PUB explores underground space for drainage and water storage in Singapore

PUB could unearth Singapore's water solutions
It's exploring underground drainage, reservoir system to fight land crunch
By Audrey Tan, The Straits Times, 17 Jun 2015

SINGAPORE could soon be digging deep for an answer to its water challenges.

National water agency PUB is looking into creating underground reservoirs that will bypass the space crunch above ground, said Minister for the Environment and Water Resources Vivian Balakrishnan yesterday.

Tapping such structures will also help the city better deal with climate-change effects, such as more intense rain and prolonged dry spells, as excess water can be stored and used when needed.

"In Singapore, we receive an average of about 2.4m of rainfall a year... In theory, we should not be short of water... The real limiting factor is not rainfall, but land," Dr Balakrishnan said at the opening of the inaugural Singapore International Water Week Technology and Innovation Summit (STIS) yesterday. The two-day water conference which focuses on research and development is a prelude to the Singapore International Water Week next year.

The underground drainage and reservoir system is likely to have three key components: tunnels to channel storm water below ground, caverns for water storage, and a pumped storage hydropower system, which can convert energy from water flowing into underground caverns to electrical energy. This can be used to pump the water back to the surface.

Such systems have long been championed by experts here as solutions to weather fluctuations and land scarcity.

One of them, Professor Lui Pao Chuen, a National Research Foundation adviser who spearheaded research into Singapore's underground ammunition facility, noted: "One-third of Singapore is made up of granite rocks, which are very strong, and rock caverns for underground reservoirs can be constructed there."

PUB deputy chief executive of policy and development Chua Soon Guan said a tender for a two-year feasibility study on building such a system will be called in the next few months. Expected to be completed at the end of 2017, it will include geological surveys on soil and rock properties, and look into design options.

The agency's director of policy and planning William Yeo stressed that it will work with relevant agencies and stakeholders to ensure that the surveys are "conducted with care and sensitivity to the environment".

Geological studies are essential since the underground storage reservoir must be built on rock mass instead of softer soil which may not be able to support it, said Mr Chong Kee Sen, president of The Institution of Engineers, Singapore.

Associate Professor Tan Soon Keat, director of the Nanyang Technological University's Maritime Research Centre, said building in a rocky area would also ensure there is less water loss and prevent the water from being contaminated by soil minerals.

PUB would not comment on possible locations or other details, but the three experts believe it could be located in the central or north-eastern part of Singapore.

Prof Lui, who is also a former Ministry of Defence chief defence scientist, said that the rock mass west of the Bukit Timah Expressway offers many potential sites.

"The optimal location will be determined by the connection to above-ground reservoirs and the drainage system for storm-water harvesting," he explained.

Paving the way for underground water storage is Bidadari's service reservoir, which holds potable water. Work on the reservoir is likely to start in early 2017.

Underground reservoirs are another step towards creating a subterranean metropolis here.

Earlier this year, two Bills to pave the way for underground development were introduced after a proposal by National Development Minister Khaw Boon Wan for an underground master plan.