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The Ottawa River may not be home to sticky and icky muddy waste just yet, but the city’s sewage system, like thousands of others around the world, still sends untreated sewage purposely cascading into the river several times a year.
Combined sewers, the aging infrastructure causing all the problems, are familiar to many city engineers.
Louis Julien, a water resources engineer at the City of Ottawa, says the capital is not alone.
“We’re one of thousands, if not tens of thousands of cities that have the problem.”
Any city built more than 50 years ago inherited the combined sewer system. In this system, the same sewer pipe collects all municipal sewage and storm water. When too much sewage floods the combined pipes, the extra load of effluent is dumped into nearby water bodies.
So in terms of the yuckiness factor, any water leaving a house qualifies as municipal sewage — including anything from the toilet — with the potential to end up in people’s favourite watering holes. Meanwhile, storm water includes anything that rain and melting snow pick up off the streets, like fertilizer and animal feces.
But the worry here isn’t about grossing people out. Scientists say the bigger concern involves people’s health and a polluted environment.
The major issue for the environment comes from suspended solids like clay or silt found in the sewage. These solids cause many negative environmental effects — from smothering fish habitats to interfering with photosynthesis in aquatic plants.
Beaches are often closed because of high levels of pathogens present in the water that put swimmers at risk for various diseases from the polluted water.
But Julien says the current sewer system in Ottawa shouldn’t keep residents up at night worrying about pollution or health problems.
“Anytime you have a combined sewer overflow, there’s a risk you have to face,” he says. “But to my knowledge we’ve never had any complaints or incidents related to [them].”
While sunbathers may protest that Ottawa beaches like Mooney’s Bay and Britannia Bay are sometimes closed in the summer after heavy rainfall, Julien says the combined sewers are not at fault because they aren’t anywhere near the beaches.
He says that in a given year, the total volume of overflows dumped into the river is only 400,000 cu. m, which may sound like a lot, but is really only a fraction of one per cent of the sewage that is treated.
“So it’s really a drop in the bucket, but that doesn’t mean we shouldn’t always be trying to reduce [the amount of overflows], which we are,” Julien says.
Even with the help of Environment Canada scientists though, it’s not easy to re-route the waste. There’s a high price tag to fix combined sewers, either through retrofitting present sewers or building completely new pipes.
Jiri Marsalek, a scientist at the National Water Research Institute, says they have been working with cities on how to fix combined sewers for more than 30 years.
“There’s no universal answer. All large Canadian cities have ongoing programs trying to fix this up,” he says. “We just have to keep in mind that it’s not cheap. Therefore the cities are proceeding at whatever pace they can perform.”
For the past few years, along with a team of experts — including ones from Environment Canada — Julien has been working on a plan to make better use of existing infrastructure to reduce the amount of sewage slipping into the river. It’s a plan he will present to Ottawa’s city council this spring.
Ottawa faces the same challenge of all other cities riddled with combined sewers. It’s a matter of money.
Julien says his solution would cost much less than Ottawa’s current plan to build an $80 million tunnel to hold the overflow.
While it may sound like a lot of money, fixing the problem could cost even more in large urban centres.
For a city like Toronto, Marsalek says it could cost billions of dollars to build new sewers. And that’s not even including the cost of disrupting important economic activities.
“Imagine that you’re in Toronto and you walk up to Yonge Street,” he says. “You shut it down for probably half a year and you start digging up the roads and sidewalks and you start installing additional sewers. That doesn’t look feasible.”
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