AUGUSTA – Members of Bath Iron Works’ largest union overwhelmingly approved a four-year contract that gives workers annual 3.5 percent to 4 percent pay hikes while increasing pension contributions and holding the line on health care contributions.

Members of Local S6 voted in favor of the contract by a 2-1 margin Sunday afternoon at the Augusta Civic Center, said John Carr, spokesman for the Machinists union, the parent of the S6. He declined to give a specific tally.

The vote came just hours before the existing four-year contract was due to expire at midnight.

The union, the largest at BIW, represents about 3,400 jobs that include mechanics, fitters, welders, painters and electricians.

The contract gives workers pay hikes of 3.5 percent in year one, 3.8 percent in years two and three, and 4 percent in year four. It also calls for increased pension contributions while employees’ contributions to health care coverage will stay the same, Carr said.

“It’s a very good economic package, especially in the shaky economic environment this country’s in right now,” he said.

The local union has been in turmoil since being placed in receivership in March by the international union after accusations including financial improprieties and pornography on computers. Last month, a committee appointed by the international union held hearings to determine the fate of the union and its leadership.

In response, four leaders from the local BIW union sued the parent Machinists union, accusing it of carrying out a vendetta against local officers.