Nalcor, Astaldi hire outside help to investigate Muskrat Falls collapse

Nalcor Energy and Astaldi Canada have both hired outside companies to help investigate a concrete formwork collapse that rattled workers and temporarily forced the shutdown of a portion of the massive worksite late last month.

• Concrete collapse at Muskrat Falls megaproject under investigation

CBC News has also learned that a Kansas-based company called Contractor's Engineer Inc., also known as CEI, designed and manufactured the specialized formwork used to fabricate the critical draft tubes in the powerhouse.

Officials with CEI have not been available for comment, but engineers hired by the company are involved in the investigation.

Equivalent of 17 basements

A handful of workers were covered in wet concrete but escaped injury after the plywood formwork in draft tube No. 2 failed during a pour near midnight on May 29.

Some 500 cubic metres of concrete was spilled, which is the equivalent of about 17 concrete basement for an average sized home.

Plans call for four draft tubes to be built, and the first one was completed without incident.

All work in the draft tube area of the powerhouse has been suspended while an investigation is carried out.

It's not known how long the investigation will last, or what it will mean for the massive project, which is already behind schedule and over budget.

Nalcor CEO Stan Marshall said Wednesday he doesn't expect the incident will dramatically alter the construction schedule.

"I don't think it will be many months, but I don't know," he said.

"Until we know what the root cause of the problem was, we don't know what the cost of resolving it will be. Maybe it was some simple defect. Maybe there's something wrong in the design. Who knows?"

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The draft tubes are essentially large concrete pipes that return water to the Churchill River after it runs through the power turbines.

Nalcor has contracted a Vancouver company called ADB Structural Engineering, which specializes in the design and engineering of temporary and specialty structures, to help with investigation. Two other companies, Hatch and SNC-Lavelin, are also involved, a Nalcor spokesperson confirmed Wednesday.

An official with Astaldi confirmed that clean-up at the site has not yet begun, though the plan calls for the use of industrial drilling equipment to remove the hardened concrete that spilled last month.