When the city becomes a water world
Are our older sewers affecting our ability to cope with flooding?
It’s not directly related to their age. Our existing sanitary and stormwater systems were based on design guidelines that handled storm events in a two- to five-year frequency, the typical design standard used by many municipalities.
How do sewers that are over 100 years old stand up to extreme weather events?
In the older downtown core, you will find some sewers from the late 1800s and early 1900s that are brick-lined. We have to deal with fixing those as they decay, but they’re not as bad as you’d think.
[But] some of the 1920s, 30s, 40s vintage – the older areas needed some retrofit work in order to deal with the new treatment technologies.
Can those pipes handle what’s being thrown at them with extreme weather like last July’s torrential rain?
In the downtown core we have one pipe for domestic sewage flow and one for rainwater that flow into a combined sewer. That’s why when we have flooding or an extreme storm event you don’t hear about older buildings in the downtown area flooding. The water gets into the environment it doesn’t get into basements. Where we’ve been having difficulty with these extreme storm events is in the rest of the city, where we do have separated systems. So the rest of the city was built with two pipes in the ground, one that deals with the sanitary flow and one that just deals with stormwater flows. The stormwater flows don’t go to a sewage treatment plant they go to your local ravines and creeks. What we are doing is channelling that water out into the environment, and we’re allowing it to flow out to where it normally did before into our creeks and rivers.
Right, so then why do we have massive overflows happening?
The designers of the system didn’t contemplate these types of storms. We didn’t have any record of these types of storms. These events are starting to break records.
The analogy I give councillors is that we designed a bathtub. There’s an overflow safety valve – that’s the round rig you see in the bathtub. If you leave the tap running, the water won’t overflow because it’ll spill into that overflow valve and go down the drain, and it protects your house.
Well, that works if the overflow is at the rate of your faucet, because it’s designed for that. [But] what if you filled your bathtub with a firehose? Guess what? You’re going to overflow. That’s essentially what happens when we get an extreme storm. You’re dumping so much water so quickly, you completely overwhelm not only our systems, but also Mother Nature herself, because the ravines fill up very quickly.
How is our 10-year plan shaping up to handle this new reality?
I’d say we have a good plan in place. We have a lot more work to do – don’t get me wrong. We’ve got the plans and the funding mechanisms in place now it’s a matter of executing the plans and staying the course. That’s what sustainability’s about. It’s a long-term commitment.
Is our infrastructure plan difficult to sell because it’s hard to make water, wastewater, sewage and poop sexy?
Again, I would say no. There’s only so much work we can do in a year without physically shutting down.
One thing to look at is affordability. The second thing is how much work we can get done and how we sequence it. How do we coordinate it with other things going on in the city – with transportation projects, the Pan Am Games, Union Station revitalization?
There’s only so much money we can actually spend in a year. I know I need another $1.5 billion worth of projects after that, so those sets of projects are already looking out a 25-year window, if not a 30-year window.
The question is, are we fully sustainable? No, we’re not probably fully sustainable yet with everything we have to do, but we’re on the right track. We’ve made big strides. And we have the opportunity to keep tweaking our program toward greater sustainability.
firstname.lastname@example.org | @cynthiajmcqueen