February 12, 2009
Water tank demolition in Orillia, Ontario a tight fit
A 26-metre water tower bearing the city’s name has stood in Orillia for more than 50 years, but the decaying landmark was beginning to wear out its welcome. One of the challenges to its demolition was that the six-legged tower stood on a small lot, about 21 by 46 metres, surrounded by residential housing. If the tower were toppled, it could have caused damage to surrounding properties built in its shadow.
The Benner Street tower was originally erected in 1956, but had been mothballed 30 years later.
“When the city grew westward we put in another reservoir and the tower became redundant,” says Bruce Duncan, Manager of Property & Purchasing with the City of Orillia.
But the tower had one saving grace. As one of the high points in town, it housed a communications antenna that served the RCMP and local fire departments, the city’s Supervisory Control And Data Acquisition (SCADA) system and other clients.
“It was starting to become an eyesore and I knew in the back of my mind that it had to come down some time,” says Duncan. The plan of attack was initiated with the construction of a brand new 50-metre communications tower next door to the structure.
“It offered much better communications capability and our clients were much happier to see it built,” says Duncan.
The city issued a tender with the proviso that the successful bidder would have an impeccable safety record and that an outside engineer would approve the job plan. “We wanted to have a plan in place that was completely acceptable to the Ministry of Labour,” says Duncan. “We received six or seven bids but the low-bidder, at $40,000, was Progreen Demolition Ltd. They came highly recommended — even their number one competitor had nothing but good things to say about them.”
The Concord-based contractor embarked on a top-down strategy to first dismantle the 250,000-gallon (1.136-million-litre) tank.
“They started by torching semi-circular holes in the base of the tank, then removed the catwalk around the exterior,” says Duncan.
Progreen used a high reach hydraulic shear to remove smaller sections of the tank, twisting them back and forth until they came free.
“The top was taken off with extreme precision,” says Duncan. “There were a lot of discussions about the way in which the tower would be taken down. They maintained the integrity of the tank until it no longer represented a hazard.”
The supporting legs were removed in sequence, leaving only a small utility shed and an underground main to finish off the demolition job.
Duncan recorded the demolition in a series of photographs taken over the length of the two-week project, which went off without a hitch. About 200,000 tonnes of steel were salvaged from the job, for sale to a scrap metal dealer.
For Orillia residents, a new communications tower dominates the skyline, instead of a rusting metal hulk.
“The site is now completely clear,” says Duncan. “All that’s left is about three feet of snow.”
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