Stop Buying TBMs Like They’re Disposable

November 12, 2025 · 4 min read

Tunnel Boring Machines, TBMs, might be some of the most interesting pieces of engineering on Earth. These self-contained moving factories carve the tunnels that become our subways, sewers, and utilities, while minimizing disruption to the world above. Each one is a marvel of precision and power, custom-built for the soil, diameter, and geology it must face. Such sophistication comes at a price; TBMs can cost hundreds of millions of dollars to design, build, and operate.

Take, for instance, Montreal’s Blue Line extension. In 2024, the tunneling contract for its eight-kilometer segment was awarded for 1.1 billion dollars, a price that reflects not only the complexity of urban tunneling, but also the one-off nature of how we approach it. Yes, Montreal’s soil makes tunnelling more complicated, but this isn’t a one-off situation. As it stands, when a project wraps up, those massive machines suddenly have nowhere to go.

It doesn’t have to be this way. There’s an active international market for used TBMs. They are routinely refurbished and redeployed, and studies have shown that reused machines can meet modern performance standards while saving both time and money. Instead of exporting our machines, and the lessons that came with them, what if we re-used and re-invested both at home?

That single-use mindset doesn’t just waste machines; it wastes momentum.

The Momentum We Keep Losing

Every major Canadian transit project seems to introduce its own “revolutionary” tunneling method. In Toronto alone, we’ve seen massive single-bore tunneling on the Scarborough Subway Extension, twin-bore setups on the Eglinton Crosstown projects, and even hybrid configurations for the Ontario Line, each using different machines, diameters, and technical standards.

The reasoning is straightforward, but short-sighted. Each project is optimized for its own conditions, different dynamic envelopes for the rolling stock, station geometries, and specific technical or ventilation needs. Customization also mitigates over-excavation risk, which can add cost and complexity to the fit-out once dug. On paper, smaller or tightly tailored tunnels can look cheaper, if you think in a project mindset.

The hidden cost is momentum. Every time a project starts from zero, we pay again for design, procurement, learning curves, and teams. Expertise gained by one project dissipates because there is no pipeline to keep specialists employed; they simply move on. Equipment that could have served another city is sold off or scrapped. We behave as if each new project were our first. In Europe and Asia, this is how tunneling is done. Countries like Japan and Norway maintain continuous tunneling programs that treat TBMs as long-term strategic assets rather than temporary tools.

The worst mistake we can make is to stop tunneling.

From Projects to Programs: Building Continuity

This piece isn’t about TBMs: they are a mirror of how we plan projects in the broader sense.

Whenever we start a project, we fixate on getting it delivered, and forget to plan what comes next. In Ottawa, Stage 2 LRT is expected to conclude in 2026-2027, yet Stage 3, the logical continuation, remains unprocured. We know we want to build it sooner than later, why do we risk losing the expertise and momentum before continuing? It is not a problem in Ottawa alone, we see it with a wide variety of projects because we think in funding cycles. What if we thought in continuity instead? Even in Toronto, with Metrolinx responsible for the planning and delivery of most active projects, the sequencing for future ones remains wishful thinking more than actual planning.

Like a TBM, our project capacity needs a continuous stream of work to valorize the experience and efficiency we gain. Across the country, our infrastructure programs rise and fall with funding cycles, political windows, and procurement resets.

Program thinking is the antidote. It treats infrastructure not as a series of one-time events, but as a continuous practice. Instead of chasing “the next big project,” it focuses on sequencing; ensuring there is always a next step ready when one finishes. The goal isn’t to standardize everything into sameness, but to build a shared foundation of tools, contracts, and design assumptions that make delivery faster, safer, and smarter over time.

Like a TBM, our capacity to build only stays sharp if it keeps turning. The more we stop, the more we forget how to move forward. The same inertia that sidelines a TBM after one job is the same inertia that sidelines our institutions between them.

Building Capacity, Not Just Projects

Canada has the talent, the tools, and the ambition to deliver world-class infrastructure, but we still act like each project is exceptional and exists in a vacuum. We design, build, and move-on, instead of retaining and refining. We call it innovation, but what we’re really doing is resetting. In the same way the Major Project Office can help reshape how Canada delivers national infrastructure, we need to think beyond the project and start designing for continuity.

Infrastructure is not a series of one-off achievements; it’s a continuum of capability. The same logic that would keep a TBM in service, standardization, long-term planning, and regional coordination, could make every aspect of public building more resilient.

The real challenge isn’t technical. It’s cultural. We need to move from projects that end to systems that endure. Because the infrastructure that truly serves people isn’t the one that breaks ground: it’s the one that keeps building capacity to do it again.