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Toronto moves to rescue ensnared boring machine

Don Wall
Toronto moves to rescue ensnared boring machine
CITY OF TORONTO—A City of Toronto report depicts a micro-tunnelling boring machine entangled in a steel tieback in a tunnel on Old Mill Drive.

TORONTO—The City of Toronto has hired 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 that was awarded to Clearway was $9 million.

According to the 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.

Completion of the remaining section of the recovery tunnel along with removal of the micro-tunnelling boring machine is anticipated to require two to four weeks with completion targeted by the end of March 2023 or early April.  The budget for the operation includes 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.

This story had been revised from an earlier version to reflect the proper contract timeline.

Watch the DCN for updates.

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