The U.S. Navy awarded General Dynamics Nassco a $498.1 million contract modification to build a fourth Mobile Landing Platform ship of the USNS Montford Point class.

The Navy announced the award Dec. 19.

The 785-foot ship will be configured as an Afloat Forward Staging Base, which has a flight deck.

General Dynamics (NYSE: GD) Nassco will build the ship at its Barrio Logan yard. Some 70 percent of the work will be performed in San Diego, and construction is expected to be complete by March 2018.

The Naval Sea Systems Command of Washington, D.C., awarded the deal. The Navy bought its first three mobile landing platform ships as part of a package deal worth $1.3 billion.

In another Dec. 19 announcement, the Navy said that Nassco received a $7.3 million deal to decommission the Tarawa-class amphibious assault ship USS Peleliu by March. The Southwest Regional Maintenance Center in San Diego awarded the contract modification. With its large, flat deck stretching 820 feet, the Peleliu might be easily mistaken for an aircraft carrier.