The Don River once got its own funeral, and today an Atlantic salmon has turned up near its new mouth.
In 1969, the group that became Pollution Probe staged a mock funeral for the Don, mourning a river that had been dredged, straightened and loaded with sewage and industrial waste. More than 50 years later, Toronto is finishing one of the biggest civil works projects in North America, carving a new river valley through the Port Lands and building a giant tunnel to keep sewage out of the water. So how dirty is the Don River, and is it really getting better? We dug into the facts.
HOW DIRTY WAS IT?
Very. In 1987, the International Joint Commission named Toronto’s waterfront one of 43 Areas of Concern in the Great Lakes Basin, largely because of poor water quality in the Don River and the Inner Harbour. The main culprits were combined sewer overflows, a mix of stormwater and raw sewage that spills into the river during heavy rain, along with polluted runoff from storm sewers. Nutrients in that runoff also feed the excessive algae growth that gives parts of the river its slimy look.
WHAT IS STILL POLLUTING THE DON?
Stormwater runoff remains the biggest contributor to poor water quality in the Toronto region, according to the Toronto and Region Conservation Authority. Winter brings another problem: road salt. TRCA reports that chloride levels at about 50 stream monitoring stations across the GTA almost doubled between 2002 and 2012, and that levels above 80 mg/L were already changing the mix of bugs living in local streams. Chloride doesn’t break down, so once it’s in the water, it stays.
IS IT GETTING BETTER?
Yes, and the work is massive. The City of Toronto calls its Don River and Central Waterfront program the largest water quality improvement project in its history: a 22 km system of three tunnels, 11 storage shafts and 27 connection points designed to capture combined sewer overflows and send them for treatment instead of into the river. The first piece, the 10.5 km Coxwell Bypass Tunnel, was completed in May 2026, with sewer connections to follow over the next several years. When the whole system is running, the City says overflows into the Lower Don will be virtually eliminated.
Above ground, Waterfront Toronto’s $1.4 billion Port Lands Flood Protection project gave the Don a new 1 km naturalized river valley. The concrete plugs holding back the water came out in July and November 2024, and the new river and Biidaasige Park opened to the public in 2025. Crews planted 5,000 trees, 77,000 shrubs and 2 million herbaceous plants to build new wetlands along the banks.
ARE THE SALMON REALLY BACK?
One is, and that’s a hopeful sign. TRCA crews found an Atlantic salmon in the lower Don for the first time since 2012, along with the first ever emerald bowfin upstream of Lake Shore Boulevard East. In 2024 alone, TRCA identified 29 fish species in the new river mouth, an area that had almost no fish before the project began. It’s a remarkable comeback for a river activists once held a funeral for.
WHERE TO SEE IT
Head to Biidaasige Park on Ookwemin Minising, Toronto’s newest island, where the new mouth of the Don meets Lake Ontario off Cherry Street. Walk north to Corktown Common, a park built on a flood protection landform, then follow the Lower Don Trail up the valley. Keep an eye on the water: you might spot some of those new fishy neighbours.
Have you walked the new Don River valley yet? Tell us what you spotted in the comments.