Ross River school structurally sound, says engineers' report

Yukon's Minister of Public Works says students will be back in class at the Ross River school this fall after two engineering firms report the school is structurally sound.

Wall cracks, poor-fitting doors 'irritate users' but don't mean the building is unsafe, says minister

Yukon Public Works Minister Richard Mostyn says he trusts engineers' word. 'These are experts in their field. We've had them look at this building and they say the building is safe,' he said. (Philippe Morin/CBC)

Yukon's Minister of Public Works says students will be back in class at the Ross River school this fall after two engineering firms report the school is structurally sound.

The school has had visible cracks in interior walls and damage to concrete supports. So far the territorial government has paid for renovations in 2004, 2006, 2013 and 2015. 

"All the engineers who have been on the site have told us that the school is structurally safe and sound," Richard Mostyn said.

Mostyn said the engineers' consensus is that the shifting of the foundation doesn't threaten the structure.

It does however, point to recurring problems caused by permafrost that the school's original design has not been able to mitigate.

These concrete pillars were repaired in 2015. The school in Ross River has had problems for years, due in part to its supports sinking into the permafrost. (Yukon government)

"We've all seen pictures of cracks, windows that have cracked, doors that won't shut properly," he said.

"These are functional problems. They irritate users and make the building less efficient but they don't make the structure any less safe."

Mostyn acknowledged that some people may be feeling apprehensive about the building's safety. However he said the engineers' recommendations are clear. 

"These are experts in their field," he said.

"We've had them look at this building and they say the building is safe. They put their stamp of approval on it. To me there's no greater endorsement than that.

"That's the certainty I wanted when I started this whole process. And I am going to take their professional advice and I am going to stand behind it." 

The two engineering firms hired by the Yukon government in June were David Nairne and Associated Ltd., a structural engineering firm dealing with buildings, and Thurber Engineering Ltd., a geotechnical engineering firm that deals in the analysis and construction of foundations. 

Climate change

One question is whether the school was designed properly for permafrost conditions in a changing climate.

Mostyn said the government is pledging to evaluate the thermosiphon system installed below the school during its construction in 2001. These kinds of systems are designed to insulate and maintain permafrost under heated buildings.

"We don't know if these thermosiphons don't work or if there just wasn't a robust enough system to deal with the changing climate," Mostyn said.  

The engineers' report cites some design problems. It says problems since 2002 can be attributed to "degradation of the permafrost due to warm crawlspace temperatures, roof runoff water and a general warming trend in the air temperature since the construction of the school." 

Cracks like these are not a sign of structural damage says Yukon Public Works Minister Richard Mostyn. 'These are functional problems. They irritate users and make the building less efficient but they don't make the structure any less safe," he said. (Billie Maje)

Stabilizing the permafrost

Both engineering firms say there is no risk of collapse. However they call for a "long-term strategy to ensure the continued structural safety of the school." 

Mostyn said this could include a freezing system installed to stabilize permafrost under the building. However he said the concept still needs more research to determine if it is "technically viable and financially responsible."

Other options could include a new foundation. Mostyn said "more drastic measures," such as replacing the school will only be considered if these mitigation measures don't work or prove too expensive to consider.

For the time being, he says there's no reason for students and staff to avoid the building. 

The territorial government will install sensors to detect motion and changes in temperature below the school. It's also pledging physical inspections twice a year.

Yukon Education minister Tracy-Anne McPhee is pledging to keep people informed on what's decided. 

​"We're satisfied we have the information we need right now for school to go ahead, but we want to be in communication with the community we want to deal with all of their concerns," she said.