage treatment plant - outside of the Reserved Channel and away from the channels to be dredged as part of the $310-million "Deep Draft" project - by the end of 2019. The company will then remove the existing cable.

The Justice Department filed its suit last year on behalf of the Army Corps of Engineers. Massport, which runs the container terminal, then joined the suit against Eversource and its fellow state authority.

When the then Boston Edison won federal permission to install the cable in 1990 to feed the MWRA's new treatment plant on the other side of the harbor, it agreed to bury the cable at least 25 feet under the bottom of the harbor. In its suit, the government charged the cable was, at some points, just 12 feet below the bottom.

Under the settlement, Eversource will pick up the full tab for the cable replacement.