Light rail consortium vows to get to bottom of incident that stranded 3 workers

A senior engineer for the consortium building Ottawa's $2-billion light rail line says they'll be looking into the cause of an industrial incident that required three tunnel workers to be escorted out by emergency crews on Thursday afternoon.

Peter Lauch, technical director with the Rideau Transit Group, told CBC News that a steel "cage" designed to provide stability and strength came loose from the tunnel wall as workers were applying shotcrete — essentially, sprayable concrete used to reinforce structures.

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Emergency vehicles raced to Laurier Avenue and Waller Street just before 4:30 p.m. on reports of what was initially described as a tunnel collapse.

One worker had to be taken to hospital with a hand injury, while two others were unhurt.

In audio from the dispatch calls, provided by Broadcastify, an emergency responder warned "the side of the wall is caving in" where the three workers are trapped, and that "there could be additional injuries as this thing continues to evolve."

Lauch said workers have "done a lot of shotcrete work already" at LRT construction sites, particularly at Lyon Station, which is west of Thursday's tunnel incident.

"It's sort of standard operating procedure," Lauch said approximately three hours after the incident.

"It's definitely something, obviously, that we're looking into."

A stretch of Laurier from Nicholas Street to King Edward Avenue was shut down for nearly two hours as the three workers waited underground.

Lauch said two of the workers were likely in the basket of a hydraulic boom lift when the steel cage peeled away from the wall, which may have somehow interfered with their ability to lower the lift.

"These boom lifts — it's not unusual for the hydraulics to fail and for guys to get stuck up there. You wait until someone brings you a ladder," he said. "I'm assuming that's what happened, but that's speculation on my part."

Tunnel 'structurally sound'

City officials downplayed the severity of Thursday's incident, with John Manconi, the general manager of transportation services department, calling it a "minor construction incident" in a statement.

Lauch said he had no concerns about the structural integrity of the tunnel itself.

"The tunnel itself, it's structurally sound. This is the final layer, a small layer of concrete that's being put on top of that," he said.

"It's engineered, it's a proven design, and we'll have to investigate what happened now."

Ontario's Ministry of Labour has also been called in to investigate the cause of the incident.