Feature – Fall of Empire

For more than 40 years, the Empire Landmark in Vancouver, Canada, held the title of the city’s largest free-standing hotel. The structure, capped by the iconic Cloud 9 restaurant, defined Vancouver’s skyline. But when developers decided to revitalise the city’s West End, the Landmark’s time had come.

However, demolishing a building on one of the city’s busiest thoroughfares – without bringing local traffic to a standstill or risking people’s health and safety – would require creative engineering from the appointed contractor. Environmental and demolition specialist JMX Contracting accepted the challenge. Using robotic demolition, JMX systematically removed 44 storeys, a total of almost 40,000 sq m (430,000 sq ft) of floor space – in 21 months with no major incidents.

The Empire Landmark Hotel opened in 1973 as the Sheraton Landmark, with the revolving Cloud 9 combining fine dining with panoramic views of the city and harbour. Towering 128 m (420 ft) over Robson Street and extending three levels underground, the hotel and restaurant became a popular destination for more than 30 years until it closed in September 2017. Extensive retrofitting costs and growing demand for residential space convinced the owners to demolish the building and replace it with a pair of towers featuring luxury apartments, retail space and offices.

Monumental project

With 20 years of multi-storey demolition experience and more than 250 employees throughout Canada, JMX and its engineers prepared to tackle this monumental project. In addition to the building’s size and the massive amounts of debris demolition would create, it needed to address the high-traffic location and potential for substantial safety risks.

“The Landmark demolition presented us with an inherently complex and challenging job,” said Shane Macpherson, director of business and projects for JMX West.

“In addition to the usual risks associated with standard high-rise demolition, we were presented with the unique round restaurant structure at the top of the tower. We also had to ensure zero risk to the large volume of vehicles and people going about their daily lives more than 400 feet immediately below us.”

JMX’s primary focus was mitigating dust and noise disruption, which led the company to look to robotic demolition. Previously, JMX used this “silent demolition” method with great success, taking down a 24-storey building in Calgary using two Brokk 400D remote-controlled demolition machines with Darda CC700 concrete crushers and SB552 hammers.

“People have this idea, when they hear a building is being demolished, that it’s going to be this big explosion,” Shane said.

“Demolition is inherently loud and dusty in their minds.

“And, historically, they’re right. But with today’s technology, it doesn’t have to be. We developed a plan that virtually eliminated dust and only registered 85 dB inside the demolition zone and 70 dB outside the hoarding. That’s six dB quieter than ambient street traffic.”

Reducing noise

JMX partnered with Brokk’s Washington state-based service fleet to help determine the right equipment for the job. JMX commissioned two Brokk 400 Diesel machines with CC700 crushers and SB552 hammers to work with a Brokk 160 electric unit and a CC420 crusher that it already owned.

As well as reducing noise, the Brokk machines’ power to weight ratio addressed the building’s robust construction and floor load limits. The 6 t Brokk 400D offered hitting power on par with a 9 to 12 t excavator in a

1.5 x 4.2 m (5 x 14 ft) footprint. It was also versatile – handling the 1,898 j energy class SB552 or the CC700 attachment with 376,917 j

of crushing force – allowing JMX to limit the need for additional equipment on the demolition floor.

“There are many ways to take down a building,” Shane explained.

“Using tower cranes and cutting the building apart is still the traditional method. However, it is costly and presents additional risks and challenges. To minimise the impact on the community, we felt top-down robotic demolition was the right choice and Brokk was the right partner. From equipment needs to trouble shooting, their team supported us throughout the entire process.”

Phase one started in November 2017 with JMX crews stripping the entire building to bare concrete. During this phase, 571,526 kg (1.26 million lb) of hazardous materials were removed from the site as well as 800 t of wood, steel and other materials.

As work progressed inside the building, JMX installed mast climbers around the perimeter of the Landmark’s concrete tower. These served to move personnel, materials, the three Brokk machines, two material handling skid steers and other equipment to the top of the building. Once the equipment was moved, JMX converted the mast climbers into a hoarding system that safely enclosed the entire work area to trap dust, debris and noise.

Shane Macpherson: “From the start, noise was one of our biggest concerns. But with the Brokk machines and crushing attachments, the actual demolition was incredibly quiet. You could be standing next to the operator, having a normal conversation.”

Crash decks

With preparations in place, JMX faced the most challenging aspect of the demolition, the Cloud 9 restaurant which extended out 3.7 m (12 ft) from the tower.

JMX engineered crash decks to support the restaurant’s floor and roof. Using the mast climbers, crews moved 72,575 kg (160,000 lb) of engineered steel and an additional 13,610 kg (30,000 lb) of scaffolding materials to the 41st floor to install these structures, which also included a double layer of plywood and net hoarding to contain material, dust and water.

The Brokk operators directed the remote-controlled machines to work their way through the restaurant.

Standing 5 m (18 ft) away, safe from debris and dust, operators were able to use the Brokk robots’ reach of 6.7 m (22 ft) vertically and

7.3 m (24 ft) horizontally to crush concrete slabs, beams, walls and columns.

The demolition area was essentially hidden from the ground and neighbouring buildings.

After Cloud 9 was removed, the machines continued the demolition, completing one floor every three to four days. With each new floor, the mast climbers were lowered and tied into the tower to continue the demolition process. The Brokk machines and skid steers moved down the stairwell using a specially engineered ramp. JMX installed five floors of shores under the active demolition floor. Using this method, it removed 38 storeys of the Empire Landmark’s tower in just nine months.

Crews used a high-reach excavator with a large concrete pulveriser attachment and three support excavators with specialised material processing attachments to remove the remaining two floors and other parts of the building – including multi-story podiums on either side of the tower, the tower core and three levels of the below-grade parking structure. Demolition concluded in August 2019. During the project, JMX crushed 40,000 t of concrete to recycle as road base and removed 630 t of asbestos containing materials.

• · First published in D&Ri, September-October 2019