TORONTO – On the morning of June 1, a brief, but intense rainfall event caused a rapid surge of storm water flow within the City’s sewer collection system and wastewater treatment plants. (The downtown area experienced rainfall ranging from 27mm to 37mm.) The heavy rainfall event did not exceed the capacity of the entire sewer collection system.
The City of Toronto and the Toronto Transit Commission are launching an investigation to uncover what happened.
As part of the contract for the TTC’s Union Station New Platform Project in the subway, the TTC’s contractor is also reconstructing a large sewer on behalf of the City for the Union Station Revitalization Project. To enable construction of the new lowered sewer, a section of the existing sewer was removed and pumps put in place in order to install maintenance holes at one of the future connection points. During the heavy rainstorm, sanitary and storm water overflowed from the open section of sewer at this location (flooding was localized to this area of the City).
The contractor and the project management team are working to put in place measures to avoid a recurrence during construction. One such measure includes the installation of two additional pumps on site as contingency. As well, the pipe that was temporarily exposed to perform this work will be capped by Friday.
Subway service on the Yonge-University line was suspended between Bloor and Osgoode stations at about 12:30 p.m. Friday. TTC crews pumped out the water from track level, cleaned the station, and tested safety critical components of the subway before service was able to resume at 11 p.m. During the service interruption, up to 118 shuttle buses were deployed along Yonge St. to bridge subway service.