Late Thursday, Feb. 20, crews using a roadheader machine to dig the tunnel noticed debris falling from above. Workers and equipment were pulled from the scene before the collapse occurred directly above where work was taking place on Waller Street, south of Laurier Avenue.
Rideau Transit Group (RTG), the contractor building the line, said geotechnical engineers were on site assessing ground conditions in the area. RTG said monitoring equipment has confirmed that the impact is localized and the geotechnical team has not identified any safety concerns.
City of Ottawa crews succeeded in patching the hole Saturday, while RTG crews worked to stabilize the tunnel face. The collapse comes just two weeks after project stakeholders celebrated reaching the 10 percent completion mark in tunnel construction for the project.
While work is suspended at the collapse location, work on the project continues at the other two tunnel construction locations at Queen and Bay streets and Queen and Kent streets.