Big digs: 7 major tunnel projects underneath your feet

Learn more about the epic engineering that goes into underground work.

Crews work below the streets of Vancouver for the Broadway Subway project. – Broadway Subway Project Corporation

It’s a childhood memory almost everyone shares. Taking a shovel somewhere in the woods and seeing how deep you can dig.

These teams are digging on a whole other level with their massive tunneling projects. When you can’t go over or around, sometimes your best option is to go underground. Tunnels are critical for a wide range of infrastructure, including roads, water treatment, power generation, transit and much more.

The George Massey Tunnel Replacement

Originally planned to be a bridge, this replacement for the aging George Massey Tunnel has been a long time coming. After spending years of studies and political disagreements, the $4.15B project now has three short-listed bid teams. The project involves building a new toll-free, eight-lane tunnel along Highway 99 between Richmond and Delta. The winning team is expected to be chosen next spring.

Broadway Subway

Broadway Subway

Big things are happening underneath the streets of Vancouver. The Broadway Subway Project is a 5.7 km extension of the Millennium Line, from VCC-Clark Station to Broadway and Arbutus. 700 metres will be elevated, extending from VCC-Clark Station to a tunnel portal near Great Northern Way. Five kilometres will be tunneled below the Broadway Corridor. The tunneling is being done by two boring machines, named Phyllis and Elsie. Just this month, Phyllis broke through to the fourth of six underground stations planned. But don’t fret. Phyllis won’t be lonely long. Elsie is expected to reach the same point later this fall. The new line is scheduled to open in 2026.

Burnaby Mountain Tunnel

Trans Mountain

What’s the quickest way to get past a mountain? You go right through it. As part of the Trans Mountain Expansion Project, crews will use a tunnel to connect Burnaby Terminal and Westridge Marine Terminal. The team says this avoids impacts on residents and existing infrastructure. Trans Mountain’s contractor, Kiewit Ledcor TMEP Partnership (KLTP) will used a tunnel-boring machine to construct the 2.6-km tunnel through Burnaby Mountain. Drilling wrapped up last September after 225 mining days with 20 hours of mining per day.

Louis-Hippolyte-La Fontaine Tunnel repairs

Quebec Transport Ministry Archives

Sometimes an old tunnel just needs a bit of sprucing up. Quebec officials are hoping $2.5 billion in repairs will keep the Louis-Hippolyte-La Fontaine tunnel, which connects the island of Montreal to the South Shore, in service for the next 40 years. The main interventions in the tunnel consist of major structural rehabilitation, upgrading operating equipment, redesign of service corridors and adding fire protection. Crews are currently repair the tunnel’s tube structure and carrying out the reconstruction of concrete slabs on Autoroute 25. Work is expected to wrap in 2026. The tunnel opened to traffic in 1967.

Hydro One Tunnel

This year Hydro One, Ontario’s largest electricity transmission and distribution service provider, launched construction on a new tunnel that will run 85ft below ground in downtown Toronto, from the Esplanade to Bay and Dundas. The tunnel will be 12ft in diameter, approximately the size of three park benches, and will house new transmission cables, replacing cables that have served Toronto’s downtown core since the 1950s. Hydro One is investing approximately $120 million dollars in the infrastructure renewal project.

Twin SEM Tunnels Project

What’s cooler than digging one tunnel? Digging two tunnels, of course. But it wasn’t easy. Toronto’s Highway 401/409 Twin SEM Tunnels Project involved construction two rail tunnels under 21 active lanes of highway traffic, alongside the existing active rail corridor, and had to be completed with zero impacts to either active transportation system. The complex project, expanding the Kitchener GO corridor as part of Metrolinx’s Regional Express Rail program, was developed by Toronto Transit Partners, a consortium consisting of EllisDon, STRABAG, WSP, Dr. G. Sauer & Partners, and Jensen Hughes. Their efforts did not go unnoticed. The team was awarded the the 2022 Project of the Year over $100 million by the Tunnelling Association of Canada (TAC). 

Ashbridges Bay Treatment Plant Outfall


The largest subaqueous (a fancy way of saying “underwater”) tunnel to be built in Toronto, the Ashbridges Bay project is already turning heads. It won Tunneling Project of the Year from the TAC, the 2021 and 2023 TAC Canadian Innovation Initiative Award, and Bentley’s Year in Infrastructure 2020 Awards for digital delivery advancements. The new outfall is expected meet peak design flows under highest recorded lake water level conditions while achieving regulatory standards. It will be one of the largest outfalls constructed in North America and is designed to significantly improve water quality along Toronto shorelines and contribute to improve the overall environment of the region.


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