Skipped inspection, warning signs preceded falling concrete in LRT tunnel
City didn't complete scheduled inspection of St-Laurent tunnel in 2022, says compliance officer
Parts of the concrete tunnel at Ottawa's St-Laurent LRT Station were showing signs of "severe" — and sometimes "very severe" — cracking and chipping back in 2020, but internal documents obtained by CBC News suggest some of those problem areas labelled "urgent" weren't patched up until chunks of concrete fell onto the train tracks in January.
According to an independent compliance officer, the city didn't fully inspect the tunnel again in 2022 when it was due for another checkup.
On the morning of Jan. 2, OC Transpo partially shut down LRT service after it noticed pieces of concrete had fallen from the tunnel onto the tracks at St-Laurent station. At the time, the city's infrastructure department blamed "delamination," when layers of concrete separate from the main slab.
Officials said the deterioration was "not uncommon" for a structure that dates back to the 1980s when the tunnel was used as a bus transitway before being converted for the LRT Confederation Line.
Internal transit department emails and inspection reports obtained by CBC through a freedom of information request reveal the city had hired engineering firm Morrison Hershfield to oversee the tunnel inspection and fix any issues.
On the afternoon of Jan. 2, a senior structural engineer with the company noted the team removed "loose concrete" over the westbound LRT track in an area known as "Joint G," where the debris fell from. The team also performed minor "scaling" in another area over the eastbound track — a term used to describe both the flaking of a concrete surface and the job of removing loose pieces.
Emails sent over the following weekend show contractors inspected the tunnel again and removed more concrete from areas where it posed a hazard, including a "significant location of concern" that had previously been identified in the city's 2020 inspection report.
"There is another delamination next to this one, as well. We were able to reach both locations and perform some scaling to knock off the loosest pieces," the engineer wrote, adding that he wanted to return two days later to perform more scaling and other work on "deteriorated" areas he didn't have time to address on the weekend.
The engineer added they'd bring a "heavier chipping tool" to remove more material.
Scaling concrete 'urgent': report
In the October 2020 inspection report obtained by CBC, inspectors noted "spalls, delaminations and cracks with efflorescence" (water stains), as well as an "active leakage" in that Joint G area. Similar concerns were noted on the bus terminal platform above that section, and included a "corroded cover plate," "perforated" steel curb armouring, wide cracks and spalling.
Spalling is the weakening of a concrete surface over time and can be caused by moisture or the corrosion of embedded steel, causing pieces to chip away.
The inspection also identified some "very severe" delamination, spalling and cracks ranging from narrow to wide along other areas of the LRT tunnel that year.
At the time, inspectors recommended repairing the concrete — specifically, scaling areas of delamination — over a timeframe of one to five years.
The inspector categorized the recommended concrete repairs as "minor rehabilitation," but wrote "urgent" under the maintenance timing category.
Engineer Solomon Tesfamariam explained to CBC that such signs of external deterioration are expected in a concrete structure that's 37 years old, and which has been exposed to severe environmental conditions like those experienced during Ottawa winters.
"It's not really safety [or] critical issues, more [an] operational issue to increase the service life of the asset," explained Tesfamariam, a professor at University of Waterloo who specializes in structural engineering and infrastructure.
RTM requested risk assessment
Emails also show the group in charge of maintaining the Confederation Line, Rideau Transit Maintenance (RTM), raised concerns about the condition of the tunnel infrastructure, which falls under the city's responsibility, questioning how safe it was for their workers.
"After the incident ... RTM and [train maker] Alstom have some concerns about the condition of the 'legacy structures' as the case of this portion of tunnel,'" reads a Jan. 3 email from RTM's general manager to the city's engineering director.
"The removals of concrete pieces have mitigated the immediate risk ... but our concern is whether other areas of the tunnel could pose a risk to our staff," the RTM manager wrote.
The manager then requested a risk assessment, and asked the city for tunnel inspection records to see if they were "up to date and any risks found during those inspections have been suitably mitigated."
In fact, inspections weren't up to date because the city deferred a full inspection of the tunnel in 2022, according to the light rail regulatory monitor and compliance officer.
2022 inspection skipped
Ontario's Ministry of Transportation (MTO) requires tunnel inspections every two years under its Ontario Structure Inspection Manual (OSIM).
Under the project agreement in Ottawa, LRT tunnel inspections fall to LRT builder Rideau Transit Group and RTM, except for the St-Laurent tunnel which is under the city's jurisdiction.
The compliance officer found the city performed an inspection of one of the four areas that make up the St-Laurent station, but deferred the remaining three until sometime in 2024 "due to the major rehabilitation work" at the adjacent bus terminal. That work wrapped up late last year.
The MTO allows deferrals for major rehabilitation, according to its guidelines from 2009.
It doesn't inspire confidence.- Coun. Shawn Menard
During a transit commission meeting last Thursday, the city's linear asset manager Scott Laberge confirmed that in 2022, the city skipped inspecting the areas from where concrete debris had fallen.
Laberge told the commission he wasn't sure if the city would have caught the issue had it fully inspected the tunnel two years ago.
"It's tough to say, chair, when the issue would have occurred," Laberge said in response to Coun. Shawn Menard, who raised concerns over the lack of inspection. In an email dated Jan. 7 and obtained by CBC, Laberge was sent a copy of the 2020 inspection report.
"If the delamination would have been present at the time of a 2022 inspection or if it would have happened after that inspection, it's really tough to say," said Laberge at commission.
But in a statement to CBC, the city explained that throughout the rehabilitation project from 2022 to December 2023, it "monitored" some of the other areas listed in the 2020 report that needed scaling "with no changes identified that would warrant immediate action."
WATCH | 'Tough to say' when loose concrete issue began, says asset manager:
Menard told CBC he was surprised to learn the inspection four years ago may have identified a "precursor" to the incident.
"[It] makes me question why there wasn't work done to rectify it [earlier]," he said. "It doesn't inspire confidence, and it's something that the city needs to take very seriously going forward if we're going to get riders to take transit and feeling safe."
Tesfamariam, the engineer, warned against the "waterfall effect" of aging infrastructure, which can degrade more quickly and cost more and more to fix without constant maintenance.
"Skipping [inspections] might not be a good idea, but at the same time, skipping it might be the necessary operational requirements because there are other pressing needs," he explained. "So it's a balancing act between safety and operational costs."
The city declined an interview, but said in an emailed statement attributed to Laberge that a structural engineer did perform a "comprehensive" inspection of the tunnel in response to RTM's concerns, and deemed any hazards to have been "successfully mitigated."
"The work required to address the areas listed in the 2020 OSIM report is complete," Laberge wrote.
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