When the first inspection teams showed up at the Mc-Gill University Health Centre’s Glen Campus site back in April 2005, it was admittedly a complete mess.
There were decaying buildings, rotting piles of timber, rusty metal beams and all the detritus that usually accompanies an abandoned rail yard. The real concern, however, was what lay beneath all that junk.
Over the previous century-and-a-half, tonnes of industrial contaminants had slowly worked their way down into the soil, creating a major problem for construction.
"It was a CP rail yard, so there were hydrocarbons because of the trains and the maintenance that was done there," Pierre Major, the MUHC’s associate director of facilities development and construction, explained.
"Also, as the name suggests, the Glen wasn’t always flat. It was filled up at the beginning with leftover waste from industrial ovens, which is very compactable. That would have produced heavy metals that seeped through the soil."
The MUHC planning team had two options: Scoop out the hydrocarbons, then isolate some of the other contaminants, using a layer of unpolluted soil, or decontaminate the whole thing from top to bottom. It decided on the latter.
"For us, we would have always been left with the stigma that we built a 21st-century hospital on contaminated soil," Major said.
"It was worth the expense."
Nineteen months and $38 million later, Glen Yard was clean as a whistle.
The process involved creating a grid of squares, each measuring 25 metres by 25 metres, across the entire site. Then, in every square, workers took a soil sample one metre down at each of the four corners and in the middle.
The thousands of samples were sent to a provincially accredited lab, where they were tested for contaminants. If the samples in a square came back positive, a team of backhoes would scoop out that first metre of soil across the entire square. Then the process was repeated again and again in every square, until finally all the samples taken beneath the new surface came back clean.
In some sectors, workers had to dig out only two or three metres of earth. In others, 16 metres of soil was carted off to serve as a covering layer for garbage dumps -a practice approved by the Environment Department.
"We removed over 700,000 metric tonnes," Major said. "At the peak, we had about 150 trucks a day on the site.
"Many people don’t realize it, but this was the largest decontamination project in Quebec’s history."
Once it was all over, crews drilled holes all the way to bedrock to double-check that there weren’t pockets of contaminants farther underground.
Major said the site now is considered a "green field" by the provincial government, meaning all the elements in the soil are classified, in industry jargon, as "AB" level.
"Whenever you’re in ‘AB,’ it’s safe," he explained.
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