Singapore underground: Imagine a city 50m below ground

Limestone deposits in western Singapore ideal for building caverns to store food and house people
Jermyn Chow, Straits Times 6 Apr 09;

NO SPACE in Singapore for buildings? Try digging underground.

In the west are limestone deposits - fertile ground for urban planners to build caverns that can be used to store water and food, or even house people.
A team of 10 geologists and researchers from the Defence Science and Technology Agency (DSTA) has found limestone deposits sitting underneath a 10km stretch of land from Telok Blangah to West Coast Road, including Kent Ridge and Boon Lay. Limestone and granite, both stronger than concrete, can also be found in Changi in the east.

Dr Zhou Yingxin, a DSTA senior principal engineer, said the abundance of limestone deposits, found 50m below ground, is enough to 'build an underground city'.

'We could replicate what you see above centres, schools, offices and streets, among other things,' he said, adding that a more detailed study will have to be done to determine the amount of underground space urban planners can tap on.

DSTA is documenting the presence of limestone deposits in Singapore's geological maps for the first time since they were first found in 1987 in Pulau Merlimau on Jurong Island. Its findings have been published in the second edition of Geology Of Singapore, first published in 1976.

So far, Singapore has used underground caverns for ammunition storage for defence forces. The Government is also building the first five caverns beneath Jurong Island to store crude oil and attendant oil products. They will start operations at the end of next year.

The DSTA, with geologists from the Nanyang Technological University and the Building and Construction Authority, studied soil samples over the past two years to compile the book.

It will be a useful reference for construction and urban planning experts as they continue to look for space to develop amid the concrete jungle.

The 90-page dossier also lists Singapore's oldest rock, in Pulau Tekong, and 200 million-year-old fossils in Jurong.

Another key finding is what lies underneath the city centre between Fort Canning Park, Middle Road and Telok Ayer Street: A hard rock, christened the Fort Canning Boulder Bed by the researchers.

Mr Michael Lee, who co-authored the book, said the sandstone boulder is three times tougher than concrete and a nightmare for civil engineers. 'It slows down and hampers excavation work, pushing up the construction costs,' said the geologist at the former Public Works Department.

He added that knowledge of this 'troublesome' rock, which is half the size of the Central Business District, is a bonus for construction companies.

Mr Colin Tan, senior project manager of local construction firm Tiong Seng, said the information will come in handy as contractors could halve the month- long soil investigation at some sites.