Driftwood and garbage gathers at the sharp turn where the Don River turns west into the Keating Channel

Scraping the bottom of the channel

PortsToronto prevents flooding by dredging the Keating Channel with ailing equipment that may not see tomorrow

Every summer, PortsToronto spends 12 weeks dredging — digging up slime and muck from the bottom of the Keating Channel — where the Don River takes a 90-degree turn before spilling out into Lake Ontario.

“Once we pulled out two vehicles up by the pub. One was a Porsche, the other I think was a Ford Taurus.”

—Don Murphy

Over the year, sediment, garbage, and driftwood gather in the Keating Channel, making it shallow, and creating flood risks for the lower Don Valley.

The sediment gathers all along the channel, but the worst build-up happens at the bend, near Lake Shore Boulevard and the Don Roadway.

“One year the sediment was up so high, birds were able to sit on the sand,” remembers Don Murphy, the hoisting engineer. Murphy runs the dredge machine, and is responsible for moving the scows.

Along with the sediment, booms catch large swaths of garbage and driftwood carried down the Don River. In 2014, 880 tonnes of driftwood were pulled from the channel.

“After a good rain fall, we’ll fill at least five big green bins with stuff the booms catch,” Murphy said. Often they fill 12 of these 40 cubic yard bins. And the booms still don’t catch it all; often the rushing water will push stuff over the booms, carrying it further down the channel.

What happens to the full storage cells?

The storage cells, called confined disposal facilities, are capped when filled, to isolate disposed materials. The first cell was capped in 1985, and has since been restored as wetland. Cell One was completed in 2005.

Cell Two will eventually be turned into a 9.3 hectare coastal hemi-marsh ecosystem. Fish and wildlife habitats will be restored to the cell. The project will wrap up in 2017.

Source: tommythompsonpark.ca

The sediment takes a little more work.

“We use the Derrick 50, a floating crane with a clamshell bucket,” Murphy explained.

“We remove the sediment and put it in dump scows and port it out to the Leslie Spit and get rid of it.”

The annual goal is 40,000 cubic metres of sludge (about four scows a day for 12 weeks) lifted out of the channel and moved to the Leslie Spit. The sediment is deposited in one of three cells in the Leslie Spit. Filled cells become a base for Toronto and Region Conservation Authority wetland rehabilitation projects.

 

Key areas in the PortsToronto dredging operation that sees tens of thousands of cubic metres of sediment removed from the Keating Channel every year.

However, equipment failures have plagued the operation.

The Keating Channel bridge broke down in 2010, preventing dredging operations for the year. PortsToronto has been playing catch-up ever since.

“Our goal has been 150 per cent of what we had before,” says Mike Lamont, manager of the Works Department. “It’s 60,000 cubic metres now, but they haven’t quite gotten there.”

Aging equipment and a broken tug have slowed the process, and increased the price tag. The William Rest tugboat has been on the fritz. To continue dredging, PortsToronto had to contract out another tugboat. Come June, the contracting will end when the new Iron Guppy tug arrives, with a $3 million price tag, to replace the ailing William Rest.

Along with the new tug, PortsToronto will be preparing their new spud barge with a long reach excavator perched upon it to replace the derrick.

Not everyone thinks the new acquisition is for the best.

“It was only a test run, but when we used the spud barge and excavator last year, it took us two hours to do what the derrick did in 45 minutes,” said Murphy.

“Ultimately, we want a crawler crane,” said Lamont, looking at a photo of the Liebherr LR 1300 on the wall. “We just don’t have the money for it.” However, Lamont is searching for a good used one.

Come summer, the dredging must begin again, crane or not. As always, PortsToronto will do their best with what they have, and keep the Don River from overflowing its banks.