LICENCE TO DIVE
A TTC vehicle disappeared Tuesday into a massive sinkhole caused by a broken water main in the Port Lands, in what experts say is a warning sign of the city’s aging infrastructure. If you think this was a freak event, you may have another sink coming
A TTC worker managed to stay safe aand dry after escaping from his vehicle as it sank into a massive sinkhole in the Port Lands on Tuesday morning. The four-door sedan was not so lucky and was swallowed whole near Logan Ave. and Commissioners St. “We’ve sourced a rather large bag of rice to put the car in once it’s out so we can dry it out,” said TTC spokesperson Stuart Green with a laugh. The sinkhole — which the city said
was caused by a ruptured 300-millimetre, roughly 100-year-old cast-iron water main that created a void under the t road — is at least the seventh the Star has reported on this year. And it has experts sounding the alarm over the city’s aging underground infrastructure. The back end of the TTC car was just
visible, sticking out of a clear pool of water about six to eight feet deep, until crews removed it around 4 p.m. using cables and a backhoe.
The Wheel-Trans supervisor, who noticed flooding on the road while heading to the nearby depot early Tuesday morning, had returned in a TTC car to check it out, in case they needed to divert service. That’s when the road “opened up.” “He did try and manoeuvre the car out of what he assumed was a pothole, and when he realized that wasn’t hap-w pening, he got out, and water started to flood in. He got out quickly,” Green said.
It took a few hours for the vehicle to become completely submerged, Green added, with the car sinking quickly at first qand then “very slowly oover the course of the rest of the morn- ing.”
Sinkholes, basically holes in the ground, are “one of the most elusive problems engineers deal with,” says Mason Ghafghazi, assistant professor in civil engineering at the University of Toronto, adding they are mostly caused by water, typically by pipes bursting or extreme rainfall.
Water can wash away soil, creating a cavity that’s covered by an arch of pavement that then gives way under the weight of a car. “You can’t really predict them very well.”
In Toronto, they are mostly because of aging infrastructure and construction, he said.
In 2015, a stretch of road between 15 and 23 metres long around College and Yonge Sts. that dropped nearly 20 centimetres — called a “settlement” and not a sinkhole by the city — was blamed partially on a water main leak and vibrations from a neighbouring construction site.
“Infrastructure is getting really old, pipes that we have in the ground are sometimes a hundred years old, and so they’re getting to the end of their service life and they’re breaking more often,” Ghafghazi said.
Spring thaws can also mean an increased risk of naturally occurring sinkholes as frozen un- derground water starts to flow again, according to Steve Worthington, an expert on natural sinkholes from Dundas, Ont.
According to the city of Toronto’s website, water mains break more frequently in the winter because the soil freezes and expands. Corrosion can cause pits to develop in cast iron pipes, weakening them over time, and smaller cast iron water mains from the 1950s and ’60s are more likely to break because they have thinner walls.
The average Toronto water main is 59 years old, 13 per cent are between 80 and 100 years old, and 11 per cent are more than 100 years old. Water main pipes are typically buried about 1.8 metres deep (six feet) and about 1,400 water mains break every year in the city.
But it’s “unlikely” Torontonians would see “whole city blocks” or houses taken out by sinkholes, like has happened in other parts of the world, Ghafghazi said
“It’s not like we have a huge crisis coming our way.”
Asked about the specifics of the water main break, Bill Shea, director of distribution and collection for Toronto Water, said in an emailed statement it was likely caused by “corrosion or a pressure crack which is not uncommon in pipes of this age.”
The city budgeted $152 mil- lion to improve the water main distribution system in 2018 and replaces about 35 to 50 km of water mains each year, he added.
They can be a pricey problem. A 2015 Star story reported that in 2006, a 10-metre-wide sinkhole on Sheppard Ave. W. cost the city close to $1 million.
Now that the car is out, the city will be able to get a better look at the water main and estimate repair time. City staff will still need to pump out the sinkhole to remove the water, excavate around the infrastructure, backfill the site and repair the road, Shea added.
Urban designer Ken Greenberg, while not an expert on sinkholes, said it’s yet another sign the city needs to invest in its crumbling infrastructure.
“We’re growing at an astonishing rate and we’re clearly finding it difficult to keep up in terms of the basic infrastructure that supports the city,” he said.
“And so periodically we do have these breakdowns, which could be caused by any number of things.”
Sinkholes are different from potholes, which affect the surface level of the road.
Sinkholes can also be caused by chemical factors in the soil — water can dissolve some of the minerals inside soil and carry it away, said Ghafghazi.