Peeling back the Pavement - POLIS Water Sustainability Project

CASE STUDY 6
TORONTO’S MULTIDISCIPLINARY APPROACH TO
RAINWATER MANAGEMENT
The City of Toronto, Ontario is in the process of implementing a 25-year plan to help
solve water pollution in the city. Approved in 2003, the Wet Weather Flow Master Plan
(WWFMP) represents a comprehensive approach to urban stormwater governance,
with a focus on reducing pollution caused by stormwater runoff and combined sewer
overflows (CSOs).
In 1987, the International Joint Commission identified the City of Toronto waterfront as
one of 43 polluted Areas of Concern in the Great Lakes Basin. The geographic boundary
of the City of Toronto spans six different watersheds and from these watersheds pollution
from CSOs and stormwater runoff ultimately flows into Lake Ontario.
The WWFMP takes a hierarchical approach to rainwater management. It starts with
source controls, which deal with rainwater where it falls. It then focuses on conveyance
system measures and, finally, end-of-pipe facilities.
The plan identifies a host of measures to be implemented on individual lots including
using porous surfaces rather than concrete or asphalt, especially in parking lots; planting
trees to help capture runoff; a green roof incentive pilot program; and a rainwater harvesting
demonstration project at Exhibition Place, the city’s largest entertainment venue.
As the city’s aging sewer infrastructure requires replacement, it will be updated with
new purposefully “leaky” pipes that allow captured stormwater to seep into the
ground. What isn’t captured by the surrounding soil or sand will re-enter the storm
sewer pipes and will be controlled through end-of-pipe measures. In addition, a “search
and destroy cross-connections” program aims to fix linkages between drainage pipes
that are erroneously connected to sanitary sewers.
The total capital cost for the 25-year WWFMP is approximately $1 billion, or $42 million
per year. Operational and maintenance costs to implement the capital projects are
estimated at $16 million annually.
Complementing the WWFMP, the City has also developed the award-winning Toronto
Green Standard (TGS), which outlines performance measures and guidelines for sustainable
site and building design for new developments. It was developed collaboratively
across a number of divisions within the city, highlighting Toronto’s progress toward
integrating land- and water-use management and decision making.
Sources on page 67.
Photo (facing): hughreynoldsphotography.ca
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