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Engineering underground space

Global cities must start developing underground space to free up traffic and reduce urban blight.

When London mayor Boris Johnson recently commissioned studies into the benefits of moving key London roads underground, it marked a small victory for campaigners who argue that the city needs to think downwards to deal with its traffic problems.

Inspired by a visit to Boston’s Big Dig road tunnel scheme, Johnson showed he had fully bought into the philosophies espoused by parts of the engineering community, and CH2M Hill senior fellow of technology Martin Knights in particular.

Knights is chief advocate of London’s Hammersmith Flyunder scheme – a tunnel to replace the ageing Hammersmith Flyover. He argues that some of the prohibitive costs associated with putting arterial routes or other infrastructure underground could be offset by the financial advantages of unlocking surface space above.

“By 2050, it’s forecasted that 70% of the global population is going to be living in urban areas”

Hans Admirall, Itacus

Speaking at the ICE’s Engineering Underground Spaces conference last month, Knights drew on further international examples to prove that the underground lobby was gaining momentum.

“Sydney has transformed gridlock into free-flowing traffic by putting something like 8km of highways underground,” he said. “In Hamburg they’re greening over a 3.5km section of the A7 Autobahn to reconnect communities. These are real projects and not just a dream.”


The Giken cylindrical underground cycle parking system, already in use across Japan

In a joint presentation at the same event, Antonia Cornaro and Han Admiraal from the International Tunnelling Association’s Committee on Underground Space (Itacus) said global cities would have to work downwards to deal with overcrowding and climate change.

“By 2050, it’s forecasted that 70% of the global population is going to be living in urban areas,” said Itacus chair Admiraal. “That means the same number of people who live on the planet now will live in urban areas by that date. Underground space can be a spatial relief valve, but if we only use it to rid ourselves of the urban blight it will just become an urban service layer while it could be so much more.”

All of the speakers admitted that cost was the biggest obstacle to taking infrastructure underground. But Knights said the example of the Boston Big Dig proved the financial benefits associated with turning a flyover into a “flyunder”.

“The surface space that has been freed up in Boston is vast,” he said. “At one stage people were living in multi-storey properties looking at a viaduct. Now what you’ve got is green land and the value of that property zooms up. The indirect taxation you can get from that helps you to fund some of the capital works that you need for the operation of the tunnels. In next 15 years the Big Dig will have paid for itself mainly through taxation and the commercial benefits of exploiting the better urban realm at the surface space.”

But regardless of the financial benefits, Cornaro, who is ITACUS vice chair said there were examples of situations in which planners had no choice but to think downwards. She pointed to the example of the Louvre in Paris where there was no space to build new gallery space above ground and the museum’s art collection needed to be protected from sunlight.

“Similarly, the city of Singapore has proposed an underground science city to connect two existing biomedical facilities,” she said. “It can’t connect them above ground because there is a protected park there. It’s undergoing a pre-feasibility study right now.”

Cornaro added that cost might be less prohibitive in situations where underground space already existed. She referred to the example of an old air-raid shelter in Helsinki that had been converted into an underground swimming pool and plans to develop a disused tram shed in New York into an underground park (see box).

Knights suggested that Helsinki was a leader in its approach to underground planning. “Cities like Helsinki are showing the way by having a coordinated strategic masterplan for the use of surface space and also the underground [environment],” he said.

All of the speakers agreed that engaging with politicians and the public would be important in getting projects like the Hammersmith Flyunder off the ground – or rather underground. Vivid language would also have a role to play.

“Boris Johnson coined the phrase ‘tunnellising’ to describe this type of project which nicely introduces the concept to the public,” said Knights. “The word ‘flyunder’, which I can take credit for, is also a way of using contemporary language to connect with the media and the public.” 


Tokyo, Japan – automated bicycle parking

With increasing numbers of commuters cycling to work, facilitated by segregated bicycle lanes, international cities are having to think about setting up bike storage infrastructure to prevent overcrowding and illegal parking. Japanese construction solutions company Giken Seisakusho has come up with a cylindrical, earthquake-resistant underground parking system which can be buried below the streetscape.


Dubbed Eco Cycle, the structure, which has already been used in various cities around Japan, measures 8.5m in diameter, has a depth of 11.6m and can store up to 204 bicycles.

Interestingly, Giken uses a silent and vibration-free “press in” in piling technique to form the cylindrical wall for the storage structure.

The machine derives the reaction required to install the steel piles by gripping previously installed piles, allowing the press in machine to self-walk along the pile top.

The guiding principle behind the Eco Cycle product is “culture above ground, function below ground.”

Montreal, Canada

Private developers have used underground space as a respite from the cold winter climate and the extremely hot summers in Montreal.

The underground space is reportedly based on an idea by Leonardo da Vinci. Begun in the 1960s, it is now the world’s largest underground city containing 31km of passageways, 10 metro stations, a railway station, a bus terminal, more than 1,600 shops, 200 restaurants, 40 banks and 30 cinemas.

Itacus vice chair Antonia Cornaro says: “Montreal shows us what we’re lacking in other cities. We have urban transport nodes and of course we connect our stations to these nodes and often we have some retail around these nodes, but often we don’t connect the spaces underneath.”

Montreal underground city

Viikinmäki wastewater treatment plant, Helsinki

The Viikinmäki wastewater treatment plant in Helsinki is one of the largest underground spaces in the world and bears testimony to the city’s enlightened approach to underground planning.

Viikimarki wastewater underground

Excavated into the Helsinki granite in 1994, it was built underground because this was the only way to gain planning permission for an unsightly plant.

An underground plant can also operate without being exposed to freezing temperatures above ground. The underground environment and a single ventilation track also provide the plant with the opportunity to monitor gas emissions data and improve odour management.

It also freed up space for a leafy park and 24ha housing above ground.

Boston Big Dig

Eyebrows would have been raised in the engineering community when London Mayor Boris Johnson said the Boston Big Dig could inspire London to re-imagine how it manages traffic and improves urban planning.

Boston Big Dig

The $15bn (£9.3bn) Big Dig tunnel project was plagued by unforeseen ground conditions, leaks, fallingdebris and a £900M overrun. To be fair to Johnson, he was probably referring to the above ground impact of the project rather than the way it was delivered. Since the tunnel opened, the average time to get through Boston has nearly halved and a CH2MHill study has estimated the travel time and vehicle operating cost savings to Boston citizens amount to £110M per year. The project also freed up 16M to 21M sq ft of the South Boston Seaport district for new commercial and residential development. Taxation from the newly created district has helped to pay for the Big Dig.


New York Lowline

The proposed New York Lowline project is a private initiative which involves converting a disused tram terminal on the Lower East Side of Manhattan into an underground park by using remote skylights to gather and reflect sunlight into the space.

New York Lowline


Engineers from Arup conducted a study for the project, which concluded that the Lowline was technically feasible and would also improve the local economy and adjacent transit hub.

Advocates for the project have started a fundraising campaign on the crowdsourcing Kickstarter website to raise money for the project and are negotiating with the Mass Transit Authority and the city authorities to build and operate the park.

If negotiations are successful they will then launch a capital campaign to support construction. It is predicted that the underground park could open in 2018.

Hammersmith flyunder, London

CH2M Hill senior fellow for technology Martin Knights says the Hammersmith “Flyunder” started off as a “jolly good wheeze” for engineers at CH2M Hill subsidiary Halcrow.

The company’s offices sit right next to the Hammersmith Flyover, a structure which Knights describes as “one of the biggest urban blights in West London”. The engineers in question came up with a proposal to free up space above ground for development and to reconnect communities to the north and south of the flyover by placing the highway below ground.

Hammersmith flyunder

The socio-economic benefits could then be used to pay for the project. Knights reveals that he has even had an enquiry from the Football Association about using the freed up space to develop football pitches.

But he says the project currently finds itself in a “chicken and egg” situation. “You can’t design the tunnel if you don’t know what sort of development will exist above it, and you can’t get the funding unless you can prove that the above ground development will pay for the project,” he says.

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