Sinking into permafrost, Ross River School needs more repairs

Engineers are recommending that the Ross River School be relevelled again, just two years after a round of major repairs.

Engineers are recommending that the Ross River School be relevelled again, just two years after a round of major repairs.

Reports from earlier this year show permafrost under the school continues to warm, causing the building to move.

In 2015, the school was shut down for months and repaired after the building was found to be so badly damaged it was deemed unsafe.

“Common sense would dictate that when you’re spending millions of dollars on a fix for a school, that it’s going to last longer than two years,” said Highways and Public Works Minister Richard Mostyn.

“That would be my expectation as a Yukon citizen.”

Mostyn said his department is coming up with solutions for the school. All options, including building a new school, are on the table, he said.

“There are many options. I’m sure building a new school is one of them. I’m sure there are many others as well.”

The Ross River School was constructed in 1999 and 2000 on permafrost.

By 2002 it was already showing signs of distress “such as cracks in walls and sloping floors,” an engineering report from March 2017 says.

“Monitoring of ground temperatures indicated that the permafrost was retreating under the school.”

The school’s foundation is supposed to be kept cool in part with the help of contraptions called thermosyphon loops. Those are meant to pull heat away from the building foundation and surrounding soil.

Even with the thermosyphon system in place multiple reports over the years show that the building’s crawlspace is still too warm.

A report from January 2015 says the temperature in the crawl space was 17C.

“This is extremely high for a building utilizing thermosyphons to provide foundation stability. Crawl spaces above a thermosyphon system generally are required to have the same temperature as the outside air,” it says.

“High temperatures in the crawl space are considered to be the major cause of the permafrost degradation under the building.”

When engineers visited the school in March 2017 the crawl space had cooled to an average of about 7C, still slightly warmer than it should be, the newest report says.

“History has shown, however, that these temperatures can only be achieved in the winter — there needs to be a way to get summer crawl space temperatures colder.”

Mostyn said the thermosyphon system is not working.

“If the thermosyphon system was working, (the school) wouldn’t need to be relevelled,” he said.

To get any sort of permanent stability, the permafrost needs to refreeze, according to the latest report.

One option is to install refrigeration units that would refreeze the ground.

“Once the active layer under the school has been re-established in the sand and gravel, the mechanical system could be disconnected (but not removed) as the thermosyphons should be able to maintain the permafrost per the original design,” the report says.

That price tag is estimated at $500,000.

It’s not clear how much money has been spent on the school to date. The department is coming up with a total, Mostyn said.

Parts of the school were first relevelled in 2006 and more thermosyphon loops were installed. In 2013 the crawl space got improved insulation.

Geotechnical engineers have been monitoring the school twice a year ever since it was shut down in 2015.

The government spent about $1.8 million on repairs and relevelling that time around.

The bids came in over budget and geotechnical work was removed from the original request. Officials told the News at the time that work would be part of a separate tender.

Mostyn said he’s asked for more information on that work.

None of the department’s engineers were available for comment.

In 2015 an engineering report warned the problems at the school wouldn’t be fixed permanently until the ground was stabilized.

“If the foundation has not stabilized and further movement/settlement are allowed to occur, any repairs carried out should be considered as a temporary solution only.”

The reports came before earthquakes shook the territory earlier this month.

Structural engineers came to the school and ruled it was safe to occupy. That engineering report is expected to be made public May 12.

Contact Ashley Joannou at ashleyj@yukon-news.com.

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