A Canadian renewable-power company will replace foundations at a New Brunswick wind farm after engineers determined a turbine collapse in October stemmed from design flaws.

TransAlta Renewables Inc. said replacing 50 foundations will cost $75 million to $100 million (US$59 million to US$79 million) and take until the end of 2023. The Calgary-based company expects to lose $3.4 million per month in revenue while the turbines are off line, according to a statement Tuesday.

The foundation problems are limited to the 50 turbines at two sites in Kent Hills and there’s no indication of similar issues with the company’s other wind farms. TransAlta has more than 20 wind facilities in Canada and the U.S., according to its website. 

It’s rare for wind turbines to fall down, but it happens. A 230-meter (755-foot) one built by Vestas Wind Systems A/S collapsed in northern Sweden in 2020, and a 239-meter turbine in Germany fell down last year. The TransAlta failure in New Brunswick, however, is worse because foundations for the entire wind farm need to be replaced.

After the collapse of a Nordex turbine in Germany last year the company temporarily shut down 22 turbines with identical configurations until the cause of the failure was determined, according to the company. 

TransAlta shares fell as much as 11 per cent Tuesday, the most since March 2020. TransAlta Corp. launched TransAlta Renewables in 2013 and is its largest shareholder. TransAlta Renewables owns interests in wind, solar, hydropower and natural gas facilities.

Wind farm operators don’t often disclose when they shut down so it can be difficult to know the consequences of a failure or collapse, according to Oliver Metcalfe, wind industry analyst at BloombergNEF. 

The company sent notice to BNY Trust Company of Canada, trustee of the $222 million in outstanding non-recourse project bonds, that “events of default may have occurred under the trust indenture governing the terms of the bonds.” 

Bondholders of more than 50 per cent of the outstanding principal amount have the right to immediately collect what is owed them. The company is negotiating with the trustees and bondholders to head off this possibility.