WC143 JulyAug 2025 - Magazine - Page 14
STORMWATER
silient and a more sustainable outcome,” particularly with respect
to some of the city’s more environmentally sensitive creeks.
Other key efforts Frigo cites include “moving away from dry
ponds to building ponds that work much more like natural wetlands” and through years of trial and error, “identifying different
species of plants that grow and thrive, slow down and filter water
and create biodiversity… which gives our communities a more
aesthetic function as well as better watershed outcomes.”
Despite those efforts, adding yet another layer of complexity to
his work is Calgary’s ambitious densification goal of increasing the
downtown population by 650,000 by 2069… which Frigo openly
admits could lead to “increases in hard, impermeable surfaces.”
In-between grey and green
The emerging trend of densification (as opposed to continued
urban sprawl) means that the heat islands effect will only get
worse, unless cities across the country get more creative when it
comes to how much hard surface is needed for roads, parking
lots, sidewalks and paths. And of equal importance, which types
of surfaces should be used to alleviate versus exacerbating the
occurrence of heat sinks.
When Ottawa-based PurePave Technologies was founded in
2012, the primary focus of the company, which produces permeable paving using a proprietary resin binder/aggregate/metals
solution, was residential driveways and sidewalks for homeowners concerned about potential basement flooding, runoff or both.
That focus has since expanded into working with cities such as
Toronto and Ottawa on pilot projects for high traffic areas where
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WATER C AN ADA • JULY/AUGUS T 2025
Going forward with green
Looking to the future, the way Toronto’s Hausmanis sees it,
“there’s a lot green infrastructure can do for stormwater management, but it has to be designed appropriately,” as opposed
to a less focused mindset of “let’s put in a bioswale here or
there hoping that it solves our problems. So we need to take a
strategic, consolidated approach.” And that includes, combining the use of existing solutions with new and emerging
solutions, such as permeable paving; which they are currently
assessing at sites such as the one in East York.
From Frigo’s perspective, there’s the need for “cross functional teams… so folks from our parks department, mobility
and transit departments all need to be involved,” to tackle the
city’s stormwater challenges. He says the city has developed
its own triple cost analysis tools to increase the likelihood that
whatever green infrastructure they do add to the mix is money
well spent.
Clearly, there’s the need for the private sector to step up as
well. As Davis puts it, apart from the exorbitant costs associated with solely depending on grey infrastructure, from a
practical standpoint, “you can’t just dig up the entire city and
replace and expand all of the stormwater infrastructure…
you’d be talking about shutting down cities for years and years
at the cost of billions.”
Which is why there very likely is a future in stormwater
management not just for grey, but also green and somewhere
in between.
WAT E R C A N A D A . N E T
Mark Wessel
Green Streets sites like this one at Lakeshore and Bonnycastle are designed to
help soak up heavy rainfall.
hard surfaces are required. For instance at one Green
Streets site in Toronto’s East York, the highly porous
PurePave system was installed as a boulevard instead
of concrete, enabling all of the surface water to flow
through to the trees, which five years after planting
are thriving.
Apart from working with cities to help solve their
stormwater headaches, PurePave CEO Taylor Davis
says a growing number of developers are already using and planning on using the permeable pavement
for their parking lots. By doing so, they are saving
money by either reducing traditional stormwater
systems or eliminating the need for them altogether.
One example Davis gives is a condo project in
Ottawa’s Carleton Place where “our engineers and
stormwater team punched the site’s metrics into
SpongeCity.ai to determine the optimal design for
the parking lot… which in this case, sloping the surrounding asphalt towards PurePaved parking stalls.”
A solution designed to absorb all of the precipitation
occurring on site so that none of the regular stormwater infrastructure was needed.
