TORONTO—The City of Toronto is planning to hire Clearway Construction Limited to extricate a micro- tunnelling boring machine that has become ensnared in steel tiebacks in a tunnel on Old Mill Drive.
A report being considered by Toronto’s General Government Committee today called the situation “a matter of extreme urgency, as there was a significant health and safety hazard to the public.”
The value of the non-competitive contract to be offered to Clearway was set at $9 million.
According to a city report, the boring machine was being used to construct a new 900-millimetre diameter storm sewer along Old Mill Drive. The steel tiebacks had been used to brace shoring from two mid-rise development excavations.
The report said the integrity of the roadway, nearby subway tunnel and surrounding infrastructure was undermined as a result of ground movement around the boring machine due to excessive ground water and poor soil conditions. The ground instability further led to the creation of a sinkhole in the work zone.
Clearway would review the impacted area and proceed with machine rescue operations, including de-stressing and removing the steel tiebacks and undertaking jet and compaction grouting to stabilize the ground.
The budget for the operation would include improvement of ground conditions using phase compaction grouting.
The work was being undertaken as part of the City of Toronto’s Basement Flooding Protection Program.
WSP Canada has been advising the city on the rescue project.
Watch the DCN for updates.