The US Navy’s Portsmouth Naval Shipyard (PNS) has opened its new Dry Dock 1 Super Flood Basin under the Shipyard Infrastructure Optimisation Programme (SIOP).

A ceremony to mark the opening of the newly constructed dry dock was held on 5 May at PNS in Maine.

Dry Dock 1 is the shallowest of the three dry docks at the PNS shipyard. It impounds more than 20 million gallons of water at a 16ft differential from the Piscataqua River.

Earlier, the Dry Dock 1 required a buoyancy assist system consisting of a large floodable air-filled tank and a peak high tide to dock and undock the submarines.

With the new Super Flood Basin constructed at the entrance of the dry dock, the submarines can dock without buoyancy assist system and high Piscataqua River tides.

The Los Angeles-class nuclear-powered attack submarine, USS Cheyenne (SSN 773), recently docked at the newly constructed basin.

USS Cheyenne commanding officer commander Samuel Bell said: “This milestone is the culmination of significant effort and represents the dedication of both the Navy and the shipyard to the Los Angeles-class service life extension programme.

“Cheyenne is setting the standard for engineered refuelling overhaul excellence to benefit the follow-on submarines that will be the backbone of the fleet for decades.”

Construction of Super Flood Basin is one of the four projects under the SIOP effort to update and modernise the US Navy’s four public shipyards.

The programme is supported by the US Naval Sea Systems Command (NAVSEA), Navy Installations Command (NIC) and Naval Facilities Engineering Systems Command (NAVFAC).

Following the opening, a new phase of SIOP will soon bisect the basin to create two additional dry docks, thereby completing the planned $1.7bn effort to upgrade and expand the shipyard.