blossoms on a tree

How the Yonge North Subway Extension will be seen, but not heard

Metrolinx considers new technology and solutions to keep neighbourhoods quiet during construction.

Apr 28, 2021

Building a major transit route, including Toronto’s Yonge North Subway Extension, means lots of moving pieces.

And that can lead to questions from those working and living nearby on how noise and vibration concerns will be handled.

Experts on the project have some very clear answers.

The Yonge North Subway Extension will transform the way people move around York Region and travel to and from downtown Toronto. The project will reduce commute times by up to 22 minutes and bring the subway closer to the people who will live in the centre of vibrant new communities in heart of York Region in the coming years, curbing traffic congestion as those burgeoning neighbourhoods grow.

As Metrolinx brings big transit benefits to communities in York Region and Toronto that will be impossible to ignore, there’s a strong focus on how to design and build a subway the neighbours barely notice.

blossoms on a tree

Metrolinx is using innovative techniques and renowned experts to figure out the best way to handle noise and vibration along the Yonge North Subway Extension. And to point out how great and sensitive local neighbourhoods are, here are some blossoms along Richmond Hill Street. (Metrolinx photo)

Deep Work

One important factor that will help the extension keep a low profile is the underground tunnels below residential areas are proposed to be built at a depth where there would be no direct impact on the homes above using the latest, state-of-the-art tunnel boring machines that will carefully eat their way through soil and rock. The exact details of the depth will be determined through further study, but early plans suggest the bottom of the tunnels – where trains create noise and vibration as they pass over the tracks – will be at least 20m. below the surface through the section of the route that leaves Yonge Street. That’s roughly as deep as a six-storey building is tall.

A big benefit to the new tunnels is that they’ll be based on modern and up-to-date industry standards, which have significantly improved since the first subway lines in the GTA were built many decades ago. They’ll be surrounded by thick reinforced concrete and will be built to strict design and engineering standards. This proven technology will ensure future subway services won’t be a disruption for the community.

Long before the first shovelful of soil is turned to start construction, Metrolinx does its homework. A complete picture of the potential effects the project might have over its lifetime will be captured through what’s called an environmental assessment – often referred to as an EA. This thorough study will investigate everything from what particles are in the air, to what the layers of the earth beneath the surface are made of – and how any of those conditions might change with the addition of the new subway service that’s planned.

The EA would not be complete without insight from the people who live, work, and play in the communities the extension will serve. Metrolinx will reach out to collect their feedback and ideas through events like online public open houses and, when it’s safe to do so, in-person events. The input and data Metrolinx gathers will help project planners make sure all the necessary noise and vibration solutions are put in place to keep things as quiet and peaceful as possible in each neighbourhood so they stay sought-after places to live in.

Proven Measures

Metrolinx is looking at a wide array of proven noise and vibration solutions for the project, including high-grade rail fasteners that keep all the track parts tightly together and ballast mats to help cushion the tracks and reduce vibration.  Rail dampers can also be used to help reduce the noise from passing trains. The iconic clickity-clack sound of train wheels passing over the uneven spots where two sections of rail join together won’t be made by the Yonge North Subway Extension because modern subway rails are welded seamlessly together to provide a smooth and quiet ride.

Another option open to Metrolinx designers is one the TTC was first to use in North America. The latest evolution of this ingenious idea would float the track above the bottom of the tunnel. The rails would be attached to large concrete slabs that are cushioned by thick rubber pads that look like oversized hockey pucks. These disc-shaped pads soak up the vibration from passing trains.

On the surface sections of the line, noise walls could be used in certain areas to block and absorb sounds. These walls can be designed with a combination of solid and transparent panels, and have been installed across many parts of the Metrolinx rail network.

Metrolinx strives to go above and beyond provincial regulations that put limits on the noise and vibration that come from the construction of new transit projects. Metrolinx will monitor noise and vibration levels and schedule noisier work when it makes the most sense. Special noise-muffling equipment and state-of-the-art machinery are also available to help keep the noise down during construction.

The goal is to ensure after the extension opens, there is no significant difference in noise and vibration levels compared to today. More specific details will be available from Metrolinx in the coming months about the exact solutions that will be used on the Yonge North Subway Extension, after the EA has been completed and residents have had a chance to provide their input.

by James Moore Metrolinx communications senior advisor