The Navy has awarded Bath Iron Works a contract modification worth $59.4 million to provide engineering and technical assistance in building new Arleigh Burke-class guided missile destroyers, U.S. Sens. Susan Collins and Angus King announced Wednesday.

The expanded contract funds a variety of services and design improvements related to the Flight III upgrade, which adds an air and missile defense radar to the DDG-51 class ships, according to Navy reports.

BIW is in the midst of a building boom as crews work on the final two destroyers in the three-ship Zumwalt class as well as four more Arleigh Burke-class guided missile destroyers. While at least three additional Arleigh Burke destroyers will be built in Bath as part of a multi-year contract awarded by the Navy in 2013.

Collins is a member of the Senate Defense Appropriations Subcommittee and King is a member of the Senate Armed Services Committee.