Bath Iron Works employees celebrate the christening of the USS Harvey C. Barnum Jr., the shipyard’s 40th Arleigh Burke-class destroyer, on July 29. Jason Claffey / The Times Record

Bath Iron Works’ largest union this weekend will vote on a contract proposal that includes the biggest pay raises the union has ever been offered — but there is a hitch.

Machinists Union Local S6 represents about 4,250 of the shipyard’s 6,500 workers. Union representatives this week announced they reached a tentative agreement with BIW on a new three-year contract, which includes pay raises of 4%-9.5% the first year, 5% the second year and 4% the third year. They are the biggest pay raises by percentage ever offered to the union, which was founded in 1955. The old contract included annual 3% pay raises.

“It’s historic,” Local S6 spokesperson Devin Ragnar said. “No member has seen percentage increases like that.”

Some of the pay hikes would be partially offset by annual health insurance premium increases of about 4% for the three plans offered. Deductibles would also be raised for some plans. Union representatives also agreed to the elimination of an unpaid week off for members at the end of December. If the contract is approved, that would become a normal work week, though the shipyard plans to offer members four unpaid, excused days off during that time, according to Ragnar.

Contract voting opens Friday and ends at noon Sunday. Members will be asked if they approve the contract and if they authorize a strike in the event the contract is rejected. A simple majority is needed to ratify it. A two-thirds majority is needed for the strike authorization. If that fails, the contract would be ratified regardless.

Ragnar said while workers appreciate the potential pay raises, some have voiced displeasure, saying the pay hikes should have been higher due to factors like inflation. He said another common criticism is the elimination of the end-of-December week off.

“The Negotiation Committee believes it is the best proposal they could bring back to the members,” the union said in a statement. “Therefore, we recommend it.”

BIW officials said negotiations have been “professional and respectful.”

“The substantial wage and benefits package is a clear indication that our company believes in its current workforce and wants to continue to attract new talent to sustain our work into the future,” BIW said, emphasizing “the importance of building on the momentum in the shipyard and seeking continuous improvement.”

The shipyard agreed to increase 401(k) matching contributions from 35 cents a dollar up to 5%, to 40 cents in 2025 and 45 cents in 2026. It also agreed to offer a Roth 401(k) starting in 2024.

During the last contract negotiations in 2020, the union held a two-month strike over disagreements about BIW’s use of subcontractors and planned changes to seniority. The two sides quickly agreed to the subcontracting provision this time around.

The 2020 strike, combined with the coronavirus pandemic, put BIW months behind schedule building Arleigh Burke-class destroyers, the only vessel it builds. BIW President Chuck Krugh said production has increased in recent months. The shipyard earlier this month was awarded a Navy contract to build three more Flight III Arleigh Burke-class destroyers. Twelve destroyers are now in the works at the shipyard.

Ragnar said contract talks this year were more productive compared to 2020 because both sides “kept the process running smoothly and operating more professionally.” The leaders of the two sides are different from 2020; Krugh replaced Dirk Lesko and Local S6 President Chris Williams replaced Chris Wiers.