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Aecon’s expertise helps keep Canadians on the move for over a century

Twin tunnels under Toronto the latest in a long string of high-profile infrastructure projects

One of four tunnel boring machines at the west launch site. The same type of boring machines will be used for the east tunnels. (Photos courtesy of Metrolinx.)
One of four tunnel boring machines at the west launch site. The same type of boring machines will be used for the east tunnels. (Photos courtesy of Metrolinx.)

Deep beneath the streets of Toronto, two tunnels are taking shape — tunnels that will, when completed, replace thousands of vehicles as the preferred route for commuters moving across Canada’s largest metropolitan area.

When a major infrastructure project of this magnitude is undertaken, the choice of contractor is a very important part of the process — only the best need apply. In the case of the Eglinton Crosstown Light Rail Transit (LRT) project being constructed for Metrolinx, the Province of Ontario’s regional transportation agency for the Greater Toronto and Hamilton Area, one of the companies which fit the bill is one of Canada’s largest contractors. 

With headquarters in Toronto and Calgary, AECON has been building major infrastructure projects across Canada since its founding in the 1870s. The company started out in above-ground work, and has been involved in many landmark structures over the years. In many cases these projects assisted in expanding transportation networks, allowing more people to move more efficiently. From constructing the St. John’s harbour in Newfoundland to ferry terminals in Vancouver to the St. Lawrence Seaway, AECON infrastructure projects have been integral parts of building Canada’s largest cities. It has also been part of building many of the country’s recognizable structures such as the CN Tower.

Over time, the company has expanded into a variety of industries, with divisions focusing on mining and energy operations as well as infrastructure. Transportation and large government and institutional projects have remained a key part of AECON’s operations, including tunnelling activities.

Expertise in tunnelling will certainly help with the challenging Metrolinx project the company successfully bid on in 2013. The Eglinton Crosstown LRT represents a $177 million project for the joint venture with ACS Dragados Canada Inc. Leading the JV, AECON will oversee the boring of two 6.5-metre tunnels starting at the eastern end of the more than 10-kilometre underground segment. The construction will run 3.2 kilometres to where it will meet two tunnels being bored from the west at Yonge Street.

“The main feature of the contract is two parallel tunnels that run under Eglinton Avenue, that will carry a light rapid transit line — that is a train that draws power not from a third rail but from a catenary above it, and runs both below and above ground” said Marco Giorelli, AECON project manager. “The tunnels will be cut by two state of the art tunnel boring machines.”

A rendering of the west launch shaft. The east launch shaft will look similar.

Two earth pressure balance (EPB) Tunnel Boring Machines (TBMs) will do the work of boring through the alluvial soil, sands and silt beneath Toronto. In the case of the Eglinton Crosstown LRT, Metrolinx has purchased the machines itself and is providing them to the contractors. That’s unusual for similar projects, Giorelli said.

“The TBMs have been purchased by the project owner and given to the contractors to use, for both us on the east side and the contractor on the west,” he said. “Not only are they providing the TBMs to the contractors, but they are also providing the concrete segmented tunnel liner.”

With procurement of a TBM often taking more than a year, having Metrolinx handle that aspect of the contract will mean a quicker completion time for the overall project.

EPB machines were selected for the job because of the geology of the area.

“When you bore a tunnel in rock, the difficulty is to cut the rock. But when you bore soft ground the excavation itself is relatively easy — the real challenge is to support the excavation,” Giorelli said. “Because we’re under some major avenues in Toronto with buildings on both sides of the street, we have to ensure we don’t have any volume loss, which can cause settlement.”

Continuous geotechnical monitoring is conducted to ensure the work is not causing surface disturbances, he added.

AECON has just started the first stages of the construction — finding and relocating the services to allow construction of the entry point for the two TBMs. In an urban area, that can be a challenge, Giorelli noted.

“We are in an urban environment — we need to find and relocate the utilities, and once they are out of the way we can build the shaft. Once the launching shaft is complete, we can bring in the TBMs and start boring,” he said. “We will start to drive tunnels in the fall.”

At the end of the contract, AECON will be handing over the two tunnels, along with emergency exit shafts and similar smaller structures, to Metrolinx. The Eglinton Crosstown LRT is expected to enter service in 2020.

A rendering of what the twin tunnels look like underground.

Two earth pressure balance (EPB) Tunnel Boring Machines (TBMs) will do the work of boring through the alluvial soil, sands and silt beneath Toronto. In the case of the Eglinton Crosstown LRT, Metrolinx has purchased the machines itself and is providing them to the contractors. That’s unusual for similar projects, Giorelli said.

“The TBMs have been purchased by the project owner and given to the contractors to use, for both us on the east side and the contractor on the west,” he said. “Not only are they providing the TBMs to the contractors, but they are also providing the concrete segmented tunnel liner.”

With procurement of a TBM often taking more than a year, having Metrolinx handle that aspect of the contract will mean a quicker completion time for the overall project.

EPB machines were selected for the job because of the geology of the area.

“When you bore a tunnel in rock, the difficulty is to cut the rock. But when you bore soft ground the excavation itself is relatively easy — the real challenge is to support the excavation,” Giorelli said. “Because we’re under some major avenues in Toronto with buildings on both sides of the street, we have to ensure we don’t have any volume loss, which can cause settlement.”

Continuous geotechnical monitoring is conducted to ensure the work is not causing surface disturbances, he added.

AECON has just started the first stages of the construction — finding and relocating the services to allow construction of the entry point for the two TBMs. In an urban area, that can be a challenge, Giorelli noted.

“We are in an urban environment — we need to find and relocate the utilities, and once they are out of the way we can build the shaft. Once the launching shaft is complete, we can bring in the TBMs and start boring,” he said. “We will start to drive tunnels in the fall.”

At the end of the contract, AECON will be handing over the two tunnels, along with emergency exit shafts and similar smaller structures, to Metrolinx. The Eglinton Crosstown LRT is expected to enter service in 2020.

Company info

555 South Flower St.
Suite 3700
Los Angeles, CA
US, 90071-2300

Website:
aecom.com

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