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The following is provided as background information and shows the development of the Wet Weather Flow Management Master Plan.
What is a CSO?
A CSO is "wet weather
lingo" for "combined sewer overflows". Toronto's original sewer
system was a combined sewer system: it was "combined" because the
storm drains and sanitary drains flowed into a single system of
pipes that discharged directly to rivers or the lake. Overflow points
- combined sewer overflows -- were added along the system to protect
it from damage caused by excessive flows. In modern sewer systems,
storm systems are separate from sanitary sewers.
Combined sewers are still found in some of the old parts of Toronto,
including much of the former municipalities of Toronto, York and
East York and the southwestern part of Scarborough. When it rains
in these areas, dilute sewage mixed with stormwater is discharged
into rivers and the waterfront through the 71 CSOs that remain.
It is a priority for the City to address the pollution caused by
CSOs, as they are a significant source of pollution including bacteria,
nutrients, metals and organic compounds.
What kind of options for dealing with wet weather flow will
be considered in the Master Plan?
The City will considering all options, from disconnecting downspouts
to cleaning catchbasins to building stormwater ponds, soak-away
pits and wetlands. By January 2001, we will have a report on the
options ready. It will include information on such factors as cost,
effectiveness and ease of implementation. The document will provide
a base for Phase 2 activities. This will include an analysis of
what opportunities to implement the options exist in each of the
5 study areas.
Are some options for dealing with wet weather flow better than
others?
Yes, in the sense that it is always better to prevent pollution
rather than to treat it at the end-of-pipe. That is why the City
is using a hierarchical approach to evaluating options.
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At Source:
First, examine how to deal with stormwater where it falls. |
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Conveyance:
Next, deal with stormwater and combined sewage as it is being
transported across the city. |
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End-of-Pipe:
Finally, deal with stormwater and combined sewage before it
is discharged into our streams, rivers and Lake Ontario. |
This new philosophy was a result of multi-stakeholder involvement
early in the Master Plan process.
Why do we have to develop a Master Plan? Why can't we just fix
the problem?
In a sense, we have been working on fixing the problems of wet weather
flow for many years on a piecemeal basis, through the programs carried
out by the City of Toronto, its former municipalities, the Toronto
and Region Conservation Authority, and other initiatives including
the Toronto and Region Remedial Action Plan. The Wet Weather Flow
Management Master Plan provides the opportunity for us to address
the problems in a holistic manner - to involve all stakeholders,
to look at all the problems, and to devise the best strategy to
address them. The Master Plan will allow us to look at a complete
range of options and select the ones that are most likely to lead
to healthy rivers and a healthy waterfront.
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