Arriving passengers at Montréal-Pierre Elliott Trudeau International Airport may be confused when stepping out to reach the parking garage across from the arrivals area, confronted with a giant excavation and construction crane, and the temporary elimination of some of the garage’s previous access points.
It’s all part of a late decision to locate one of 26 stations at the busy air transportation hub, which had been threatened by a loss of passenger traffic during the COVID-19 pandemic.
Construction began almost a year ago on what will be the new light rail 67-kilometre Réseau express métropolitain (REM)’s second deepest station (after Édouard-Montpetit), 35 metres or more than 10 storeys below grade, sandwiched between the terminal and multi-level parking structure. It will be the last of the $7 billion REM stations, opening in 2027.
The excavation is a challenge because of its sensitive airport location and the groundwater awash below the surface.
Connect Cité, a general partnership between Aecon and EBC in which Aecon is the lead partner, finalized the $219 million contract with ADM Aéroports de Montréal to build the station. This is only the civil component of a station estimated to cost as much as $600 million.
The partnership must complete its work by spring 2026 with the station then attached to the connecting REM tunnel. This is one of the few portions of the REM running underground with the work carried out by REM general contractor Nouvlr.
Once complete, the automated transit line will shuttle passengers 25 minutes to and from downtown Montreal.
Excavation of the below surface rock in the narrow trench is almost half complete after that portion of the project began last October. Altogether 104,000 cubic metres of rock – the equivalent of 42 Olympic-size swimming pools – are being extracted.
The excavation is being carried out by hydraulic rock splitters and a road header. Explosives were ruled out because of the “impact on airport operations when setting up a security perimeter for each blast” and the concurrent vibrations generated, said Aecon project director Stéphane Pereira Leonardo.
The excavation is carried out in a series of layers.
For each layer, a continuous row of holes is drilled throughout the surface of the trench about one metre apart.
The splitters are then inserted to a depth of 1.5 metres.
“We can excavate up to two layers, with a maximum of three metres of non-consolidated face,” Pereira Leonardo said.
Rock consolidation is carried out with rock anchor bolts (46 millimetres wide and eight metres long) and a layer of shotcrete reinforced with synthetic fibres of 75 millimetres in length.
Once the bottom has been reached structural work will begin on the building with installation of a waterproof membrane and laying concrete before starting construction on the walls.
Final work will be the station finishes including masonry, electro-mechanical and architectural as well as the installation of 10 high speed elevators.
Besides the proximity of the airport terminal and garage (one-and-a-half metres from the arrivals or drop off area and five metres from the garage), the other challenge has been water. The interface between the rock and the till found water running at 12 litres per second.
Water has therefore been pumped from the excavation.
“We made a gutter on the upper part of the rock bench to channel the water to two collection points” and then to a purpose-built onsite treatment station, Pereira Leonardo said.
The project is definitely a feather in the cap for the contractor.
“We are honoured to be working with ADM and our partner to deliver this world-class project,” Roger Arsenault, vice-president for Aecon Eastern Canada, said. “This project further strengthens Aecon’s presence in Québec.”
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