A few residents have inquired regarding the resumption of tunneling for Ottawa’s Light Rail Transit (LRT) following the sinkhole which appeared on Sussex and Rideau Street June 8. I now have an update on this.
Based on the results of extensive investigations, Rideau Transit Group (RTG) will proceed in phases with the excavation of the final 50 meters of tunneling. They will be implementing additional precautions and monitoring to ensure safe tunneling.
Phase 1 is comprised of approximately 10 metres of tunneling starting at Rideau Station cavern and will move westerly. This area is located approximately 30 metres from the eastern-most edge of the sinkhole. It has been confirmed that soil was not disrupted in this area.
Phase 2 of tunneling is comprised of approximately 22 metres of tunneling located in an area closer to the sinkhole. Investigations have confirmed that soil conditions have changed in this area since the infrastructure failure. The tunnel will be stabilized with additional drainage and grouting. A pipe roof system will be installed to reinforce the roof of the tunnel.
Phase 3 is an area of the tunnel located beneath the sinkhole, approximately 18 metres in length. Ongoing investigation work during the tunneling process will help to inform the implementation of appropriate design measures for the reinforcement of the tunnel.
The tunnel is being constructed by a consortium that includes Dragados Canada, one of the largest private-public contracting firms in the world who worldwide tunnelling expertise with more than 857 miles of tunnels in all types of geological conditions.
The Rail Implementation Office, along with independent engineering experts, is conducting an investigation to review the infrastructure failure that occurred. The cause analysis of the road collapse is ongoing and updates will be provided once the review is complete.