MONTREAL -- Montreal was lucky things weren’t worse this July when, we’ve now learned, explosives suddenly went off in the Mount Royal Tunnel.

The explosives were a century old and came as a surprise to workers for the REM light rail project, which was underway in the tunnel at the time.

No one was injured, but drilling came to a halt—and it hasn’t started up again since in the same way, as it’s been done from a distance now.

This is one of the reasons the REM’s opening will be delayed, authorities now say. The final completion date for the entire network is now scheduled for the end of 2024, a year behind what was originally planned.

Since the explosion, “the work has been suspended, and it's only been a few days since [when] work has been completed,” said Macky Tall, the CEO of CDPQ Infra, which is in charge of the project.

“We have been able to update all the construction work and procedures and…we are able to restart.”

Another delay comes from a portion of the future line between Central St. station and Du Ruisseau—that will be pushed back until 2023.

For commuters using the Deux-Montagnes train line, this all adds up to more time spent on bus shuttles and the metro.

“Those interim measures we have put in place in the meantime are working well and are providing a very diligent delivery [and] transport service to these customers,” said Tall.

Every other line on the light rail is also behind schedule to varying degrees, with officials saying COVID-19 has slowed construction in general. 

The yearlong delay will likely mean significantly higher costs, but Tall says management is working to contain that as much as possible, “as we have from day one of this project.”

And the province won't be footing the extra bills. A spokesperson for Transport Minister Chantal Rouleau has confirmed the government’s portion will remain at $1.28 billion and any cost overruns will be the Caisse’s responsibility.

In terms of progress, there is some: four REM passenger trains have already arrived, and testing the network on the South Shore is expected to begin this fall.