November 25, 2010

PRIESTLY DEMOLITION

Crews work to break up the cement ice pad to excavate an underground garage.

FEATURE | Demolition & Environmental Engineering

Maple Leaf Gardens renovation requires surgical demolition

DAN O’REILLY

correspondent

Toronto’s former hockey shrine is undergoing a massive and sequenced gutting that is almost unique as the building itself.

After sitting vacant and boarded up for almost a decade, Maple Leaf Gardens is a beehive of pre-construction and demolition work transforming the classic arena into a 70,000-square-foot Loblaws grocery store at the street level and a sports and recreation centre for Ryerson University on soon-to-be built upper floors. Its art deco exterior is being left intact.

“This is not a common job for us,” says Brian Priestly, superintendent with Priestley Demolition Inc., which is conducting the sequenced and careful interior renovation.

It has included asbestos abatement, ripping out hundreds of seats, breaking up and removing the concrete slab and an approximately 20-foot-deep excavation below the slab level to make space for an underground garage. The project started in December 2009 and is scheduled to wrap up this December.

Unlike many of its projects that are complete demolitions of entire buildings, the work at Maple Leaf Gardens is an inside operation that can’t touch, penetrate or jeopardize the exterior concrete walls, says Priestly.

A computer monitoring system installed by Buttcon Construction, the general contractor overseeing the project, “measures every stress and strain on the building.”

The general contractor also erected supporting braces along the east and west walls and trusses on the north and south ones before the demolition could begin, says Priestly.

A structural analysis of the slab also revealed it wouldn’t support heavy machinery, which meant that only small bobcats and mini excavators could be used. A 200-ton conventional crane, a 55-ton hydraulic crane and two high- reach excavators were use “to chew back the building.”

One of the more delicate operations was removing the four levels of VIP box seas that went around the entire arena. After the seats were torch cut they were carefully lifted down to the slab by the crane operators who had to be extra vigilant they didn’t come into contact with the walls, says Priestly.

Approximately half of the onsite work force of 50 people was involved in the asbestos abatement, which was conducted concurrently.

Last April, the bulk of the demolition had been completed and the project moved into the excavation for the underground garage. This phase of the work included removing the bottom halves of the arena’s columns. The general contractor is replacing them with longer and thicker columns, which increase the structural loading capacity, says Priestly.

“It was difficult to move there for awhile, says John Phillips, vice- president of operations for Priestly Demolition. When the project wraps, they will have removed and trucked some 11,000 metric tons of material, including 8,500 tons of concrete, says Phillips, adding that 92 per cent of it will be recycled.

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