What if a level of government ruled out The Boring Company?

1. Why consider this scenario

One can imagine several triggers, none more likely than another and none worth singling out: a delay or a hitch on a Boring Company site elsewhere (Nashville, Las Vegas) that would cool a public decision-maker; a competitive-tender or Canadian-content rule that would rule out a single unsolicited supplier; a diplomatic, trade or security reservation, like those that sometimes affect technology exchanges with American companies; or simply the political caution of a government that prefers a long-established consortium to a company still young at this type of contract. The precise reason matters little for the analysis that follows — the financial calculation is the same whatever the cause.

It is also the most honest answer to a criticism that comes up often: "aren't you dangerously dependent on a single private company, run by a single person?" Rather than a reassuring slogan, here is what it would really cost to do without it — and the conclusion, spoiler, is that the project survives this scenario. It simply costs more.

2. The right diameter to bore

A tunnel-boring machine never delivers the usable diameter directly: you have to add the thickness of the segmental concrete lining installed behind the cutter head. To reach the 3.66 m interior already chosen on the Dimensions page — the measure that comfortably respects Vélo Québec's cycling-width standard — a conventional TBM must bore appreciably wider than that finished diameter.

The best point of comparison is a recent, Canadian site in a related rock: Ottawa's combined sewage storage tunnel (CSST). A Dragados-Tomlinson consortium bored two tunnels totalling 6.2 km with a 3.7 m diameter TBM, in limestone formations shot through with bedded black shale — an Ordovician geology of the same family as Québec's — to deliver a finished tunnel of about 3.0 m. The gap, about 350 mm, corresponds to the thickness of the lining.

In other words, aiming for a 3.66 m interior requires boring about 40% more cross-sectional area than at Ottawa — and far more than the 3.0 m bored in Montreal for the Rosemont reservoir tunnel, often cited as a benchmark but in reality too narrow once you account for the lining: that site housed a 2.1 m water main, not an open 3.66 m cycling space.

3. The going rate for a conventional TBM

Two real sites make it possible to estimate what a conventional TBM at the right diameter would cost today.

Both methods converge on a common range:

4. The impact on the full budget

The good news: this change of supplier touches only two lines of the budget. Everything else — stations, technical systems, escape shafts, bike fleet, land, annual operation — does not depend on who dug the hole.

• Low: close to the rescaled Rosemont benchmark — the most favourable assumption for a conventional supplier.
• Centre: average of the two benchmarks (Rosemont and Ottawa's CSST) — the default scenario to adopt.
• High: close to the rescaled CSST benchmark — the most cautious assumption, without the economies of scale of a supplier that mass-produces its TBMs.

5. Compared to other modes of transport

As on the Price comparison page, three ways to measure: per kilometre built, per trip, and per user each year.

The cost per trip, for its part, does not move: it depends on the operating budget (≈ 212 M$/yr), which stays the same regardless of who built the tunnel. A finished tunnel is run the same way, whatever TBM dug it. The cost per trip therefore stays around 3.85 $ at target ridership — still below the RTC's 8.90 $.

Straight-line amortisation over 50 years, without borrowing interest (same basis as the REM, the tramway and the Alto high-speed train, whose costs are always announced excluding financing — see the Price comparison page), plus 212 M$/yr of operation, divided by 200,000 users — before the revenue from an access fare, which would lower the net cost further in every scenario.

6. What does not change despite everything

Ruling out The Boring Company invalidates none of the project's technical foundations. The geology of Québec stays the same, as does the rock premium estimated to dig it. Conventional hard-rock TBMs — gripper, single or double shield — have been used for decades all over the world; it is an older and more proven technology than The Boring Company's, not less. A competitive tender among several bidders, rather than a single supplier, also fits more naturally with Québec's public-procurement rules — one more argument to make before the BAPE.

What this scenario changes is only the price. And even at its worst, that price stays in a class of its own against the region's other megaprojects — the REM excepted, barely.