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No matter how good system works, sewage will get in river
No matter how much money the city pours into a solution for sewage overflows, the problem will never truly go away, experts say.
The $260-million Ottawa River Action Plan (ORAP) will be funded by the city, feds and province, although the upper levels of government have yet to throw in their money.
Combined sewers, which mix storm water from heavy rainfalls with raw sewage, are what cause sewage overflows. The plan will split some of these combined sewers into separate pipes to drastically reduce the number of incidents.
While the 25-year plan is ambitious in scope, it will never put a stop to sewage overflows.
“As long as there are combined sewers, there’s always the danger that you get an extraordinary rain, and your system won’t be able to handle it,” says University of Ottawa water specialist Dr. Roberto Narbaitz.
“It’s going to be better, but if we had all the money in the world, we could make our pipes enormous so we wouldn’t have this problem. But as engineers and taxpayers, we want to only spend so much.”
Without what Narbaitz said would take billions of dollars, the city chooses to take that small amount of risk so it will only have a problem when there’s extreme rainfall.
Sensors that have been installed at five of the largest combined sewer outflows monitor water levels in real time and have already had a significant impact in reducing overflows.
Consider that in 2009, Ottawa had 384 overflow incidents that added up to 851 million litres seeping into the river from combined sewers.
That number dropped considerably in 2010 to 322 events and 673 million litres, and plummeted further last year with 161 events and 230 million litres.
While the numbers might seem astronomical, keep in mind the majority of the volume is simply rainwater, with raw sewage making up a small percentage of that.
Ottawa Riverkeeper Meredith Brown says the ability to monitor and control overflow valves greatly increases the city’s ability to manage combined sewers, and adding storage tanks will only add to that potential.
The city says in its ORAP report it will be able to reduce the number of events to virtually zero in an average year.
Brown argues it will likely be closer to five events per year, but that’s a huge improvement over hundreds of overflows.
“I don’t know of any city in North America that has none,” she says. “You have to be realistic and put it into perspective.”
But experts argue more can be done without upgrading costly infrastructure.
Since excessive stormwater is the real root cause of the problem, the city should offer tax benefits for tools that take water out of the sewers.
Investing in green roofs that absorb water, rain barrels and permeable pavement could have a huge impact, they say.