Maple Leaf Gardens renovation requires surgical demolition

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.

Crews are busy 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,” said 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 about 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 month.

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, said 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 as well as trusses on the north and south walls before the demolition could begin, said Priestly.

A structural analysis of the slab also revealed that 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 used.

One of the more delicate operations was removing the four levels of VIP box seats 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 that they didn’t come into contact with the walls, said Priestly.

About 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, said Priestly.

“It was difficult to move there for awhile,” said John Phillips, vice president of operations for Priestly Demolition.

When the project wraps, they will have removed and trucked about 11,000 metric tons of material, including 8,500 tons of concrete, said Phillips, adding that 92 per cent of it will be recycled.