WC143 JulyAug 2025 - Magazine - Page 22
As of March 2025, the Coxwell Bypass Tunnel (stage one) is
approximately 99 per cent complete.
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WATER C AN ADA • JULY/AUGUS T 2025
to build the Coxwell Bypass. The 115-metre-long machine
weighed nearly 1,000 tonnes and was lowered in sections into a
50-metre-deep, 20-metre-diameter shaft at Ashbridges Bay and
then assembled. “It was able to bore at least 20 metres of tunnel
per day,” Di Gironimo says.
Still, the prize went to the machine digging the nowcompleted outfall from Ashbridges Bay out into Lake Ontario.
Work started in 2020, when COVID lockdowns and travel
restrictions were in place, so the machine’s commissioning
team worked remotely with mobile cameras and radio repeaters
to conduct a factory acceptance test to officially declare the
machine safe to begin its trek beneath the lake bottom. “It
went three and a half kilometres, did a hard dive down, and
buried itself.” Di Gironimo says, explaining that tunnel boring
machines of this sort can’t back up. “When you’re doing an
outfall under water there’s no way to retrieve it. So we’ve
entombed and sealed it in a waterproof concrete liner, and
it’s never coming out.” The Tunnelling Association of Canada
awarded the outfall Canadian Project of the Year (over $100
million) in 2023.
While large wastewater projects are common enough, what
makes the Don River and Central Waterfront Wet Weather
Flow System program stand out is the bigger picture of
interconnectivity between the new treatment and management
systems. “A lot of them are designed to just collect, store and
release stormwater afterwards for treatment,” Di Gironimo
says. “But that’s just the bare minimum that we wanted to do.
This is an integrated, end-to-end approach that gives us greater
flexibility on how to manage flows in the future.”
In its entirety, the Don River and Central Waterfront Wet
Weather Flow System program will add more than 650,000
cubic metres of overflow storage. Di Gironimo does caution that
the program won’t spell an absolute end to overflows because
even stronger storms could potentially have unpredictable
impacts, but it does stand to go a long way towards improving
the environment and city life for many years to come. Dianne
Saxe, a Toronto councillor who sits on the city’s infrastructure
and environment committee, concurs. “It’s a hugely expensive
project, it will take many years, but it’s really important for the
quality of the water in our lake and along our waterfront.”
Saxe recalls spending much of her childhood in and around
Toronto’s beaches. “My mother learned to swim in Lake
Ontario, at Sunnyside Beach. It used to be clean and safe, and
then we had decades of it being really dangerous, gummy and
covered in algae. Climate change is increasing the intensity of
rainfalls, urban sprawl is increasing the speed of runoff, and
we’re adding hundreds of thousands of people to the city, so the
problem will worsen rapidly unless we get ahead of it. Having
a clean waterfront that we can enjoy will add so much to the
quality of life in the city and to human health.”
Black and Veatch
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