The St Lawrence Seaway — the Great Lakes’ ports only shipping passageway to the Atlantic Ocean and international trade — reopened on Monday after a union and employers struck a tentative labour deal on Sunday.

The critical waterway for bulkers, tankers and other cargo vessels closed on the night of 21 October when workers on the seaway’s Canadian side began striking against St Lawrence Seaway Management Corp (SLSMC), which manages 13 of the 15 locks on the US-Canadian system of canals.

Unifor, which represents 360 workers, gave a 72-hour notice to strike on Wednesday.

The agreement will have to be ratified by employees in the coming days, but ships have had access to the seaway and the locks since 1100 GMT on Monday as employees returned to work at that time, the SLSMC said.

“We have in hand an agreement that’s fair for workers and secures a strong and stable future for the Seaway,” SLSMC chief executive Terence Bowles said in a statement on Monday.

“We know that this strike has not been easy for anyone, and value the patience and cooperation of our marine industry binational partners; carriers, shippers, ports, local communities and all those who depend on this vital transportation corridor on both sides of the Canada-US border.”

Details of the tentative agreement will first be shared with members and will be made public once an agreement is ratified, Unifor said. A vote will be scheduled in the coming days.

Unifor had last gone on strike 55 years ago, national president Lana Payne said in a statement on Monday.

“They did so to fight for a more respectful workplace and for an agreement that reflects today’s economic times,” she said.

“They have shown that the best deal is reached at the bargaining table, and I congratulate the committee on their outstanding work on behalf of their members.”

The tentative agreement covers Unifor members in Ontario and Quebec, who work in the supervisory and engineering group and the maintenance, operations and clerical group, the union said.

“I am so proud of the unity of our members along the Seaway as they joined together to secure better wages and working conditions for all,” Unifor Quebec director Daniel Cloutier said in a statement on Sunday.