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Construction begins for S$6.5 billion, 100km superhighway for used water

SINGAPORE — Construction work began on Monday (Nov 20) on a 100km underground “superhighway” to transport used water to water reclamation plants, which when completed in 2025, allows 83ha of land to be freed up.

Construction begins for S$6.5 billion, 100km superhighway for used water

Minister Masagos Zulkifli attends the Tunnel Groundbreaking Ceremony of PUB's Deep Tunnel Sewerage System Phase 2, on Nov 20, 2017. Photo: Jason Quah/TODAY

SINGAPORE — Construction work began on Monday (Nov 20) on a 100km underground “superhighway” to transport used water to water reclamation plants, which when completed in 2025, allows 83ha of land to be freed up.

This second phase of the deep tunnel sewerage system (DTSS), estimated to cost S$6.5 billion, will serve the western part of Singapore, including the downtown area and upcoming major developments such as Tengah Town and Jurong Lake District.

It will run largely under the Ayer Rajah Expressway, starting from Keppel Road, crossing undersea at Tuas Bay, and end at the upcoming Tuas Water Reclamation Plant, where a new NEWater factory will be built.

Above: A map highlighting the different phases of the Deep Tunnel Sewerage System. Illustration: PUB)

The sloping deep tunnels of the DTSS convey used water from homes and industries by gravity to various water reclamation plants. The used water is then treated and purified into NEWater or discharged into the sea.

When completed, the deep tunnels in the second phase will be connected to those built in the earlier phase — completed in 2008 — to serve the eastern part of Singapore, and the public sewer network.

Speaking at a groundbreaking ceremony on Monday, held at the first tunneling shaft for this phase of the project in Penjuru Road, Minister for the Environment and Water Resources Masagos Zulkifli said Singapore’s NEWater supply will be boosted to up to 55 per cent of the water demand here, when the DTSS is fully up and running with the completion of the second phase.

Currently, NEWater meets 40 per cent of the Republic’s water demand.

Mr Masagos called the DTSS a “key strategic asset” in enhancing Singapore’s water security. Singapore has also experienced unpredictable weather patterns and can expect dry seasons to worsen with climate change.

“It is therefore critical to augment our water sources by reclaiming water so that we can use it again and again, in an endless cycle,” he added.

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(Video: PUB)

The existing water reclamation plants at Ulu Pandan and Jurong, and the intermediate pumping stations can also be progressively phased out, once the second phase is completed.

Combined with the land freed from phase one of the project, the DTSS will halve the amount of land taken up by used water infrastructure, from about 300ha in the 1990s to 150ha in the long term.

The total size of the land freed up for higher value development is equivalent to about 214 football fields.

In response to TODAY’s queries on redevelopments on land freed up by the first phase of the DTSS, a spokesperson of the Singapore Land Authority said the site formerly occupied by the Seletar Water Reclamation Plant has been turned into Seletar Aerospace Park.

Where Kim Chuan Water Reclamation Plant stood is being used for industrial development — Defu Industrial City — and for the development of Integrated Construction and Prefabrication Hubs, she said.

Above: A boring rig seen at the Tunnel Groundbreaking Ceremony of PUB's Deep Tunnel Sewerage System Phase 2, on Nov 20, 2017. Photo: Jason Quah/TODAY

The parcel that Bedok Water Reclamation Plant sat on is zoned for industrial and utility uses, she added.

Director of DTSS Phase 2 Yong Wei Hin told reporters that tunneling over 100km of land in Jurong could be challenging, given the geology of the area. There are a lot of sedimentary rock and cavities, which are not ideal for tunneling, he noted.

Nineteen Tunnel Boring Machines will be used to dig at depths of between 35m and 55m below ground and under the sea, which is deeper than some of the underground MRT lines.

Advanced technologies will also be used in the operations and maintenance of the tunnels, said a spokesperson from national water agency PUB.

Illustration: PUB

For instance, the deep tunnels will be lined to protect them against corrosion from bacteria and other micro-organisms. Sections undersea will also have an additional water-tight membrane. These features are expected to make the tunnels last 100 years.

Along the tunnel above ground, devices called air jumpers will be installed to push odorous air rising from the tunnel to odour control facilities downstream and away from residential areas.

Singapore’s water comes from four “national taps”. About half is imported from Johor, Malaysia under two bilateral agreements. The first one expired in 2011 and the second, signed in 1962, will lapse in 2061.

Singapore has had dry weather and Johor has also experienced water supply issues in recent years.

The rest come from NEWater, local catchment areas and desalination. By 2020, the Keppel Marina East Desalination Plant, the first large-scale desalination plant that can treat both seawater and freshwater, will begin operations. In that same year, a fifth desalination plant on Jurong Island will also open.

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