Ontario Line station construction has started in the southern part of the project’s route, with teams preparing the sites for safe excavation and tunnelling. That’s where piling work comes in.  

Piling is a key first step in safely stabilizing the ground for excavation and for creating a water-tight perimeter that will house the underground station.

This important step has already begun at the future Queen-Spadina, King-Bathurst and Moss Park station sites. With plans to start piling at Exhibition, Osgoode and Corktown this spring and summer, major station construction in the southern part of the line is gaining momentum.

The Ontario Line is a brand-new subway line being built in Toronto and is one of the ways Metrolinx improving and building transit to reduce congestion across the region. The subway is expected see nearly 400,000 daily boardings and is projected to reduce major crowding at transit hubs Union Station and Bloor-Yonge by up to 14 and 22 per cent, respectively.

Read on for a closer look at what happens during piling work, what communities can expect and what’s up next through the downtown core. 

How does piling work?

Piling isn’t a new construction method; in fact, it’s been used for centuries. And while the materials used may have advanced significantly, the method, steps, and results are largely the same.  

Before station excavation starts, piles – which are reinforced concrete columns -- are drilled into the ground and connected to each other to form walls that provide solid structural support that is resistant to water leaks. To install the pile walls, a drilling machine creates holes between 10 metres and 14 metres deep and one metre in diameter around the perimeter of the future station site.  

A drilling rig then installs casings (hollow tubes) by rotating them into the holes, section by section. Excavated material is then removed from the casing using an auger. 

After this, reinforcements are added using a crane and concrete is poured into the holes to create solid structures.  

Next steps for construction 

Once the piles are installed at a given site, excavation work begins to dig out the underground station caverns, removing earth, soil and rock.  

This sets the stage for future tunnel boring machines to pass through the caverns, connecting all the underground stations. 

In total, approximately 3,000 piles totalling 45 km in length will be installed for the six underground stations in downtown Toronto – King-Bathurst, Queen-Spadina, Osgoode, Queen, Moss Park and Corktown.  

What to expect 

While piling is vitally important for safe station construction, it does result in some noise due to the heavy machinery that is needed to carry out this major work.  

Equipment used during piling construction includes drill rig machines, cranes, excavators, and concrete pumps. Concrete trucks are also often on site.  

To reduce impacts to residents and businesses in the areas we’re working, work will happen primarily during daytime hours. We will also be installing noise and vibration monitoring equipment so we can track our levels and adjust where needed and possible.  

The Ontario Line isn’t the only project where piling work is happening. Piling is going on across many important projects, as we build and improve transit across the region.

We’re here for you

 We know building transit can be disruptive, but we’ll be here for you every step of the way. Where there is concern, we'll listen. Where there is opportunity to improve, we'll act.

We’ll keep communities informed through the construction process through neighbourhood canvassing, open houses and virtual information sessions where residents can receive updates, provide feedback and ask questions.

Additionally, we host construction liaison committee meetings where we collaborate with businesses on creative solutions to address impacts.

Our priority is to always communicate about construction activities ahead of time through our online construction notices. Notices for upcoming and ongoing work can be found on our construction notices website.

Any questions or concerns related to Metrolinx work in the community can be address via our community engagement team. They can be reached by email during business hours ontarioline@metrolinx.com or through the 24/7 hotline 416-202-5100.