Downtown sinkhole road closure to continue into this week

Downtown Calgary drivers and pedestrians must continue to make a detour around a sinkhole that will keep a busy road closed until later this week.

The sinkhole a hole or depression in the earth that can be caused through erosion was discovered on Friday evening at 4th Street S.W. between 10th and 11th Avenues.

The city closed a section the street on Friday and planned to have it reopen by Wednesday, but officials now say it may take longer to find out exactly how big the sinkhole is, and how to fix it.

City officials estimated Monday that the sinkhole is about six cubic meters. The crater, about eight metres below street level, is believed to be directly underneath several lanes of traffic.

The sinkhole is right next to the Gateway-Midtown condo project that was abandoned by its original developer in August. Its new owner, Point of View Developers, told CBC News it's proceeding with construction of a twin-tower condo complex. Its engineers are working with city staff on the sinkhole problem.

Sinkholes are generally caused by water flowing underneath the surface, but fixing them is not as simple as just filling them in with dirt, said the city. Kevin Griffiths, chief building inspector for the City of Calgary, said solutions that must take into account the stability of the site and the road are complex.

"We do know that water is a factor, a contributing factor, so the sooner that you can stop the flow of the water, or the water flow affecting the soils adjacent to the site in the way that it has affected them then that would be the solution but again, we won't be able to say until we have the report," he said Monday.

With at least nine abandoned construction sites in the Beltline area, city officials said they're monitoring the situation.

"This sinkhole situation, location of it, would indicate that it would probably have minimal effect on those buildings, but we are concerned if there's any other sinkholes or similar issues around that sites," said Griffiths.