A range of tunnel projects have been advancing across Canada in recent months, including in Vancouver, Montréal, Toronto and Darlington. In Vancouver, the main civils works for the Second Narrows Water Tunnel project has reached substantial completion.
Whereas in Montréal, for the Blue Line Extension project, preparations for main tunnelling are advancing with transport of the TBM to site. Assembly of the shield is underway for launch in 2026.
Also in preparation is tunnelling for cooling water tunnel at a new nuclear power project in Darlington, Ontario. The TBM to bore the tunnel has arrived on site. Also in Ontario, construction preparations continue, in Toronto for the Ontario Line.
With so much achieved on underground projects over many decades, the Tunnelling Association of Canada (TAC) has launched a pilot mentorship program for experienced engineers to help younger tunnelers.
VANCOUVER – WATER TUNNEL
The Traylor Bros and Aecon joint venture working on Vancouver’s Second Narrows Water Supply Tunnel has reached substantial completion on construction. The new Metro Vancouver water supply tunnel is 6.5m in diameter, just over 1km long, and contains three new large-diameter steel water mains. The mains are designed to withstand a one-in-10,000- year earthquake and deliver more than one million litres of drinking water a day to Vancouver, Burnaby, Richmond, New Westminster, Delta, and parts of Coquitlam and Surrey.
The tunnel lies 30m below the bottom of the Burrard Inlet, east of the Ironworkers Memorial Bridge, between Burnaby and the District of North Vancouver.
It was excavated through a variety of ground conditions using a slurry TBM, and replaces three water mains built between the 1940s and 1970s that are vulnerable to seismic damage.
“Building this tunnel under the Burrard Inlet was a massive project and is another great example of the critical infrastructure that Metro Vancouver delivers for this region,” said Mike Hurley, Chair of Metro Vancouver’s board of directors.
“For a sense of scale, this tunnel was large enough to drive a truck through – and now it holds three separate water mains that will increase capacity and ensure we can continue supplying water following a major earthquake.”
With the tunnel now substantially complete, Metro Vancouver will start connecting the new water mains to the existing water supply system. Work on these tie-ins will occur on both sides of the Burrard Inlet, and each connection is expected to take several months to complete.
The Second Narrows Water Supply Tunnel is expected to be fully in service by 2028.
In 2024, the project won TAC’s Canadian Project of the Year Award. This year, it received the Award of Excellence from the Association of Consulting Engineers – BC Chapter in the Municipal and Civil Infrastructure category.
TORONTO METRO, DARLINGTON NUCLEAR
Among key tunnel projects underway in Ontario are the expansion of Toronto’s metro with the Ontario Line, and preparing for boring of a cooling water tunnel for a new power plant at Darlington nuclear site.
Getting down in Toronto
Ground breaking has taken place on the second tunnel launch shaft for Toronto’s Ontario Line.
From the launch shaft, TBMs will travel north, digging 3km of twin tunnels underneath Pape Avenue. The launch shaft will eventually serve as the tunnel portal, where Ontario Line trains will move from above-ground tracks to the underground tunnels.
The 15.6km-long Ontario Line will have 15 stations, running from Exhibition Place through the downtown core and connecting to the Line 5 Eglinton at Don Mills Road.
Gerrard station, located just south of the launch shaft and future portal, will put nearly 12,000 people within walking distance of the Ontario Line, with over 3,000 passengers expected to use the station during the daily rush hour. Work on the first launch shaft near Exhibition station started in November 2024.
In mid-2025, Metrolinx launched a naming competition for the first pair of the four TBMs that are to be deployed on the project.
Boring for nuclear power project
Ontario Power Generation (OPG) is partnering with GE Hitachi Nuclear Energy, SNC-Lavalin, and Aecon on the project to build Canada’s first small modular reactor (SMR), located at the Darlington nuclear site. The project calls for construction of a 3.4km-long condenser cooling water tunnel, which will be constructed by a 6.97m-diameter Herrenknecht TBM – which recently arrived in Ontario. The TBM ‘Harriet Brooks’, named after Canada’s first nuclear physicist, arrived at the Port of Oshawa and transported to the Darlington nuclear site in 15 lorry loads. Assembly on site is to be performed in early 2026.
The Government of Ontario is working with (OPG) on the Can$20.9 billion (US$15.2 billion) project, which will deliver four grid-scale SMRs. The first facility, which will also be North America’s first commercial, grid-scale SMR, is planned to be operational by 2030.
Construction work on the Darlington New Nuclear Project (DNNP) began in Q3-2022, with the installation of utilities, including fire lines, water lines, sanitary sewer lines, and network cabling. Construction on a few important buildings, including the on-site fabrication building, is also under way.
The four SMRs are designed to meet Ontario’s electricity demands, which are rising for the first time since 2005. The Independent Electricity System Operator has forecast that the province could need to more than double its electricity generation in less than 30 years.
Nuclear power currently provides about 50% of Ontario’s electricity supply.
“A fleet of SMRs at the Darlington New Nuclear Site is key to meeting growing electricity demands and net zero goals,” said Ken Hartwick, President and CEO of OPG.
“OPG has proven its large nuclear project expertise through the on-time, on budget Darlington Refurbishment project. By taking a similar approach to building a fleet of SMRs, we will deliver cost and schedule savings, and power 1.2 million homes from this site by the mid-2030s.”
MONTRÉAL – BLUE LINE METRO
The Blue Line Extension project is a key development project in the east end of Montréal. The 6km-long metro extension will add five stations east of Saint- Michel station, bringing the Blue Line into Anjou. The extension project is a collaboration between five partner organisations: the Ministère des Transports et de la Mobilité durable; the Autorité Régionale du Transport Métropolitain; the City of Montréal; the Société Québécoise des Infrastructures; and, the Société de Transport de Montréal. The TBM that will dig the metro’s Blue Line extension recently arrived in the city.
The 9.7m-diameter Herrenknecht machine –which will be the largest TBM ever used in the province of Quebec – is to build a 4.6km-long tunnel to Anjou, a first in the Montreal metro system.
The TBM is scheduled to be launched in Q2-2026. Components were transported from the Port of Montreal to the launch site, located at the future Vertières metro station. The shipments were undertaken in a series of mainly night-time operations. Key vertical excavations have been completed at both Vertières station and Madeleine-Parent station in preparation for the TBM assembly and launch. At Vertières, 74,000m3 of soil and rock were removed to build the 26m-deep shaft; at the future Madeleine-Parent station 63,000m3 of rock was excavated for construction of a 29m-deep shaft.
Excavation work is also planned or underway for the construction of seven auxiliary buildings, the future Anjou underground garage, and several operational infrastructures. This means that more than 15 major projects will be carried out simultaneously.
The stations on the Blue Line extension are scheduled to come into service in 2031.
“For the past year, work on the Blue Line extension has been moving forward on schedule, and tangible progress has been made,” said Maha Clour, head of the Blue Line Project Office.
“At the future Vertières station, horizontal excavation has already begun, with our teams now digging a portion of the tunnel eastward to accommodate the tunnel boring machine. Digging is also under way on the westbound tunnel toward Saint-Michel station.”
The Blue Line Project Office will invite the public to name the TBM.
TAC PILOTS MENTORSHIP PUSH
Earlier this year, the Tunnelling Association of Canada (TAC) launched a pilot mentorship program aimed at strengthening professional ties in the Canadian tunnelling community. Open to students, early-career professionals, and seasoned industry leaders, the initiative offers a structured platform for TAC members to connect, share knowledge, and support one another’s professional development.
The programme’s core goals include:
- enhancing member connections across the TAC network;
- providing accessible career guidance and support;
- promoting diversity and inclusion in the industry; and,
- cultivating a collaborative and supportive professional environment.
TAC says that the program is designed to support career development and should not be considered a source of technical training or mentorship. Participants are expected to benefit in different ways, TAC adds. Mentors would have opportunity to give back to the tunnelling community by sharing their experience and helping to shape the next generation of professionals; mentees can gain valuable career insight, expand their networks, and learn directly from seasoned experts. The initiative is being supported on PDL Mentoring, a platform that matches mentors and mentees based on shared interests and areas of expertise. This approach is to enable focused and personalised conversations.
The pilot phase of the mentorship initiative is to run for one year, during which TAC plans to evaluate participation, feedback, and overall impact of the program to determine how to take it forward.
