A finished basement can be a beautiful thing. With the right accoutrements and enough effort, what might otherwise be a damp, empty space lined with concrete can be turned into a cozy playroom, or a den, or an office and gym. Properly planned, the basement can become an integral part of a household, even a kind of engine that powers it from below.
The same is true for the far larger basement that all of us share: that vast space that exists under our feet wherever we go, out of sight and out of mind. Those of us who are city-dwellers already keep a lot of stuff down there—subway stations, sewer pipes, electrical lines—but as our cities grow more cramped, and real estate on the surface grows more valuable, the possibility that it can be used more inventively is starting to attract attention from planners around the world.
“It used to be, ‘How high can you go up into the sky?’” said Susie Kim, of the Boston-based urban design firm Koetter Kim & Associates. “Now it’s a matter of, ‘How low can you go and still be economically viable?’”
A cadre of engineers who specialize in tunneling and excavation say that we have barely begun to take advantage of the underground’s versatility. The underground is the next great frontier, they say, and figuring out how best to use it should be a priority as we look ahead to the shape our civilization will take.
“We have so much room underground,” said Sam Ariaratnam, a professor at Arizona State University and the chairman of the International Society for Trenchless Technology. “That underground real estate—people need to start looking at it. And they are starting to look at it.”
The federal government has taken an interest, convening a panel of specialists under the banner of the National Academy of Engineering to produce a report, due out later this year, on the potential uses for America’s underground space, and in particular its importance in building sustainable cities. The long-term vision is one in which the surface of the earth is reserved for the things we want to see and be around—houses, schools, yards, parks—while all the other facilities that are needed to make a city run, from water treatment plants to data banks to freight systems, hum away underground.
Though the basic idea has existed for decades, new engineering techniques and an increasing interest in sustainable urban growth have created fresh momentum for what once seemed like a notion out of Jules Verne. And the world has witnessed some striking new achievements. The city of Almere, in the Netherlands, built an underground trash network that uses suction tubes to transport waste out of the city at 70 kilometers per hour, making garbage trucks unnecessary. In Malaysia, a sophisticated new underground highway tunnel doubles as a discharge tunnel for floodwater. In Germany, a former iron mine is being converted into a nuclear waste repository, while scientists around the world explore the possibility of building actual nuclear power plants underground.
Overall, though, the cause of the underground has encountered resistance, in large part because digging large holes and building things inside them tends to be extremely expensive and technically demanding. Boston offers perfect examples of the pluses and minuses of the endeavor: Putting the Post Office Square parking lot underground created a park and a beloved urban amenity, but the much more ambitious Big Dig turned out to be a drawn-out and unspeakably costly piece of urban reengineering.
And perhaps an even greater obstacle is the psychological one. As Ariaratnam put it, “Even in a condo tower, the penthouse on the top floor is the most attractive thing—everyone wants to be higher.” The underground, by contrast, calls to mind darkness, dirt, even danger—and when we imagine what it would look like for civilization to truly colonize it, we think of gophers and mole people. Little wonder that our politicians and urban designers don’t afford the underground anywhere near the level of attention and long-term vision they lavish on the surface. In a world where most people are accustomed to thinking of progress as pointing toward the heavens, it can be hard to retrain the imagination to aim downward.
PEOPLE HAVE BEEN making use of underground space for thousands of years—to stay warm, to stay dry, and to stay safe. In Cappadocia, now part of Turkey, early Christians used an elaborate network of tunnels to protect themselves from Roman armies, carving out underground cities so intricate they attract tourists to this day. As technology improved, the range of uses expanded. In the 1860s, London began putting its railways underground and created the first subway. A hundred years later, Montreal started work on an elaborate underground shopping mall. Military applications proliferated as well: The second half of the 20th century saw the construction of backyard bomb shelters across the United States, as well as the secret military complex of NORAD deep inside Cheyenne Mountain in Colorado and an underground Soviet submarine factory in Ukraine.
Today’s push underground is motivated not so much by safety or commerce as by the drive to conserve space and resources. According to current projections, the world’s population will grow to 9.3 billion by 2050, and two-thirds of those will be living in cities. That means that demands on urban infrastructure will soar: We will need more energy, more water, more waste disposal, and above all, more room for homes and roads. To expect it all to happen on the surface is to invite an uninspiring, resource-sapping sprawl.
“As cities are built up, they’re getting congested, and going underground is the only way to build capacity,” said Youssef Hashash, a member of the National Research Council committee and a civil and environmental engineering professor at the University of Illinois. He added: “Many of the things we’ve built above ground can be pushed underground.”
Hong Kong, one of the world’s densest cities, recently started exploring the possibility of putting some 400 “unsightly” government facilities underground, according to the South China Morning Post—including sewage treatment plants, water reservoirs, fuel storage depots, and columbariums for cinerary urns. In Chicago, meanwhile, a multibillion dollar project aimed at using underground tunnels and reservoirs to prevent flooding and contain polluted storm water has been underway since the 1970s. And in Germany, a company called Cargo Cap has been developing a freight transport system that would take trucks off the road and instead allow companies to shuttle goods out of a city through buried pipes.
“The thought is to use this ground surface for what we call more noble purposes,” said Harvey Parker, a former president of the International Tunnelling and Underground Space Association. “Putting transit underground, putting electrical services, sewers and so on, allows you...to leave the ground surface unobstructed for natural beauty.”
Proponents of underground construction like to talk about the ground’s natural assets. For one thing, it is perfectly insulated, keeping a temperature in the low 50s, and is thus inexpensive to heat and cool. It also has some safety features: Underground facilities are protected from tornados, hurricanes, and other natural disasters. For this reason, some engineers and scientists have been advocating for underground nuclear power plants, arguing that they would be less dangerous in the event of an explosion, because whatever radiation they produced would be naturally contained.
Not all underground facilities are strictly infrastructure-related. There are also those that are designed for people, creating spaces for activities that most of us used to doing above ground. In Kansas City, Mo., converted limestone mines are leased by the square foot for manufacturing and storage. (Tenants of one complex, called Subtropolis, include a barbecue chain that keeps its meat and sauces down there, and the US Postal Service, which uses the space to store collectible stamps.) In New York, conceptual designs have been drawn up to transform a deserted trolley station into a leafy underground park—“the
LowLine”—using an innovative mechanism involving fiber-optic cables to capture daylight. Underground malls protect shoppers from Singapore’s heat and Canada’s winter cold; in mountainous Norway, meanwhile, there are multiple underground swimming pools and an underground stadium that plays host to sporting events and concerts.
But even the most avid proponents of underground development agree that it’s unlikely that underground housing or even office space will become common any time soon—too many people feel unsafe, claustrophobic, or disoriented spending extended periods of time underground. Indeed, being in a confined space can be risky when something goes wrong. One study found that although traffic accidents are less frequent in tunnels than on open roads, the chances of being killed in such an accident are higher. Fire can also be particularly perilous when it breaks out underground—a 2003 arson incident in a Seoul metro station left almost 200 dead—which means it’s crucial to have in place powerful ventilation systems, well-defined emergency procedures, and a high degree of compartmentalization, to prevent the spread of smoke and flames.
As for the more psychological effects of underground life, engineers and designers are chipping away at the problem of how to make underground facilities feel less alienating. Working on the design of an underground research laboratory in South Dakota, where scientists would be spending long hours 8,000 feet under the earth’s surface, Craig Covil—a principal at the engineering firm Arup, who is also working on the LowLine—said he and his team considered imaginative design techniques involving air flow, acoustics, and light that would essentially “trick” people’s senses and reduce the discomfort they might otherwise feel.
AS UNDERGROUND ENTHUSIASTS work to spread their message—Harvey Parker, for instance, has spoken at United Nations workshops to make the case for underground space—engineers are focused on dismantling the perception that what’s under the ground is somehow fundamentally separate from what’s on the surface. In essence, they want people—politicians and city planners, especially—to start seeing it as a basement to be finished, or another neighborhood to be developed.
The initial problem is cost: Although underground structures might have lower long-term costs, building underground is always going to be more expensive in the short term. That makes it very difficult to convince political leaders to do it when they have an alternative. “We choose the cheapest option because everyone’s always worried about their current budgets,” said Raymond Sterling, a professor at Louisiana Tech University and coauthor of the book, “Underground Space Design: A Guide to Subsurface Utilization and Design for People in Underground Spaces.”
Sterling and his allies want developers and city planners to take more of a long view, and to approach underground planning in a more centralized, holistic way. Right now, projects are undertaken in a piecemeal fashion, with little regard for how else the underground space might one day be used. “What we should do is to begin planning the underground to the same degree that we plan the surface,” said Parker. “We have planning committees and so forth that say, ‘This area is an industrial area’ or, you know, ‘This is a high rise district.’ Planners should do the same kind of thing for underground aspects of cities.”
As aggressively as cities zone their surface neighborhoods, that’s not very common yet. Engineers heap praise on the few cities that have taken steps in that direction—especially Helsinki, where officials have put forth an “underground master plan” that provides guidelines for and restrictions on underground construction with an eye toward using the space as efficiently as possible.
What will it take for other cities to follow suit? For a hint, Sterling suggested taking a look at Singapore: a massively overcrowded city-state with a population of more than 5 million people that has taken up the cause of underground development with gusto out of sheer necessity. “All of the big owners of land there are under pressure from the government to see how they can use their land more efficiently,” said Sterling. In many cases, that means looking under their feet—for the simple reason that there’s nowhere else to look.