The contract is tied to the 7,200-lane Midnight Sun and North Star (both built 2003), which currently service a loop that links Tacoma, Washington to Anchorage, Alaska.

The shipyard says the economic and environmental benefits of LNG power has made related technologies desirable for a variety of newbuilding and conversion projects.

In a statement it told investors the deal, coupled with TOTE’s recent order for a pair of LNG-powered containerships, “validates” it reputation as one of the nation’s leading shipbuilders.

The financial terms of the transaction and the timeline attached to the project were not disclosed in Monday's filing.