The streets will not carry superior vehicles or the like, but will be for the exclusive use of the knights. The carts and burdens must use the streets below. The toilets, stables and other fetid matter will also be relegated to the underworld. Thus, in the Renaissance, Leonardo Da Vinci sketched the great city, which was structured on two levels: the surface, for pedestrians, and a subterranean space for transport and services.
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Five centuries later, the Italian visionary’s ideas are more relevant than ever. Historically seen as the last line of defence, or for storage, the colonization of the subsurface is now being given a fresh start by the engineers and architects of the world’s mega cities.
This previously inhospitable environment is coming to the rescue of growing cities by allowing them to harness this growth without sacrificing living standards – or in some cases, even improving them. "It is an unstoppable trend," says Aniceto Zaragoza, general manager of the Spanish Cement Association, or Oficemen.
The number of cities with large underground infrastructure has quadrupled in three decades and in the past 10 years some 5,750km of tunnels have been constructed round the world.
The dynamic is so clear and present that for the first time in Spain, the Land Law introduced in 2008 give new rules expressly on this subject. "The cities showed a predisposition to grow under the asphalt, but there was no response in regulation. Subsoil construction was overlooked," explains Angela de la Cruz, deputy director general of the Ministry of Housing Urban Development. Traditionally, the clash of interests from owners and users of the different sides of the asphalt has led to numerous legal disputes. The Land Law is intended to solve these problems and meet the demands of many cities that came calling for specific legal treatment of the subsoil.
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By GlobalDataThis is the case of Madrid. In the last decade the city has built a dozen new transport interchanges, has allocated EUR 8.3bn (USD 10.66bn) to double its metro – the third largest in the world – and another EUR 4bn (USD 5.14bn) to underground power lines and substations. Spain’s capital holds a mirror up to cities such as Sevilla, which has only just realised the subsurface potential. Malaga is in the same position, while Pamplona and Zaragoza have begun burying their waste.
Following Canada’s lead
But even Spain’s most developed underground space is a far cry from the Canadian cities such as Toronto or Montreal, where people travel daily through tens of kilometers of tunnels filled with shopping malls, hotels and offices.
The logic is clear, according to Aniceto Zaragoza, by releasing the surface of cities, through burying many of our daily activities, city planners can transform the urban environment. Today it is congested, noisy and polluted. In the future it can return to a clean, quiet and pleasant space.
"The basement is an area to be exploited world wide. There is an opportunity to leverage the resources and make more room for the city," says Joaquin Mañoso, director general of Urban Planning for municipal households in Madrid. Cities are growing and the ground has become increasingly more expensive, scarce and non-renewable, especially as the world population soars. In 2050 it is expected to reach 9.2bn inhabitants, 60 per cent of who live in cities. In the West, this percentage is even greater.
According to the United Nations there are currently just nineteen megacities of more than ten million inhabitants, in 2050 there will be over 60. "This new infrastructure is needed to survive. "From an environmental and sustainability perspective there is no choice but to bring many of our activities underground," says Olivier Vion, ITA general secretary.
Colonisation disordered
"Everything that is done in the subsoil affects what is on the surface. Both levels cannot be separated," says Paloma Sobrini, dean of the Madrid College of Architects. Each action requires a thorough analysis of pros and cons, and the socioeconomic and environmental impacts must be considered. Different options must be studied. "Focus on efficient use of the space," Mañoso stresses, because, unlike surface works, underground construction is almost irreversible once built.
Institute of Technology Lausanne in Switzerland has developed a comprehensive view of the subsoil and three-dimensional urban planning for its Deep City project. "A new approach to multi level subsurface works allows cities to have a future compatible with sustainable development and improving the quality of life for citizens," say Laurent Tacher and Aurele Parriaux, two of the authors of the project. But against this view, practice shows that most underground infrastructure is planned on an ad hoc basis. For example, installing a freight logistics centre in the remaining gaps between underground lines.
A comprehensive approach is not always produced. A lack of foresight in planning, coupled with time pressures, budget pressures and a lack of coordination between administrations, is eroding the quality of many projects. "A sad example of the enormous social costs involved in failing to plan ahead is the Tunel de la Risa or Tunnel of Laughter. The tunnel links Atocha and Chamartín stations on the Madrid underground network. The twin bore tunnels are supported by a third tunnel that began construction in 2010 because the existing bores were too small for high speed trains," says Manuel Melis, professor of the Polytechnic University of Madrid and is considered the father of underground construction in the city. The new bore has cost the city EUR 206M (USD 264.6M).
A good business
These failures, however, are offset by the enormous environmental benefits and social and economic development that is generated by underground urban development. "The economic impact of these projects is brutal," emphasises Matthias Ildefonso Jimenez, general director of Metro de Madrid. For example, the line linking the capital with the main towns in the south of the region is used daily by 180,000 travellers. "This generates indirect benefits of EUR 380M (USD 489.9M) a year, making it possible to protect their investment in five years", Jimenez says. But besides generating indirect benefits, the metro has become an important source of work. It has a budget of EUR 1.3bn (USD 1.68bn) and employs more than 7,000 people. It houses hundreds of shops with a combined area of 1,000sqm.And there are plans to expand.
Underground car parks offer a return on investment in eight years and each of the 800,000 spaces is benefiting the local economy. Not surprisingly, therefore, there is a growing interest in colonising the underground space.
Considering that land is becoming more expensive and the cost of underground works despite being high, have fallen significantly, technological advances including TBMs and new materials have reduced the cost of tunneling in almost any terrain. It is cheaper, quicker and safer. "We hold the world record for time and cost," stresses a proud Edelmiro Rua, president of Spain’s College of Civil Engineers. In 2009, the country had constructed a 100km of metro at a cost of EUR 42M (USD 54.2M) per km, a third of the world average and far below the EUR 350M (USD 451.3M) per km seen on London Underground lines.
Subterranean highways, parking lots, fibre optic networks, power lines, water pipes and all kinds of similar infrastructure remain underground. But it is "only the tip of the iceberg," claims Aniceto Zaragoza. You can get much more underground. It is not science fiction to think that all transport of goods could be made through an underground network. Some Asian cities have already buried logistics centres or waste treatment plants, or constructed a road network, or a network of parking lots. There are already offices or shopping malls underground in many major cities. Next will come factories. For now, Spanish rules are very restrictive in this sense but who knows.
"We do not plan to live in the basement. But many activities could migrate to the subsurface that do not require natural light. At the mall, for example, there is no rational difference between being above or below ground. There are no windows"
