Nfld. & Labrador

Muskrat Falls cofferdam, North Spur get passing grade in engineering report

A review by Hatch of dam safety at Muskrat Falls in Labrador says facilities there meet Canadian safety standards.

Cofferdam design 'is robust such that catastrophic failure of the structure would not be expected'

A downstream view of the Muskrat Falls spillway. (Nalcor Energy)

A safety audit done at the Muskrat Falls generating site in Labrador in late January and early February has concluded that Nalcor's dam safety management program meets or exceeds industry standards.

The report, done by engineering and consulting company Hatch from Jan. 29 to Feb. 2, followed leaks from a temporary upstream cofferdam, and concerns expressed by area residents about the stability of the North Spur.

"Current levels of leakage [are] in line with what would be expected for a cofferdam of this type," the report said, adding that remediation measures — grouting — are appropriate and "appear to be effective."

The cofferdam design "is robust such that catastrophic failure of the structure would not be expected," Hatch reported.

The cofferdam at Muskrat Falls, as seen in November 2016, leaked on first use but is being repaired. (Nalcor Energy)

The audit noted that a monitoring plan involves 12 measurements daily. It said alarm levels are adequate but could be reviewed.

As for the North Spur, Hatch said monitoring exceeds industry best practices, but alarm levels could be updated.

Overall, Hatch gave Nalcor high marks for dam safety, emergency preparedness and staff training, and said the probability of a significant safety risk is very low.

It said developing issues could be identified through weekly comprehensive inspection reports and monthly evaluations.