LRT tunnel inspection reveals pieces of concrete chipped from main slab, city says

The city's infrastructure department says pieces of concrete separated from the main slab causing debris to fall along train tracks at St-Laurent station — which resulted in a partial shut down of the light rail train service and a tunnel safety inspection on Tuesday.

As of about 5 p.m., OC Transpo said light rail trains would be safe to begin running normally, after it had suspended train service from Blair to Hurdman stations for most of the work day.

The interruption was necessary to conduct a "structural inspection" of the tunnel, the transit agency said.

In a memo to council, OC Transpo head Renée Amilcar said the safety inspection was initiated "out of an abundance of caution," and that there are no issues with any of the LRT trains or system. 

Later in the afternoon, Amilcar said the inspection was complete and it is now "safe to resume service in the St-Laurent tunnel."

Amilcar said the city's infrastructure and water services department were inspecting the tunnels as it maintains the infrastructure.

'Delamination' issue caused chipping 

The city's acting general manager for infrastructure, Carina Duclos, issued a memo late Tuesday evening outlining how staff responded to the concern. 

Duclos said following a preliminary assessment, the department hired a structural engineering firm to conduct a detailed inspection of the tunnel area.

"Results from the inspection confirmed delamination," Duclos stated, explaining that means a "separation of the paste layer at the surface, creating an unbonded layer with the main slab." 

With direction from the structural engineer, Duclos said, a contractor conducted "sounding and scaling" to remove small, concrete pieces that had separated from the main slab. That work wrapped up at about 4:15 p.m., she said, and the structural engineer report deemed that there were "no hazards" and it was safe to resume service.

Duclos goes on to explain that the St-Laurent bus station was constructed in the mid 1980s, and that it now houses both the LRT tracks in the tunnel below — consisting of a "series of single span concrete rigid frame structures" — and the upper level platform.

"It is not uncommon to see delamination and scaling required in a structure of this age and with this level of complexity," she wrote.

The infrastructure department will conduct routine condition assessments of the structure in collaboration with OC Transpo, Duclos continued.

Replacement buses no longer running

Train service between Hurdman and Blair stations had been suspended since Tuesday morning for that "structural inspection" at St-Laurent station.

R1 replacement buses were running between Blair and Hurdman stations instead of trains. There were also shuttles running connecting Cyrville to St-Laurent stations.

Shortly after 5 p.m., Amilcar said full train service is running regularly, and replacement buses will be wrapping up shortly. 

A 2022 public inquiry found the Confederation Line was rushed into service to open in September 2019.

It's had multiple problems, including chronic axle problems that have caused derailments and led OC Transpo to scale back on the number of trains in service as it works on solutions.

Expansion to the east, west and south was originally supposed to be all done by 2023. None of those new lines have opened, with delays pushing them back to this spring, 2025 and 2026.