A structural engineer has been disciplined for making "material errors" and miscalculations that contributed to the collapse of a wooden formwork at Muskrat Falls in May 2016 that resulted in a near-miss for a group of workers.

Peter Liu of Ontario has been stripped of his right to practise engineering in Newfoundland and Labrador by the province's association of engineers and geoscientists, a group known as PEGNL.

'Conduct deserving of sanction'

The decision was part of an April 25 ruling by an adjudication tribunal, the first in more than two years in this province, and is the latest development for a troubled project that is now at the centre of a long-running public inquiry because of massive cost and schedule overruns.

This image shows the draft tube before the May 2016 collapse. (Nalcor)

In an agreed statement of facts, Liu admitted he engaged in "conduct deserving of sanction, professional incompetence and/or conduct unbecoming a professional member or permit holder" under the Engineers and Geoscientists Act.

The discipline relates to a May 29, 2016, incident at the powerhouse in Muskrat Falls in which a portion of the wooden formwork for a concrete structure called a draft tube collapsed.

"When there are public structure failures like this it gets our attention and we take it pretty seriously. This led to us investigating the matter and to our disciplinary process being put in place. And you can see the result," said Geoff Emberley, PEGNL's CEO and registrar.

Liu was employed by Astaldi Canada, which was building the powerhouse and spillway for Nalcor Energy.

Part of the project included the construction of four sets of draft tube formworks and related supports, which Astaldi sub-contracted to U.S.-based Contractor's Engineer Inc., or CEI.

There are four draft tubes at the Muskrat Falls generating station, beneath each of the four power turbines. The concrete tubes will direct water away from the powerhouse after passing through the turbines. The wooden formwork for draft tube No. 2 collapsed May 29, 2016 during a major pour. (Nalcor)

During a massive pour of concrete nearly three years ago, the formwork on draft tube No. 2 failed, resulting in five workers falling into the wet concrete mixture, completely submerging one of the workers.

The formwork was designed and fabricated by CEI and installed by Astaldi.

An investigation found that the design of the draft tube elbow formworks was "not based on sound engineering judgment" and there were "inconsistent and incorrect loading calculations."

This is a recent aerial view of the Muskrat Falls project in central Labrador. The project is more than 90 per cent complete, with first power forecasted for late 2019. (Nalcor)

In reviewing, approving and stamping the design drawings, Liu "failed to identify and take necessary followup action pertaining to the use of incorrect design criteria by subcontractor CEI, which failed to adhere to the use of Canadian codes and standards," the tribunal found.

Liu was employed as an assistant project engineer with Astaldi, but was laid off by the company in late 2016. His licence to practise engineering in the province expired in March 2017.

Astaldi is suing CEI over the incident, with the matter still before the province's supreme court.

An external investigation on behalf of Nalcor found that "deficiencies in the shoring system" used to support the formwork contributed to the collapse.

In order to have his licence reinstated in the province, Liu would have to complete various training courses. He was also ordered to pay $5,000 to cover a portion of the hearing costs.

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