Crews demolishing the old F.H. Collins High School in Whitehorse have uncovered more contamination than anyone was expecting.
Hidden leaks from the school’s oil fire heating system and underground fuel tanks have contaminated the soil and reached the groundwater. City staff said Whitehorse’s drinking water is not believed to be at risk.
Officials blame the mess on two underground fuel tanks from the 1960s that were eventually removed in 2009.
Fuel spilled from the tanks 2008 and 2009. Crews cleaned up as much as they could at the time, but knew that some of the contamination had seeped under the school.
“Some had gotten underneath the foundation,” said Shannon Trott, the acting director of facilities management and regional services with the Department of Highways and Public Works.
“To remove (soil) from underneath the foundation would cause some foundation concerns which is not safe for our students.”
Crews demolishing the school earlier this month were expecting to find about 100 cubic metres of contaminated soil left behind under the school.
Instead they’ve removed about 300 cubic metres as of June 28 and the work isn’t done yet. It’s too early to say how much soil will eventually have to be taken out.
“We’re chasing the contamination as we go,” said Amanda Janssens, the manager of Environment Yukon’s site assessment and remediation unit.
The problem is bigger than the spills in 2008 and 2009. The old heating system had developed pinhole-sized holes in lines that went underneath the foundation.
No one knows how much fuel leaked from those holes, or how long the leaks were going on, before the tanks were removed.
The F.H. Collins site is about 400 metres from one of the wells connected to the Selkirk Aquifer, the source of the City of Whitehorse’s drinking water.
Water samples are going to be tested, but “there is no indication of hydrocarbons in the (drinking) water,” said Peter O’Blenes, the city’s director of infrastructure and operations.
“From a city standpoint, we’re very confident that this is a low risk.”
The contamination has gotten down to the shallow groundwater table, about 6.5 metres deep. Fuel won’t travel any deeper once it hits water, Janssens said.
The aquifer is at a depth of 22 to 44 metres.
Based on the way the groundwater flows, any contamination would be pushed away from the aquifer well, not towards it, officials said.
Dr. Brendan Hanley, the Yukon’s chief medical officer of health, agreed the risk to the public’s health is low. Even a small amount of fuel is easy to taste or smell when it is in drinking water, he said.
“You actually would have to drink several ounces of fuel in order to get a toxic affect because the body, through the liver, is so efficient at getting rid of it.”
Janssens said it should take another three or four weeks to clean up the contamination.
The priority is to remove the contaminated soil because it can be a source for contaminating the ground water, she said.
“It’s very difficult to pull all of the contamination out of the ground water,” she said.
“As we remove the soil we will be de-watering which means we will be pumping water out of the base of the excavation as we encounter it (water).”
Soil will be sent away to be treated. It’s too early to say how much the process will cost, she said.
The territorial government is in the middle of removing all underground oil tanks from government buildings.
Fifteen tanks have been taken out over the last few years, Trott said. None of those systems had the same pinhole damage in their lines that was found under F.H. Collins, she said. Four more tanks are expected to be removed this year. The department says there are about 25 tanks left to be taken.
The City of Whitehorse is in the process of coming up with a bylaw to ban underground fuel tanks.
That is likely to come before council in the new year, O’Blenes said.
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