Scarborough Waterfront Combined Sewer Overflows Outfall Control and Flood Protection Study

Recommended Infrastructure Improvements

Updated May 2021

The City of Toronto has a Study Addendum to update the 2011 Scarborough Waterfront CSO and Stormwater Outfalls Control Class Environmental Assessment (EA) and Flood Protection Study. The Study Addendum identifies solutions to reduce the risk of future flooding, address combined sewer overflow control and water quality. Following consultation with Indigenous Groups, Review Agencies, City Divisions and the public, the following highlights the main changes to the study recommendations:


    • More extensive sewer upgrades or realignment (total 28 km of primarily storm sewers)
    • Install up to 6 km of new storm sewers
    • Smaller underground combined sewage storage tank at the south end of Warden Avenue to store excessive storm and combined sewage during heavy rain periods
    • Eliminate several sewer system interconnections (between storm and combined sewer system)


To review the Executive Summary for Area 33 Study Addendum.

For more detail of the above Study Recommendations  Please call or email if you require assistance in reading this file.

Public Event November 26 2020 BF33 meeting notes Q A from the community.

Study Overview

The City of Toronto has initiated an Addendum to the Scarborough Waterfront CSO and Stormwater Outfalls Control Class Environmental Assessment (EA) and Flood Protection Study in early 2020. The EA was originally completed in late 2011 and an Environmental Study Report (ESR) was prepared. The ESR identified solutions to control combined sewer overflows and storm sewer loadings to Lake Ontario, and to mitigate surface and basement flooding during large storm events for areas along the Scarborough waterfront (See Study Area Map).

The objective of the Addendum is to review and update the findings of the 2010 EA and to issue an ESR Addendum. The Addendum will recommend solutions to reduce the risk of future flooding, address combined sewer overflow control and address water quality.

This project was recommended in the Wet Weather Flow Master Plan (WWFMP), adopted by the City in 2003 to provide an integrated work program for managing wet weather flow.

If you have trouble reading this map, please contact, 416,392-8210
Basement Flooding 33 Study Area Map

The study area is bound by Victoria Park in the west and Brimley Road in the east and sandwiched between the CN Rail in the north, and Lake Ontario shoreline in the south. This area is served by a mixture of combined, partially separated storm and sanitary sewers. There are six CSO outfalls which discharge into the lakefront at Fallingbrook Drive, Warden Avenue, Birchmount Road, Lakehurst Drive, Kennedy Road and the Scarborough Bluffs.

In the 1980s and 1990s, separate storm sewers were constructed in the majority of the study area thereby reducing the volume and frequency of the combined sewer overflows and eliminating basement flooding in many areas. Although much sewer separation has been done, combined flows are still large and hydraulic surcharging and basement flooding occurrences are avoided mainly by means of triggering many large overflows, or spillovers to the storm sewer system.

The Process

The Study Addendum is being planned as a Schedule C undertaking under the Municipal Class EA Process. The Study Addendum has identified the problem/opportunity, updated existing and future conditions, and evaluated the alternative solutions, recommended a preferred set of solutions, and identified measures to lessen any adverse impacts from the recommended solutions.


May 20 2021 Notice of Filing of Study Addendum

Public consultation is an important part of this study. A virtual Public Consultation Event was held on November 26, 2020 to present the updated alternative solutions and a preliminary preferred set of solutions for public comment.

The Study Addendum recommendations materials are available on the main page.


What is a Class Environmental Assessment?

Ontario’s Environmental Assessment (EA) program Opens in new window promotes good environmental planning by determining and managing the potential effects of a project prior to implementation.

Environmental Assessments identify and consider the potential impacts a project may have on a natural, social, economic, and technical environments.

If concerns regarding a project cannot be resolved in discussion with the City of Toronto, a person or party may request that the Minister of the Environment, Conservation and Parks (MECP) make an order for the project to comply with Part II of the Environment Assessment Act (referred to as a Part II Order), which addresses individual environmental assessments.

To submit a Part II Order request, refer to the MECP website Opens in new window for instructions.