A corroded 24 inch water main running beneath Sheppard Avenue West burst open late Tuesday night, weakening the road's foundation and causing it to sink about three metres.

When the pipe burst, water gushed to the surface and forged a destructive path.

It was a dramatic moment as the water broke through the surface, according to a man who was underneath a bridge on Sheppard Avenue West.

"All I heard was a little bit of rocks move and a great big thump, like the whole bridge moved," the man told CTV's Austin Delaney. "And then all the gravel and everything started pouring down both sides of the bridge."

All four lanes of the heavily-travelled Sheppard Avenue West between Bathurst and Senlac were closed on Wednesday. Plus, water service to a nearby apartment building was cut off, prompting city officials to deliver portable toilets and bottled water to the residents.

Toronto's general manager responsible for water services said the city experiences approximately 1,500 water main breaks every year and it is difficult to predict where and when the next one will happen.

"If you use an analogy from the health sector, it's like having cancer," Lou Di Gironimo said. "You know it's in the body but you have to find where it is."

But Toronto's infrastructure is getting older and city hall is spending nine per cent more this year to keep it in working order.

"We can't go on deferring aged infrastructure repair and there is a very strong commitment to that in the water budget," Works Committee Chair Shelley Carroll said.

She said if the city does not do the work, there will be more incidents like the one on Sheppard Avenue.

The city is feeling some urgency to keep the pipes in good repair. Sheppard Avenue's water main was over 50-years-old and 7 per cent of the city's underground water pipes are over 100-years-old.

With files from CTV's Austin Delaney and The Canadian Press