Toronto Basement Flooding Areas 1&2

Project Details
  • Location
    City if Toronto
  • Project Contact
    • Christine Hill
  • Client
    City of Toronto
  • Completion


This project was developed and completed by XCG Consulting Ltd. or XCG Consultants Ltd. In April 2017, Cole Engineering Ltd acquired the projects, history and resources of XCG’s Water and Training & Operations business.

Project Highlights

Periodically, the City of Toronto (the City) has experienced both surface and basement flooding in response to relatively infrequent rainfall events. On August 19th, 2005, the City experienced a severe storm that resulted in the flooding of many residents’ homes, erosions in ravines and watercourses, and damage to City infrastructure such as roads, bridges, culverts and sewers. During this storm event, the City received over 4,200 reported basement flooding complaints, the majority of which occurred north of Highway 401. Subsequent severe flooding events occurred in 2012 in East York and in Etobicoke and the downtown core in 2013.  The City has identified 36 flooding areas ranging in size from approximately 20 ha to over 1,850 ha in size.
COLE has been retained to conduct Class Environmental Assessment studies to address basement flooding in Areas 1 and 2.  The approach to these basement flooding areas was different from previous basement flooding assignments completed by COLE because City staff prepared the Infoworks model for Areas 1 and 2.
This assignment involved extensive field investigations. Area 1 contained a number of dual manholes and COLE was able to confirm that flow could not pass between the storm and sanitary systems at the dual manholes. The field investigations also identified open style manhole covers on sanitary manholes which permit excessive inflow if there is any surface flooding or flow. The background information review also revealed floor drains were connected to the storm system instead of the sanitary systems. Area 2 investigations did reveal inconsistencies in the GIS data and actual field conditions which were used to update the model.
The InfoWorks models for both areas included sanitary, combined, and a dual drainage storm system. The modelling results were used in conjunction with historical records and public comment to identify the primary cause of basement and surface flooding. 
Multiple sanitary system and storm system alternatives were developed in Areas 1 and 2 and evaluated using a two-step evaluation process. The outcome was a preferred alternative consisting of sanitary sewer and storm sewer improvements sized to meet the City’s target level of service. The study also included conceptual design of all improvements.