TAKING THE LONG VIEW
The Société de transport de Montréal is Building An underground train garage so it will Be able to increase service on the métro’s orange Line. After touring the construction site on tuesday, René Bruemmer has details of the $439-million project.
For the first time in over a decade, Montreal is adding an underground train garage to its métro system to increase service on its overcrowded Orange Line.
On Tuesday morning, the Société de transport de Montréal gave a tour of the facility and tunnels located 30 metres underground. The process involves tunnelling 650 metres to connect the future garage to the Côte-Vertu métro station, which is at the northern terminus of the western end of the Orange Line. It is similar to the process of constructing any métro tunnel — slowly and laboriously carving through the thick rock that lies far beneath the city ’s streets, homes and parks.
WHY?
The Orange Line reached capacity in 2011, and has since surpassed it, STM officials noted. About 35 to 36 trains run on the line every day, getting to stations every two minutes and 30 seconds during rush hour. By building an underground garage that can house 10 additional train cars that will run at rush hours, they can increase service to every two minutes, a 25 per cent boost in capacity. CôteVertu station already has a garage that holds 10 trains. Another 20 can be housed at the HenriBourassa station garage, and five at Montmorency.
The extension of the métro Blue Line, scheduled for 2026, will bring more passengers to the Orange Line.
The garage will also have a service bay where mechanics can repair and maintain the trains, via a trench dug beneath the tracks.
A GARAGE IN THE BOWELS OF THE EARTH
The construction site takes up a whole city block in St-Laurent, on Marcel-Laurin Blvd. next to the Bombardier Aerospace plant. At a depth of 30 metres, roughly the equivalent of a 10-storey building, a tunnel running 650 metres northwest from the Côte-Vertu métro station will connect to a switching area at the same depth, where the trains can be moved: two tunnels will extend about 600 metres each and can hold four trains — each métro train is 150 metres long. Additional trains can be housed in the access tunnel. A third, shorter tunnel will be used as the service garage.
A maintenance building, occupying seven storeys underground and three storeys above, will allow employees access to the garage and provide workspace.
HOW DO THEY DIG IT?
Excavators came in first to shovel out the dirt, to a depth of roughly seven to 10 metres, until they hit bedrock. Dynamite was used to break up the rock to make way for the vertical underground structures like the building, and an entrance road down to the tunnel.
To carve the tunnel, a machine called a roadheader, which weighs 135 tonnes and was imported in pieces from Germany, is used. It has a circular grinder embedded with dozens of steel, cone-shaped spikes that rotate at high speed. The spinning mace is at the end of a boom that swings side to side and up and down, bashing out rock at a rate of three to five metres a day. Every day, 30 to 40 large dump truck loads are excavated. The teeth on the mace have to be replaced every two hours. GPS systems in the roadheader ensure the tunnel is going the right way.
To shore up the tunnel walls and keep them from collapsing, a “jumbo drill” hammers in steel rods up to four metres long to anchor the rock. Concrete is sprayed on the walls six inches deep to keep rock from falling.
Air is pumped into the tunnels via massive ventilation tubes. If there is a malfunction, workers carry mini scuba-tank like devices that can provide air for 60 minutes. Media were advised to stay calm to preserve air while using the mini scuba tanks if a problem arose. This seemed unlikely.
In the winter, the tunnels stay relatively warm that far underground. Water drips from the ceilings of rock that have not yet been covered in concrete.
COST AND TIMELINE
Work on the garage started a year ago and is projected to last another three years. The total cost of the project is $439 million. In total, 320 workers are employed at the site, working seven days a week. The Côte-Vertu station will have to be closed for about three months — from June to August 2020 — to complete the work. In total, 1.5 kilometres of tunnels will be dug.
Two tunnels northward, 50 metres long, are being started, in case the Orange Line is ever extended toward, or perhaps even into, Laval, to join with its other end at Montmorency and complete the circle.