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A 120,000-tonne silo structure at the former Consumers Glass Chisholm Drive facility in Milton refused to bow down to 90 kilograms of carefully placed explosives.
GRAHAM PAINE, MILTON CANADIAN CHAMPION
Well-placed explosives didn’t quite finish the job when a series of silos at the former Consumers Glass plant in Milton were slated for demolition last week. ABOVE: The first blast set the silo in motion. RIGHT: The demolition contractor, Greenspoon Specialty Contracting, had to bring in heavy equipment to finish the job when the silo remained standing — more or less.
Demolition
MILTON
A 120,000-tonne silo structure at the former Consumers Glass Chisholm Drive facility in Milton refused to bow down to 90 kilograms of carefully placed explosives.
The 120-foot structure, once used to store sand used by the glass manufacturer, was scheduled to come down last Friday morning. Instead of keeling over, the silo settled comfortably in its own debris at a precarious angle. About 400 disappointed spectators gathered to watch the event.
“It was the strangest thing,” says Robert Hamilton, president of Greiner-Pacaud/Hamilton Inc., a partner with Greiner-Pacaud Management Associates in redeveloping the 22-hectare industrial property.
“It began to tilt over and then came back again.”
Why didn’t the structure come down as planned?
“There were a couple of support columns that probably should have been cut,” says Fred Topley, Senior Project Manager with Greenspoon Specialty Contracting.
“We have to leave those decisions up to the engineers at the blasting company we sub-contracted. We drill the holes and we pack the dynamite, but it’s all according to their plan.”
The explosion was engineered by Explotech, an Ottawa engineering company specializing in explosives and blasting, and Dykon Explosive Demolition Corp. of Tulsa, Oklahoma.
“The elevated building was supported by three rows of supporting columns,” says Rob Cyr, an engineer with Explotech. “We first took out the front ones, and then blasted the back row. It’s like creating a notch in a tree you’re chopping down. Before it had the chance to pivot on the remaining centre columns, the structure collapsed into the debris. If it had tilted over an additional two degrees it would have fallen over.”
The blast had taken a month to plan and prepare, so additional blasting wasn’t an option.
“There are no guarantees with this type of demolition,” adds Cyr. “Things don’t go exactly as planned about 20 per cent of the time.”
The Greenspoon demolition team immediately switched to Plan B, using construction equipment to remove some of the non-structural components of what had quickly been dubbed “the leaning tower of Milton.”
“We had a surveying scope about a thousand feet away,” says Topley. “We watched it all day on Saturday and it didn’t move until we broke the structural supports, so it came down when we were ready for it.”
The team of backhoes finally persuaded the tower to come to Earth on Saturday evening.
“Taking down buildings by machine is our area of expertise,” says Topley. “And demolishing the structure this way was one of our original options.”
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