Cavern construction: Sand, cement fill Allendale Road underground cavity

Construction work continues to repair the cavern — likely created by a broken water pipe — discovered underneath Allendale Road last year.

The underground cavity, found in August during an inspection of a manhole near Allendale Road and Calgary Trail, measures seven metres wide, with an estimated size of 700 cubic metres.

“We believe that there was an underground pipe failure that occurred which created a pathway for water, which eventually would have eroded the ground around the failure and created the void,” said Kelly Struski, spokeswoman for Epcor, the city-owned utility.

“But we’re not able to make a final definitive determination on what that cause would have been.”

In order to repair the cavity, a new manhole is being constructed and the void itself is being filled with a sand and cement mixture that is self-compacting. It hardens quickly and because of its load-bearing properties, it is able to stabilize the road.

Struski said there’s no particular area of the city that would be prone to similar underground holes forming.

“We regularly inspect and rehabilitate drainage infrastructures. Localized failures can occur for various reasons and once damaged, there can be rapid deterioration in some cases,” said Stuski.

“Our inspections are completed with remote cameras inside of the pipe. Localized issues that might have occurred outside of the pipe may not be possible to detect.”

Repair work on the road is expected to be complete by mid-February, with the road restored and lanes reopened.

But other maintenance work is required on the 1.2 metre-diameter drainage trunk line, which would require lanes to close down again for about two to three weeks.

Epcor is anticipating that work won’t begin until the spring. However, Struski said that timeline is not set in stone.

ajunker@postmedia.com

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