It's not clear how long it will be before tunnel boring for the Confederation Line of the light rail transit project will be able to resume.
A section of the road on Waller Street at Laurier Avenue caved in around 1 a.m. Friday and left a hole 40 feet deep and 25 feet wide.
Overnight construction crews were at work using one of the tunnel borers when they noticed material falling at the entrance of the tunnel; they pulled out before the collapse, which has not damaged the tunnel itself.
Deputy City Manager of Planning and Infrastructure Nancy Schepers says their sole focus now is securing the site.
"There's experts on site as we speak, who are doing a thorough investigation to understand what the root cause is," she said at a technical briefing at City Hall. "Following that, there will be a plan put forward in terms of how [Rideau Transit Group] would proceed with tunnelling."
Crews are still not sure what the root cause of the collapse is. The ground at this site is softer than at the West Portal and Central shaft, where the road headers have reached bed rock.
The Rideau Transit Group says the loose ground at the Waller site has been stabilized, and engineers were immediately called in to investigate.
"At this point again, this is soft soil that we're mining through," says Tim Stewart with the Rideau Transit Group. "Our experts are on site every day, on any advancement that we determine what the support is going to be, how often we're going to support it ... We're in the early stages of trying to understand what happened today."
"We monitor everything around it," he adds. "We're monitoring the buildings around it, we monitor the roads around it, so we're consistently trying to determine if there is any other settlement and how we'll mitigate those impacts."
Water was shut off to the apartments at 50 Laurier East while work was being conducted to repair a water main that broke during the road collapse.
RTG will likely pick up the tab for repairs.