Singapore

Work starts for phase two of underground sewage tunnels

Phase two of construction for a $10 billion underground sewage superhighway, one of the world's largest, started yesterday.

The Deep Tunnel Sewerage System (DTSS), which will be the conduit for all used water islandwide, will boost water recycling and free up space in land-scarce Singapore.

When completed in 2025, the sloping infrastructure of giant pipes will harness gravity to channel used water in the western parts of the island to a new water reclamation plant in Tuas.

Phase two of the project by water agency PUB, which costs $6.5 billion, will also free up an additional 83ha of land - about the size of 116 football fields - currently housing the Ulu Pandan and Jurong Water Reclamation Plants, about 70 pumping stations and many more sewage treatment plants.

Minister for the Environment and Water Resources Masagos Zulkifli marked the start of construction at a ceremony in Penjuru Road in Jurong East.

He said: "We have experienced how unpredictable weather patterns can be, and we expect dry seasons to worsen with climate change.

"It is therefore critical to augment our water sources by reclaiming water, so it can be used again and again, in an endless cycle."

DTSS Phase 2 will boost Singapore's Newater supply, he added. It will eventually channel all of the island's used water to water reclamation plants in Changi, Kranji and Tuas, where it will be treated and purified to either produce Newater or be discharged into the sea.

The tunnels, which sit under the Republic's rail network and above its electricity grid, slope downwards towards the three plants as they are dug at a gradient.

Phase 1, which cost $3.4 billion, was completed in 2008. It serves the eastern parts of Singapore, channelling used water to the Kranji and Changi Water Reclamation Plants.

DTSS Phase 2 will stretch 30km across the western part of Singapore, starting under Keppel Road, at 35m below ground, following the Ayer Rajah Expressway all the way to Tuas Road, where it will be 55m below ground.

It will also include a separate 10km tunnel in Tuas for industrial used water.

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PUB has appointed five contractors to design and build the tunnels.

The 30cm-thick tunnels in DTSS Phase 2 will be constructed with several safety features, including embedded fibre optic cables in the concrete lining to monitor the structural integrity of the tunnels remotely and detect cracks.

There will be 18 shafts to allow human access. Air jumpers, essentially giant fans within the tunnels, will be used to direct sewage fumes to four odour control facilities.

The tunnels are expected to last 100 years.

Environment