As reported on CBC news, the unexpected discovery of a concrete mass the size of a car, nine metres below the surface of the North Saskatchewan River, is delaying construction on the Tawatinâ Bridge, a crucial structure for the Valley Line LRT.
“It’s been a huge challenge. We encountered this mass, we didn’t even know it was a mass,” said TransEd spokesperson, Dean Heuman. “We kept trying to drill through it, thinking that it would break up. It just never has.”
No one can explain how the mass got there.
Crews discovered it in the fall while building a cofferdam, a structure that holds back water while construction takes place.
The concrete mass is located below the platform that will hold the north pier of the bridge. Crews need to dig down 12 metres to secure the bridge support.
Removing the obstruction would cause safety and environmental concerns, according to the project manager for TransEd, Will Edeen.
“We’re having to use different techniques for the safety of the workers and the environmentally sensitive aspect, because we are in the river valley, we are working in the river bed,” Edeen said.
Experts with experience building cofferdams in difficult conditions have been on site since February to develop a safe technical solution for working around the obstruction, he said.
The solution isn’t obvious, as TransEd still doesn’t know exactly how big the mass is.
Crews are slowly digging their way down, but have to be cautious because the cofferdam isn’t as deep as it should be.