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Adding Space by Going Kilometres Beneath the Surface

Historically, Singapore has built upwards by erecting ever higher buildings, and outwards by reclaiming land from the sea. Increasingly, it is digging deep to optimise land beneath the surface.

In addition to the ever-expanding MRT network, pedestrian links and shopping centres, we now have a five-lane Marina Coastal Expressway, a district cooling network, an ammunition facility and an oil storage facility underground.

The latest facility to go beneath the surface is a 230-kilovolt electrical substation in Pasir Panjang. Built by power company SP Group below a new commercial building, it will be Singapore’s largest substation when completed in 2025.

There is much more to come as common utilities traditionally found above ground like electric cables are going underground. SP has just completed three underground cable tunnels spanning 40 kilometres across Singapore in depths of 60 to 80 metres beneath the earth. Over the next three years to 2022 it will progressively lay cables. When fully installed, they will be able to carry 20% of Singapore’s current electricity supply.

National water agency PUB is studying if underground water storage is viable on a large scale.

The interest in Singapore’s underground resource was stirred by Minister Khaw Boon Wan in his blog post in 2013. Mr Khaw, who was then National Development Minister, suggested that Singapore could do much more with its underground spaces, much like in Montreal and Scandinavia. Much of central Montreal is connected by an “underground city” of tunnels while Scandinavia has located swimming complexes, utility plants, concert halls and churches below the city streets.

To facilitate development, the government in 2015 made the necessary legislative changes empowering it to acquire stratas of underground space under private land, paving the way for a future underground metropolis.

The Singapore Land Authority has collated underground data on its Integrated Land Information Service. Available online, it allows industry players, such as construction companies, to purchase utility plans. Previously, these plans have to be purchased from the different utility providers.

Freeing Land Above Ground
By digging deep, Singapore has been able to free up much-needed space. The Jurong Rock Caverns – the first underground oil storage facility in Southeast Asia – lies about 150 metres below ground on Jurong Island. Taller than a 30-storey housing block, the five caves create 61 hectares of space below the Banyan Basin with 9 kilometres of access tunnels built around them. Each cavern measures 27 by 20 by 340 metres, equivalent to 64 Olympic-sized pools.

Opened in 2014, the S$1.7 billion project freed up 60 hectares, equivalent to 84 football fields, of useable land. There are plans for a phase two development, which is expected to double its current capacity.

The Underground Ammunition Facility for live ammunitions and explosives lies over 100 metres deep under the old Mandai Quarry. Having it underground required 90% less land to be sterilised than a comparable above-ground ammunition depot. It also freed up another 300 hectares of land, equivalent to 400 football fields or half the size of Pasir Ris New Town.

Despite its huge potential, the development of underground space can be challenging. Development cost is much higher and complexities in planning and development are significant. The consequences of any sloppy workmanship are also dire, as Mark Wallace, an engineer in London-based ARUP Group, told Smithsonian.com. “If you are going to build underground, you should do it properly. Tall buildings are dead easy to take down. The underground? Not so easy.”

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