December 21, 2009

With the Queen Elizabeth Way shut down, six machines completed the demolition in hours.

Demolition of Ontario bridge takes hours, not days

PETER KENTER

correspondent

In the brave, new world of highway bridge demolition, projects are scheduled over hours, not days. The Martindale Bridge crossing the Queen Elizabeth Way (QEW) near St. Catharines, Ont. was no exception.

“We usually set some limits and allow contractors a specific number of hours to close the highway and get the work done,” said Ministry of Transportation spokesman Will Mackenzie. “In this case, we were scheduling 10 hours for demolition because of the wideness of the bridge.”

The overpass, constructed in 1939, once supported an intra-urban streetcar line that had long since gone out of service. The additional lane, running alongside the vehicle lane, was eventually devoted strictly to pedestrian and bicycle traffic.

“Because of that feature it was a unique bridge, but it didn’t have any particular historical significance,” said Mackenzie.

“After the streetcar line was taken out, the bridge still had that part of the deck.

“Today they would use continuous welded rail, but that wasn’t the case in the 1940s. Most of that type of rail bridge used what was essentially a viaduct filled with a gravel ballast and the track sections were laid on top of that. It allowed for a smoother track and was also easier for railway maintenance.”

The bridge was demolished to be replaced by a new span as part of a $183-million upgrade contract awarded to the Dufferin Construction Company to widen the QEW.

The contract represents the last remaining section between Toronto and Niagara Falls that has not been widened to six lanes.

“There simply wasn’t enough room to widen the highway underneath the bridge,” said Mackenzie.

“Originally, the contractor came to us with a plan to detour traffic around the abutment, but later they came to us and said they could do it faster and cheaper if we could close the highway for one night.”

A new single-span four-lane underpass structure was already under construction and ready to accept traffic as the old bridge was being demolished.

“The standard procedure is to begin by laying a foot-and-a-half to two feet of gravel on the highway to protect the existing road surface underneath from falling concrete and debris,” says Mackenzie.

Tonnes of cushioning material were laid down in the initial minutes of demolition. The contractor then sent in six excavators to attack the bridge simultaneously, as concrete was hammered to rubble and hydraulic cutters sheared steel rebar.

Backup units cleared away debris as the excavators progressed. In a few hours, the road was swept clean.

“The site was cleaned up and traffic resumed along the QEW at 10:00 a.m. on Sunday as scheduled,” said Mackenzie.

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