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Sinkholes generally caused by underground water, Calgary transportation official says

A sinkhole on a busy Calgary road that affected Friday rush hour traffic is likely caused by flowing underground water, a transportation official said.

It opened up between 26th Avenue and 33rd Avenue S.W. on southbound Crowchild Trail Thursday evening.

Sean Somers of the transportation department says rain may have been a contributing factor but is likely just a coincidence. He says usually it is a leaky pipe that is to blame, but in the case of Crowchild Trail it's likely underground water.

"We have different layers of compacted material, typically sand, gravel, rock and so on and then the final lift of pavement on top. Water washes away all that underfill, there is nothing to support the pavement and it collapses," Somers said.

He said the Crowchild Trail sinkhole is one of a handful the city is dealing with right now.

"So under the roadway, most folks may not know that the majority of utilities are actually stored underneath the roadway. So often we see a leaky pipe or a water main that is leaking. In the instance of Crowchild, we had cameras and water crews go down there. It turns out there are no pipes so it must have just been underground water moving."

He says sinkholes happen in every quadrant of the city.

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