RC121 NovDec 2025 - Magazine - Page 28
FLOOD MITIGATION
way, you could divert water into the tunnel and send it directly to the
plant by gravity without pumping,” he says. “It also reduces 昀氀ooding
in some of the combined sewer storage areas… because some of the
surface 昀氀ooding can now be directed to the combined sewage storage
tunnel.”
In many respects, the massive size of the tunnel says Sandanayake,
was dictated by the fact that “we contemplated climate change (and)
we contemplated future development, growth and intensi昀椀cation.”
Notwithstanding the success of the CSST, to put matters into perspective he is quick to add that “one of the most e昀昀ective things we’ve
been doing since the 60s and we’re still doing, and we’re ahead of
schedule, is separating sewers.”
As a result, says Sandanayake “a lot of these small, combined sewer
outfalls no longer discharge any water. Why? Because we separated
all the sewers. Now there’s two sewers in the street. There’s a sanitary sewer and a storm sewer.” And every time a sewer comes up for
renewal it’s automatic that it will be separated. “We’ve already preplanned how to separate them,” he adds.
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Getting rain ready
Yet another highly successful initiative, as part of a suite of solutions
to address 昀氀ooding at the neighbourhood level, has been the Rain
Ready Ottawa program. The program was launched in 2021 as a pilot
project to encourage homeowners and businesses to do their part to
keep precipitation onsite (in contrast to the past priority of shunting
water away), with rebates of up to $5,000 per household tied to such
actions as the creation of rain gardens, downspout redirection and the
installation of permeable pavement.
To date, the program has supported more than 435 projects across
220 applications (with some homeowners tackling more than one
project) and according to Robinson, is on track for 2025 to be its most
successful year.
“The program demonstrates the power of seed funding to catalyze
action and investment,” observes Robinson. City rebates of $600,000
have leveraged $3 million in investment by private property owners in
onsite stormwater management.
More than 50 per cent of rebate applications include a permeable
pavement component and one of the most successful companies
involved in the installation of residential driveways has been Ottawa’s
own PurePave Technologies , which to date has done over 100 driveway installs.
With up front research partially funded by the National Research
Council, unlike conventional permeable paving, PurePave is made
from a proprietary mix of resins, plant-based polyols (contributing to
the surface’s 昀氀exibility, toughness, weather resistance and longevity),
metal powders, recycled materials and granite aggregates. Combined
with a 30-centimetre permeable base, the company’s site claims the
surface is capable of handling 38,000 litres of water per hour per
square meter.
According to PurePave CEO Taylor Davis, in the past, permeable
paving wasn’t all that e昀昀ective when it comes to rainwater retention
or structural performance. “Previously, permeable systems like brick
pavers weren’t giving the industry a very good name because with
only six per cent of the total surface area in昀椀ltrating water, that six per
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