November 15, 2006

IAIN ROSE

The demolition of the Vancouver Woodward, done by implosion, went well despite a few windows that were blown out by the blast.

IAIN ROSE

When the blast came, it only took 25 seconds for the synchronized detonation to bring the building down.

Blasting

Strong structure no match for detonations

Burnaby company used 35 staff to set up blast

JEAN SORENSEN

staff writer

VANCOUVER

An explosion that took down three outside walls of the old Woodward’s department store created a mighty bang, a fitting last salute to the downtown Vancouver landmark store that had served generations.

“The explosion was extremely loud,” says Wayne Rawluk, demolitions manager for Pacific Blasting and Demolition, a Burnaby-based company that had 35 personnel on site to create the precision-timed blast.

The loudness of the blast resulted from the rigorous way the structure had been built.

“It was a very unique building,” says Rawluk, explaining it had no sheer wall offering support but rather a series of steel-core, concrete-encased columns with support beams holding up the building.

The construction method made the building extremely strong and the first of its kind that Rawluk had encountered in British Columbia.

Support columns presented a challenge as detonations, usually planted inside support columns in order to muffle noise, had to be planted on the outside of the columns. In total, 46 support columns were taken out with a charge set on the top and bottom of each, for a total of 92 detonations. Blast boxes were built to mitigate noise and flying debris.

When the blast came in a series of timed detonations at 8 a.m., it took only 25 seconds to bring the building down, says Rawluk.

Three walls represent 29 per cent of the building’s mass.

The remaining 71 per cent – the interior core – was removed using traditional excavation methods. This allowed Pacific to separate the three walls from the 1903-1908 heritage structure so it can remain on site.

“That gave us three sections for an easy implosion,” says Rawluk. The decision to implode (collapse inward) the three high walls facing busy streets was made because of constraints of the site, such as close proximity of other buildings and the high vehicle and pedestrian traffic at the site, which gateways the city’s Gastown area.

Explosives were only put in the basement and timed to create a “roll-over” effect of the walls on site.

Detonations on walls facing two of the streets went off at half-second volleys between the two walls.

“It was almost simultaneous,” says Rawluk, but not quite. Once the supports for these two walls were collapsed inward, the detonations on the Abbott street side started and caused the last wall to roll over, crumbling down.

“It was a perfect implosion,” says Rawluk, crediting his crew, the work done by general contractor Intertech Construction and project developers Westbank Projects/Peterson Investment Group in putting it together.

The City of Vancouver purchased the Woodward’s building from the B.C. government in March 2003 and in Sept. 2004 chose Westbank Projects/Peterson Investment Group as site developers, with Henriquez Partners as architects to develop a mixed-use commercial residential building that will still preserve the original Woodward’s structure built in 1903 and 1908.

Michael Flanagan, the city’s project manager on the new Woodward’s site, said he was pleased the implosion had gone well, despite a few windows that were blown out by the blast.

“It was a good day for the glaziers,” he says, adding 15 glaziers were brought onto the site as a pre-caution. A short video on the implosion is available on the city’s website of the Woodward’s project.

The demolition is now complete and the Woodward’s project is now moving into obtaining development permits.

Flanagan says site excavation and staging permits are being issued however, it is expected that the over-all development permit might be delayed two weeks because of the work volume in the industry today.

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