TORONTO — Crews removed the first section of the micro-tunnelling boring machine (MTBM) used to construct a storm sewer along Old Mill Drive in Toronto last week.
The machine has been stuck underground since June 2022.
Full retrieval of the MTBM is anticipated take place in the next couple of weeks.
In April 2022, the $3 million machine was being used to construct a new 900-millimetre-diameter stormsewer along Old Mill Drive as part of the Basement Flooding Protection Program when it became entangled in steel tiebacks underground which were leftover from the building of a condo development.
In July, the Daily Commercial News reported that, due to complications, the cost to remove MTBM nearly tripled from $9 million to $25 million.
In 2022, the original cost estimate for the emergency work to retrieve the machine, which was based on the best estimate of the scope of work and costs at the time, was around $8.9 million. The extent of the emergency retrieval work became clearer in the spring and staff determined the cost may increase up to an additional $16 million.
The emergency retrieval process involved hand mining a tunnel from a shaft towards the MTBM.
During the hand mining, groundwater was encountered and entered the tunnel. In order to safely proceed with the removal of the machine, the water needed to be removed and the surrounding ground area stabilized.
Clearway Construction Incorporate is the contractor removing the machine. After the removal, the city will complete the installation of the new 900-millimetre stormsewer to help protect the area from basement flooding.