The U.S. Navy has awarded General Dynamics‘ (NYSE: GD) NASSCO subsidiary a $324.4 million contract modification for the detail, design and construction of a follow-on Expeditionary Sea Base.

The modification also definitizes the procurement of long lead-time materials needed to build the ESB 5 ship, the Defense Department said Thursday.

NASSCO will perform majority of the work in California and the rest in Pennsylvania, Virginia, Texas and Louisiana through May 2019.

ESBs are designed to feature a flight deck and expansive reconfigurable mission deck; small craft launc-and-recovery platforms; command, control, communication, computer and intelligence systems; and military personnel accommodations.

Navy Secretary Ray Mabus redesignated the Mobile Landing Platform Afloat Forward Staging Base as ESB in September last year.

The vessel will be a key element of the critical access infrastructure that works to help the military branch deploy forces and supplies during missions.