A sinkhole, measuring about eight metres wide and about 12 metres deep, has forced authorities to close roads in Ottawa

Sunday, February 23, 2014

A sinkhole, measuring about eight metres wide and about 12 metres deep, has forced authorities to close roads in Ottawa

Ottawa Citizen

Giant sinkhole forces closure of roads, transit station in Ottawa

By The Canadian Press February 21, 2014

A sinkhole opened up near the University of Ottawa at Laurier Avenue and Waller Street in Ottawa on Friday, February 21, 2014.

Photograph by: Justin Tang , Ottawa Citizen

OTTAWA — City crews are at the scene of a massive sinkhole that has opened up in Ottawa.
The sinkhole, which measures about eight metres wide and about 12 metres deep, has forced authorities to close roads after the hole opened near the intersection of Laurier Avenue and Waller Street in downtown Ottawa.
The hole is also causing major delays for commuters as OC Transpo had to shut down a nearby transit station.
City workers at the site say they don’t yet know the cause of the collapse.

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Road collapse leaves 8-metre wide sinkhole at tunnelling site

24-hour work by Rideau Transit Group began Wednesday for light rail transit system

CBC News Posted: Feb 21, 2014 9:57 AM ET Last Updated: Feb 21, 2014 8:21 PM ET

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Road collapse halts LRT tunnelling 2:45
A sinkhole eight metres wide and 12 metres deep opened up at the construction site where crews are digging the eastern entrance to Ottawa's light rail tunnel, and officials are trying to determine why.

Crews work on a large sinkhole that halted tunneling work on the East Portal of Ottawa's LRT project. (Fred Chartrand/Canadian Press)

No one was injured. It happened on Waller Street, just south of Laurier Avenue, and tunnelling operations at the site have stopped.

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A digging crew in the tunnel first noticed dirt falling into the tunnel at about 10 p.m. ET Thursday, where the excavator — a roadheader called Crocodile Rouge — was gouging the earth, said deputy city manager Nancy Schepers during a technical briefing on Friday.
"As they continued to observe material entering the tunnel, and the rates increased, the crew suspended tunnelling operations and immediately notified [Rideau Transit Group's] management to discuss next steps and a stabilization strategy. City staff were also notified at that time," Schepers said.

By 1 a.m., a large sinkhole had opened up on Waller Street.

"We can only confirm that it was directly above where tunnel excavation was occurring, and at this point we cannot confirm its root cause," Schepers said.

Soil conditions in area of collapse 'challenging'

This sinkhole formed early Friday after a road collapse in downtown Ottawa. (Photos courtesy of John Holtby and Brian Bancroft)

RTG crews had begun 24-hour tunnelling operations on Wednesday. Schepers said the city and crews were aware that soil conditions were different in the area.
"We were aware of different geotechnical conditions in this vicinity, and some of you will recall that before we went out to tender we actually shortened the length of the tunnel, recognizing that this type of material would be challenging. Certainly we provided all that geotechnical data," Schepers said.
"Monitoring equipment has confirmed that the impact is localized, and the geotechnical team has not identified any safety concerns at this point."

The Crocodile Rouge roadheader is about 20 metres away from solid bedrock that two other excavators are working on, in different sections of tunnel, elsewhere in Ottawa.