Toronto’s natural drainage systems, its ravines, get a makeover

The City of Toronto is spending billions to help the Don River and its tributary, Taylor-Massey Creek, recover from age-old scourges such as combined sewer overflows. Can they be resurrected after centuries of abuse?

Theglobeandmail.com
April 26, 2021
Matthew McClearn

Promotional videos cast Toronto’s ravines as “natural expressways,” ecological wonders in which residents connect with wondrous biodiversity. Their green canopies cut through neighbourhoods and commercial areas alike, and their streams sparkle between the city’s ribbons of blacktop. But attentive visitors to the lower reaches of the Don River and its tributary, Taylor-Massey Creek, might notice some decidedly unnatural features. Their banks are lined with rock-filled gabion boxes, armour rock and corrugated metal, portions of which toppled over long ago. Ravine slopes are strewn with trash. And every few hundred metres the banks are interrupted by pipes and outfalls, which attest to the river’s unspoken but primary function: open sewer.

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However degraded the Don River watershed may seem today, it has seen worse. But now the municipality is undertaking a $3-billion project it calls the “largest and most significant water quality improvement program in the city’s history” -- indeed, in the entire country. It’s building the first of three tunnels that will stretch 22 kilometres across the city, diverting untreated sewage away from the ravines to the sprawling Ashbridges Bay Treatment Plant for processing.

A multi-billion-dollar makeover for Canada’s most urbanized watershed

It’s timely because, at the Don’s mouth, the decrepit Port Lands industrial area is in the midst of its own multibillion-dollar makeover. The river will be redirected and “renaturalized,” part of a radical redevelopment that includes building a new neighbourhood called Quayside and a marine recreational area called the Parliament Slip, as well as redeveloping the Port Lands into a mixture of commercial and residential areas lined with parks.

Excrement floating by -- that simply wouldn’t do. Nor would watching all of it get washed away by catastrophic floods. Toronto is bent on eliminating both hazards. But as with a pop star after a fifth round of plastic surgery, the question is no longer whether the Don can be restored to anything resembling a natural state; the question, rather, is the same that has attended every “improvement” project for the watershed over the past century and more: Will the next intervention actually make things better?

This time, the answer seems to be, well, probably yes. And it’s indicative of how people can partly restore ecosystems they have abused for centuries -- as well as a reminder of how costly and time-consuming such restoration can be.

To outsiders, Torontonians’ preoccupation with the Don River may seem perplexing. It is a mere trickle compared with the Mackenzie, Fraser or St. Lawrence rivers. Even at its lowest reaches it is barely a metre deep and therefore not navigable in anything larger than a canoe. Nor is it broad -- a child can throw a stone across it.

Originating from a stormwater outfall just south of Highway 401, Taylor-Massey Creek is even less impressive. It meanders through the Scarborough and East York areas of the city, gurgling pleasantly through ravine parks such as Warden Woods and Taylor Creek Park. When blooming foliage conceals the trash-strewn ravine slopes and a creek bed littered with concrete rubble and other erosion control material, these parks seem idyllic; elsewhere, the creek seems little more than a drainage ditch.

After more than two centuries of unrelenting abuse, the Don and its tributaries do possess one notable distinction: York University history professor Jennifer Bonnell called them “the most urbanized watershed in Canada.” Almost all of its wetlands were filled in or drained long ago. The Lower Don was straightened to accommodate railways in the late 19th century, and for 60 years valley visitors have been serenaded by the cacophony of bumper-to-bumper traffic from the Don Valley Parkway.

It bears repeating: The Don and Taylor-Massey Creek have seen worse. Sewers were run through the ravines during the late 1800s. Prof. Bonnell’s 2014 book, Reclaiming the Don: An Environmental History of Toronto’s Don River Valley, recounts that by the 1880s the Lower Don was regarded with utter contempt: “It was a place to be avoided, denigrated, cast from the mind, and with it, the sewage, the offal, and the effluents; the impoverished, the homeless, and the insane.” Its defilement peaked in the late 1950s, when rapid urbanization conspired with inadequate sewer infrastructure to produce an olfactory abomination that beat back all but the most determined intruders.

Today it’s cleaner than it’s been in almost a century, thanks to numerous though typically small initiatives. “There’s been a lot of pressure by citizens groups to change the thinking that the city’s ravines and waterways exist for the movement of sewage,” Prof. Bonnell said in an interview. “To even be able to imagine a future where we might have clean water in the city’s creek beds, that’s a big shift.”

The municipality has installed storage tanks for wastewater, for example, and ordered homeowners to disconnect their eavestroughs from storm sewers. The city’s street sweeping program reduces particulate matter and other contaminants that would otherwise end up in stormwater drains. A philosophy underpins all this: Stormwater should be dealt with close to where it falls rather than evacuating it wholesale through sewers, creeks and rivers.

The Toronto and Region Conservation Authority (TRCA) has data on key contaminants from 1979. Angela Wallace, the senior project manager for aquatic monitoring and management, said it shows gradual improvements in dissolved oxygen, phosphates and suspended solids on the Lower Don. “It is improving, for sure,” she said. (Water quality along Taylor-Massey Creek, on the other hand, remains largely unchanged.)

Yet even as the city spends billions fixing yesterday’s mistakes, more people are moving into the city and land is being developed with greater intensity. A warming climate is expected to produce more sudden downpours, which send deluges cascading through Taylor-Massey Creek and the Don, cutting deeply into banks and splintering wood bridges.

Of yesterday’s mistakes, however, few have proved more daunting than combined sewer overflows.

Combined sewers (in which both sanitary sewage and stormwater share the same pipe) still serve Toronto’s oldest neighbourhoods, accounting for roughly a quarter of the city’s sewage system. Normally, the foul contents are handled at sewage treatment plants; however, during heavy rains, they can be discharged directly into the city’s rivers and creeks. (Municipal reports show outlets have released untreated sewage even during dry weather.)

Nobody knows how much sewage flows through Taylor-Massey Creek and the Don. Clearly, however, they remain veritable conduits for fecal contamination. In 2019, the TRCA’s annual report on water quality found that E. coli counts at its monitoring stations in the Don were consistently above provincial standards.

The three new tunnels will effectively replumb older neighbourhoods, directing their sanitary sewage to the Ashbridges Bay Treatment Plant. Since construction began in 2018, a tunnel boring machine has excavated roughly half the 10.4-kilometre Coxwell Bypass tunnel, roughly 50 metres underground. Four of five large storage shafts, which will store stormwater during extreme rainfall until it can be treated properly, have also been cut. When all three tunnels are completed around 2038, combined sewer overflows would cease forever.

“Rerouting the CSOs is a big deal,” Ms. Wallace said. “Once they take all of those offline, there should be some sort of recovery” in the watershed.

That’s good news -- not only for the ravines, but also for the Port Lands.

After passing under a crumbling elevated expressway, the Don takes a hard right turn into Keating Channel, flowing past the derelict buildings of the Port Lands into Toronto Harbour. Built on the filled-in carcass of obliterated wetlands, the Port Lands are roughly the same size as the downtown core, which is just 20 minutes away by bicycle. Yet until recently the area has resisted redevelopment, for two reasons: Its soils are thoroughly contaminated, and the whole area lies within the Don’s floodplain.

So the city and its partners (including Waterfront Toronto, a body formed by several layers of government to revitalize Toronto’s blighted waterfront lands) are cutting a new channel, following a route closer to the river’s original course. Rather than hemming its banks in with steel and concrete, this channel will be lined with a “green spillway” that will allow the Don to spill over its banks. Keating Channel will remain as a sort of relief valve, and water will also be able to spill over into the nearby Shipping Channel during the worst deluges.

David Kusturin, Waterfront Toronto’s chief project officer, said the new channel is already half-excavated. Now that the central river valley has been cut, workers are placing aggregate stone at its bottom and building levees for wetlands. “We’ll be putting in wood cribs and stone to really armour up and support the sides and the banks of the river so that when we have major floods there’s minimal damage to the river itself,” he said. The river will be opened to its new course just a few months before the overall completion of the Port Lands project in March, 2024.

Ms. Wallace said the two projects should significantly improve water quality along Taylor-Massey Creek and the Lower Don. This should provide much-improved habitat for fish species such as Chinook salmon and walleye.

“It’s still going to be a very urban watershed,” she said. “But urban systems can still be healthier than what the Don is now.”