Mysterious car-sized concrete mass delays LRT bridge construction over river

The unexpected discovery of a concrete mass the size of a car, nine metres below the surface of the North Saskatchewan River, is delayingconstruction onthe Tawatin 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 massgot there.

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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 down12 metres to secure the bridge support.

Complicated logistics

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," Edeensaid.

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, asTransEd 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.

TransEd is considering several corrective measures, but won't know which one to use until the obstruction is fully uncovered,Edeensaid.

"We won't know specifically what we are going to apply until we actually see what's down there," he said.

The delays will affectthe shared-use path that will be part ofthe Tawatin Bridge. The path won't be open in May 2019, as originally planned.

TransEd will face financial penalties relating to the delay in opening the shared use path, but the amount was not disclosed.

LRT construction still on track

The company saidtheunexpected development should not prevent the Valley Line from opening on time in 2020.

Construction will ramp up during the rest of 2018, with rail beds and stations taking shape. The work will have a major impact on traffic, from Mill Woods to downtown.

Construction will start on the west side of 75th Streetand should be completed by the end of the year.

Whitemud Drive will be closed on two weekends, as crewsinstallthe infrastructure that will support the Valley Line. The exact dates will be known later this spring.

Connors Road will close temporarily, as utility work gets underway in March and April. The road will reopen, but will be down to three lanes for the remainder of the LRT construction.

Construction work will also start along 95th Avenue, preventing residents from parking along it. There will be alternating lane closures that will disrupt traffic.

In the downtown, 102nd Avenue will remain closed while utility and drainage work is completed. Work on the tunnel should be completed later this spring.

Open houses will be held from March 17 to 28in communities affected by the construction.