Sewage leak in the Old Mill area could be related to removal of trapped boring machine

The City of Toronto is investigating a sewage leak in the Old Mill Drive area that could be related to a construction mishap beginning in the spring of last year.

In a statement provided to CTV News Toronto, the city said that there have been some “recent challenges” with the sanitary sewer system near Old Mill Drive and Bloor Street West which has in turn caused a back up that’s left residual materials and a smell in the area.

“City staff are actively investigating the cause of the odour and backup using CCTV cameras in the sanitary sewers in the area that run between Bloor Street West and Etienne Brule Park,” the statement notes. “City staff are also flushing and cleaning the sanitary sewer system – which regardless of the cause, will help to reduce the odour and risk of further backups. Depending on the findings of the investigation, further mitigation measures may be required.”

The investigation being launched by the city comes after the removal of a micro-tunnelling boring machine that was trapped underground in the area amid a construction project.

The machine was being used to build a storm sewer along Old Mill Drive, near Bloor Street West, in April 2022 to prevent basement flooding. The removal process, which was just completed last month, is expected to cost taxpayers more than $25 million.

While the city says that the flood prevention sewer and the sewage systems are not connected, previous efforts to remove the boring machine may have caused the blockage.

“It is possible but not confirmed that during the process of stabilizing the ground, some of the grout made its way into the sanitary sewer which, combined with other external material, is creating a blockage and causing the sanitary sewer to back up,” statement says.

The city says that clean-up efforts to remove residual materials in the area have already been undertaken