October 22, 2010
Toronto plans to spend $1 billion to clean waterways
With a number of stormwater management ponds and other facilities built and leading the way, the City of Toronto is looking to spend close to $1 billion to clean its waterways over the next quarter century.
The projects fall within the Wet Weather Flow Master Plan, a strategy designed in part to mitigate pollution that occurs when the city’s sewer system overflows during heavy rains, dispatching raw sewage into Lake Ontario and other waterways.
These overflows led the International Joint Commission, a Canada-U.S. organization that addresses water issues, to list Toronto’s waterfront as one of 43 areas of concern in the Great Lakes basin back in 1987.
Michael D’Andrea, the city’s director of water infrastructure management, says heavy rains sweep dog feces, oil from leaky cars and other contaminants into storm sewers. The rainwater then overtaxes the sewers, which in older downtown neighbourhoods are combined with sanitary sewers, and much of the mess ends up, untreated, in our waterways.
Factor in inadequate and aging infrastructure, and erosion caused by swiftly-moving stormwater runoff, and the need for action becomes apparent. “We have 2,600 storm sewer outfalls and about 80 combined sewer overflows, 31 of which flow directly into Lake Ontario,” D’Andrea says.
“We have several examples where sections of our sewers have been exposed, and in one extreme case we had a section of sewer that actually washed out. We also have basement flooding and sewage back-up issues.”
Approved in 2003, the Master Plan sets in play measures ranging from stabilizing stream banks to building stormwater ponds and storage tanks. Taking a watershed-based approach, the plan looks at the city as a whole ecosystem and breaks it into manageable pieces costing an average of $40 million over each of the next 25 years.
Not all projects mean construction work. One plank of the strategy is that rain should soak into the ground close to where it falls. So the city is phasing in a requirement to disconnect individual rooftop downspouts, and all new developments must meet stricter stormwater runoff controls.
However, the city has identified the need for 170 stormwater ponds and 43 underground holding tanks and tunnels to transport and treat runoff.
The plan presents challenges. There was room to build a large stormwater management facility at the mouth of the Humber River and a smaller pond to the east. But closer to the crowded downtown core, crews had to design underground systems such as the Western Beaches Storage Tunnel.
“That’s a large facility that intercepts (and treats) the stormwater and combined sewer overflows along that stretch,” D’Andrea says. “As we move even further into the eastern beaches, we’ve done the same thing with underground storage tanks.”
The city is currently in the middle of an environmental assessment for the substantial Don River and Central Waterfront Project that on its own will deal with some 50 combined sewer overflow and major storm sewer discharges.
“The plan right now calls for a very large network of underground storage tunnels both along the waterfront and lower Don River, some underground storage tanks, and a treatment facility to treat the flow we capture,” D’Andrea says.
Frank Zechner, water infrastructure advisor with the Ontario Construction Secretariat, says long-term planning means project planners can incorporate new ideas and technologies into successive rounds of work.
“That’s the right way to tackle it, doing it one step at a time. Identifying areas and small parcels makes it manageable and allows you to maintain some momentum.”
Zechner says the work is also good news for the construction industry. Every $1 million in capital cost translates into roughly five person-years of work for water infrastructure construction projects in the city. “That’s direct labour,” he says. “It wouldn’t account for engineering or supervision.”
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