The cracks in the vault of the tunnel between the Berri-UQAM and Saint-Laurent stations had been observed as early as April 13 “during a routine inspection”, 11 days before the long-term interruption on the metro’s green line .

This is what the Société de transport de Montréal (STM) admitted on Wednesday, in response to questions from La Presse, confirming by email “on April 13, during a routine inspection, a crack was observed in the vault of the intertunnel between the Berri-UQAM and Saint-Laurent stations”. The infiltration of water had also been noticed that day, 11 days before the announcement of the interruption on the green line.

The sequence should be specified here. First, on April 13, the STM said it had “communicated with the City to request that the water be cut off at this location in order to allow [him] to dry out the vault”.

Then, after a few days of “drying out”, an additional assessment was carried out, which “led us to the preventive measures we took on Monday, April 24, including the temporary closure of the green line between Lionel-Groulx stations and Frontenac,” said spokesperson Justine Lord-Dufour.

The STM does not specify, however, why a delay of 11 days was observed between the first observations of cracks and the first information made public, around 5 p.m. Monday. The shutdown, announced during rush hour, was to “allow a team of structural engineering experts to auscultate, hammer and observe” the degradation of the concrete, which ultimately turned out to be “superficial” , she recalls nevertheless.

“It is worth remembering that it is normal for there to be water infiltration in all types of underground installations, and we have a whole system in place to manage water in our network,” argues the passage Mrs. Lord-Dufour.

She recalls that the Company “carries out tunnel inspections regularly to observe the condition of the concrete in the vaults of the tunnels between the stations and in the STM stations”. “We have a method of inspecting the structure of vaults in metro tunnels in place for the past few years for the entire network,” she maintains.

To date, the STM says it does not yet know the exact cause of the observed water infiltration. An investigation is still ongoing. The reopening of the green line was announced Tuesday around 5 a.m., nearly 12 hours after the total interruption between the Frontenac and Lionel-Groulx stations, a section that serves around 150,000 people a day.

Emergency works, held overnight from Monday to Tuesday, “brought down the concrete that could have fallen by vibration on the track”.

Over the next few weeks, various preventive works will still have to take place above the tunnel in the coming weeks. A metal fence will be “installed over the next few nights to give us time to carry out work,” the STM said on Tuesday. “Permanent works” will then be undertaken to rebuild the vault as new, which is expected to take several months.

On Tuesday, the president of the STM, Éric Alan Caldwell, acknowledged that we should expect more construction sites of this kind in the metro, whose facilities are increasingly aging. “Major work needs to be done to give us another life cycle of the metro. And that’s what we’re going to do,” he said. “We must be aware that we have aging infrastructure, so we must continue our maintenance efforts,” also agreed general manager Marie-Claude Léonard.