Fill out our survey to help the City determine the source of basement flooding in your community.
Survey closes December 31, 2022.

During heavy rain, sewers can become overloaded. This increase puts pressure on the sewer systems and overland drainage routes, such as roads, local rivers and streams, which can lead to basement flooding.

In 2013, City Council approved plans to develop comprehensive plans in 67 areas across the City to reduce the risk of flooding. The study areas were determined by the underground drainage system.

For each basement flooding area, a Class Environmental Assessment (EA) study is conducted (see below for more details). These are complex studies that can take two or more years to complete.


In fall 2019, the City of Toronto initiated Basement Flooding Capacity Assessment engineering studies for the last 21 of the 67 study areas. The studies are to determine the cause of basement and road surface flooding and propose sewer improvements to reduce the risk of future flooding. This is part of the citywide sewer infrastructure improvement capital program. This new, accelerated process is to develop sewer improvement plans within the City’s right-of-way (roads). Potential drainage improvements identified through these studies can include sewer upsizing, in-line underground storage and modifications to catch basin capacity.


To assist the City in determining the source of the road surface and basement flooding, please fill out a five-minute online survey. Your participation in this survey is voluntary and greatly appreciated. Information collected will solely be used for sewer planning purposes.


For areas where more complex infrastructure may be required outside of the City’s right-of-way, an Environmental Assessment (EA) study is conducted. These are complex studies that can take two or more years to complete.


Class EA studies:

  • assess the sewer and drainage system capacity
  • make recommendations to reduce the risk of flooding

Your home or property may be located in other study areas where EAs have been completed or planned for current drainage capacity assessment.

Basement Flooding Study Areas

Find out about active and completed study areas and the study area you live in.

Scope of the Study

See what's covered and not covered by the study and also answers to common questions.

Steps in the Study Process

Learn about the typical steps in the study process.

What is a Class Environmental Assessment?


The process of estimating and evaluating significant short-term and long-term effects of a program or project on the quality of its location’s environment. It also includes identifying ways to minimize, mitigate, or eliminate these effects and/or compensate for their impact.

The Environmental Assessment sets out a planning and decision-making process so that potential environmental effects are considered before a project begins.

Environmental assessment can be defined as identifying, estimating, and evaluating the environmental impacts of existing and proposed projects, by conducting environmental studies, to mitigate the relevant negative effects prior to making decisions and commitments.

The Municipal Class EA applies to municipal infrastructure projects including roads, water and wastewater projects. Since projects undertaken by municipalities can vary in their environmental impact, such projects are classified in this Class EA in terms of schedules:

Schedule A/A+
• Generally includes normal or emergency operational and maintenance activities
• These projects are pre-approved, however the public is to be advised prior to project implementation

Schedule B
• Generally includes improvements and minor expansions to existing facilities
• There is the potential for some adverse environmental impacts and therefore the proponent is required to proceed through a screening process including consultation with those who may be affected

Schedule C
• Generally includes the construction of new facilities and major expansions to existing facilities
• These projects proceed through the environmental assessment planning process outlined in the Class EA

Master Plans

Master Plans are long range plans which integrate infrastructure requirements for existing and future land use with environmental assessment planning principles. These plans examine an infrastructure system(s) or group of related projects in order to outline a framework for planning for subsequent projects and/or developments.

This overall planning approach recognizes that there are real benefits to the process when comprehensive plans are undertaken for projects which have some common elements such as geography or function. Master planning provides the municipality with a broad framework through which the need and justification for specific projects can be established and the environmental assessment process can be satisfied.