September 15, 2009
Repair of Canada's busiest bridge slated to finish one year early
When it comes to massive road and bridge repairs, it doesn’t get much bigger than the current work being done on the Hogg's Hollow bridge.
Given the nature of the $84 million project to repair the twin 378-metre-long bridges some 80 metres above the ground, including widening, replacing gussets, bearings and laces, and pouring new slabs and laying new asphalt, you’d be forgiven for thinking the 2013 completion date might be delayed.
But innovation, collaboration and a steady work crew have combined to knock a full 12 months off the length of the project, which is now expected to finish in 2012. That’s a full decade after work started in in the area — first at Bayview Avenue, then the Yonge Street bridges and now the big span — which will see a total $160 million investment.
“We’re going six days, some 60 to 65 hours a week,” says Mick Dowling, Brennan Construction and Paving’s structures superintendent.
“We started pouring a slab a week and we’re up to two. We also figured out a faster way to do it which is saving us time. I’ve got a good crew — many of them have been working with me for years on these 400 series of highways.”
And the current work is built to last.
With some $12 million in stainless steel rebar wired into the mix, “this is going to be good for 100 years,” Dowling says with an air of confidence.
It’s a bold statement considering the original bridge that carried the old Yonge Boulevard over the leafy ravine was completed in 1929 and the sister unit was constructed in the 1960s when Highway 401 was being built. Both have been the subject of extensive work over the years, hardly surprising given the two million trucks, cars and motorcycles a day thundering over them
Dowling’s got a crew of about 70 men working on the project, which involves both topside and underside work. While the earlier bridge is concrete and steel, the more recent structure is steel and needs extensive work to replace rusted sections. The older bridge will also need a scrape and repaint of the steel spans.
“There are 32 bearing points and we need to raise each one up just enough to get a new, stronger one in there,” says Greg Harrison, of URS, contract administrator on the project for the Ministry of Transportation Ontario.
“We’re also going to be reducing the number of slabs and expansion joints using link slabs (modified concrete with fibre) which will add to the lifecycle, since you won’t get as much salt in there with the corrosion. There were 11 expansion joints before and we’ll be down to seven.”
It’s been a logistical challenge given the live traffic considerations at the busiest point of Canada’s busiest highway.
What’s striking about the job site is the contrast between the two levels: the top deck where the roar of traffic and the weather are always a factor and the relative quiet and stillness of the lower structural steel where a platform has been built to allow easy and safe access.
“After a while you just get used to the traffic,” says Dowling even as the bridge deck noticeably trembles under the onslaught of wheels trundling across it. “The guys don’t even notice it anymore.”
What they did notice, however, was the odd bra or panties flung in their direction by passing motorists, perhaps as homage to their efforts.
Still, there were a few unique challenges to the site, he admits, not least of which were the infestation of raccoons on the underlying structural steel. With the bridge spanning a wooded ravine and a city-owned golf course, the critters were everywhere.
With men working and the promise of food in the form of lunch leftovers, the raccoons descended with a vengeance, leaving their dropping in massive quantities.
“It was a health and safety issue because they carry disease of course, so we had to do something to clean up and disinfect,” says W.S. (Bill) Kennedy, MTO’s Area Construction Engineer.
While the masked bandits caused issues down below, two-legged bandits were at work on the deck. Initially there was also some shrinkage in the inventory of stainless steel rebar which was selected for its obvious corrosion-resistance. Given the price of steel, it wasn’t surprising that some went walking but that’s since been solved, says Harrison.
Harrison and Kennedy have also been working with the local councilor and community to ensure that the work encroaching on the properties bordering Highway 401 is suitably cleaned up and that the new sound barriers — textured stone that’s higher than the exiting barriers and with better sound-insulating properties — sit well with residents.
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