06/06/2012 06:26 EDT | Updated 08/06/2012 05:12 EDT

Construction contributed to Union Station flood

The recent flooding incident at Union station resulted from a heavy rainstorm that overwhelmed a portion of a sewer that was undergoing maintenance.

The City of Toronto and the TTC have determined that intense rainfall last Friday caused “a rapid surge of storm water flow” through city sewers and wastewater treatment plants.

Ongoing construction at Union station has involved the reconstruction of a large sewer at the site, which is being completed by a TTC contractor.

At the time of the rainfall, a part of that sewer had been temporarily removed for construction reasons. Pumps were installed in its place.

Despite the presence of the pumps, “sanitary and storm water overflowed from the open section of sewer,” which is what caused the hours-long shutdown of Union station.

The TTC was forced to deploy more than 100 shuttle buses, as crews pumped the water out of Union Station, cleaned the facility and tested equipment.

Subway service resumed at 11:00 p.m., after being suspended on the Yonge-University line between Bloor and Osgoode stations since the early afternoon.

Additional pumps are being installed to prevent any similar recurrences as construction continues and the open section of sewer is due to be capped this Friday.