STM detected cracks in green line tunnel 11 days before metro closure

Montreal's transit authority says the cracks inside the metro tunnel that forced the closure of a large portion of the green line on Monday were initially detected more than a week earlier.

During the afternoon rush hour, the Société de transport de Montréal (STM) shut down the metro between the Lionel-Groulx and Frontenac stations as a precautionary measure. The large downtown portion of the metro's green line was reopened to the public the following morning at 5 a.m.

The STM confirmed to CTV News that crews originally found the cracks in the arch of the intertunnel between Berri-UQAM and Saint-Laurent station during a routine inspection on April 13. The crews also observed water leaking from the fissures.

"It is important to remember that water infiltration is normal in all types of underground facilities and we have a system in place to manage the water in our network," said Isabelle-Alice Tremblay, an STM spokesperson, in an email. 

The transit authority asked the city to shut off the water to allow the vault to dry up.

The teams assessed the situation during a follow-up check on Monday, which led to part of the green line being suspended. Workers were able to remove part of the concrete that was prone to fall before resuming service Tuesday morning.

"As a preventive measure, a metal fence will be installed over the next few nights to give us time to do the work," Tremblay said, adding that, given the age of the metro infrastructure, it's normal for changes to occur in the concrete.

"Our teams of experts regularly observe and evaluate irregularities in the concrete of our infrastructures that do not compromise their integrity. When doubts arise, we push our technical investigations further and this is what was done in this case."

STM CEO Marie-Claude Leonard also acknowledged in an interview on Tuesday that part of the green line is aging, noting the Saint-Laurent station was opened in 1967.

She said the STM plans to spend $4.5 billion over the next 10 years to ensure the structures are safe.