Mostly I'm posting this because Wikipedia has an entire category of photos called "Dredges In Toronto" which I happened to stumble upon. Dredges are the crane-like things people use to dig up the bottoms of bodies of water. Wikipedia has 15 photos of them in Toronto and this is the oldest: from the 1890s. Up until that point, the land that's now the Port Lands at the mouth of the Don River was a big marsh. I'll write a full post about it someday — the Ashbridge's Marsh was the biggest wetland on the Great Lakes and plays a pretty interesting role in the history of Toronto — but for now I'll just mention that by the end of the 1800s, it was polluted as fuck. The nearby Gooderham & Worts Distillery flooded it with waste — including as much as 80,000 gallons of liquid manure a day. The City tried to ignore the problem for years, but eventually the threat of cholera and looming court cases forced them into action. One of the ways they tried to deal with it was by creating the Keating Channel, re-directing the Don into the harbour to the west and Ashbridge's Bay to the east so that the waste would be dispersed more quickly. That's what they're doing with the dredge in this photo: making "the Keating cut".
Eventually, the City decided to fill the marsh in entirely — and with it most of Ashbridge's Bay. Today, the Keating Channel is still there, regularly dredged by the Toronto and Region Conservation Authority to keep it clear. It's far from picturesque, though, and not exactly an ideal habit for wildlife — the sides are lined with concrete. The new plans for the development of the Port Lands will renaturalize the mouth of the river and keep the Channel. The idea is to build a "sustainable mixed-use neighbourhood" around it, so that it "will be dramatically transform[ed] into an upbeat, unique canal destination. It will be lined with public space and traversed by a series of four new bridges for vehicles, transit, cyclists, and pedestrians... It will feature parks and promenades along its edge, water access for boats, plus it will have amenities such as shops and canal-side cafés."