BATH — Bath Iron Works has notified one of its unions that it plans to cut up to 250 jobs as design work slows down on the next-generation Zumwalt destroyer.

The shipyard today notified the Bath Marine Draftsmen’s Association of the layoffs to be effective on June 24. It follows the layoffs of 130 designers in January and 130 workers engaged in construction the following month.

Spokesman Jim DeMartini says the shipyard has to balance its work force with the available workload in a period in which the Navy is buying fewer ships.

Sen. Olympia Snowe says the Navy needs to build up its fleet. She says that as of May 31, the Navy claimed a force of just 285 ships, far below the 313-ship minimum established by the Navy.