There’s no shortage of work out there, either. China recently completed a 20-kilometer railway tunnel in the Longmen Mountains after a decade of construction. There’s the HS2 rail project in the UK, which will connect London to towns and cities in the north of the country and is set to feature more than 100 kilometers of tunnels along its proposed route. And Peter Vesterbacka, who used to work for Angry Birds developer Rovio, is behind an ambitious plan to build an undersea tunnel between Finland and Estonia. These are but a few examples.

Amberg forecasts increasing demand for underground infrastructure in the future—not least as a means of escaping rising temperatures above ground due to climate change. “It’s maybe not so bad to have a place where we have more constant temperatures,” she says.

Tunnels aren’t just for transportation. Troy Helming, founder and CEO of San Francisco-based startup EarthGrid, emphasizes the need to put power lines underground—this is what his company aims to do. The vast majority of transmission cables are above ground in the United States and Canada, he notes, leaving them exposed to hurricanes and other storms as well as, increasingly, wildfires.

“Our plan is to put a supergrid across North America,” he says, proffering a map with colored lines showing said grid stretching all the way from the eastern seaboard to the Pacific Ocean, and future offshore wind farms in the west. It’s a plan that could help link up the fragmented US grid—and potentially one day even extend as far as Europe, to tap the huge offshore wind potential there. “It’s crazy and audacious, and we know that,” says Helming.

One hurdle is the extremely tough rock, such as granite and quartzite, that makes traditional excavation in some of these places difficult or impossible. Helming is betting on plasma torch technology that heats rock to about 6,000 degrees Celsius, blasting it to smithereens, as the solution. He suggests that this could allow for the creation of tunnels in hard rock 100 times faster than with current technology. EarthGrid is developing a prototype robot wielding five plasma torches, which Helming says should be ready for testing in March 2023. The firm also aims to complete its first, small-scale commercial project by the end of this year.

Helming notes that, in EarthGrid’s case, the tunnels will not be circular in shape but rather a traditional horseshoe—imagine a square with an arch on top, instead of a flat ceiling. This, he argues, makes it easier to install cable racks or, in larger transportation tunnels, a road surface on the flat base of the tunnel.

Rival company Petra also aims to bore through tough rock using the power of heat, though with a thermal cutting device that uses a superheated fluid rather than with a plasma torch. The idea is to slice through “nightmare geologies” with relative ease, says CEO and cofounder Kim Abrams.

“We finished a 34-foot, 30-inch-diameter tunnel in granite just last week,” she says, adding that the firm hopes to begin commercial work next year. And she mentions that the company is also working on a separate solution to tackle the other end of the spectrum—extremely soft or water-logged soil, such as is often found beneath and near coastal cities.

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