Montreal Metro's Green Line resumes service after work on cracks in tunnel ceiling

The Montreal Metro's Green Line is up and running Tuesday morning, a day after engineers uncovered cracks in the tunnel's vaulted ceiling, according to Montreal's transit authority.

The service was shut down just as the afternoon rush hour was getting into full swing Monday, forcing passengers to find other ways home, such as shuttle buses and the Orange line.

The Société de transport de Montréal (STM) said in a statement Tuesday morning that their experts confirmed "it is safe to resume service between Lionel-Groulx and Frontenac Metro."

As of 5 a.m. this morning, De Maisonneuve Boulevard between the intersections of Berri and Saint-Laurent streets had also reopened.

A team of experts assessed the vault of the tunnel for over six hours between the Saint-Laurent and Berri-UQAM stations last night and found that "the degradation of the concrete is superficial and the integrity of the vault is not in question,"  the transit authority said in a statement. 

However, the STM says it will install a metal mesh in the coming days as a preventive measure to allow crews to carry out repairs.

The suspension of service a was a "preventive measure," said STM CEO Marie-Claude Léonard on Radio-Canada's Tout un matin.

Workers had noticed cracks in the tunnel ceiling following a water leak days ago, she said, and although water leaks in the Metro are typical, the fissures were cause for concern.

"When there are employees who have to go to work on the track, we have to make sure we have a section where we can completely cut off the power supply without any risk to our employees," she said. 

The STM said in a statement that a plan to inspect the structure of the metro tunnel vaults has been in motion for the past few years and work is ongoing.