PUB, Singapore’s National Water Agency, has concluded tunnelling works on the second phase of the Deep Tunnel Sewerage System (DTSS). A ceremony to mark this important milestone was attended by Ms Grace Fu, Minister for Sustainability and the Environment, and more than 300 guests including pioneer engineers who started the DTSS project more than two decades ago.
The $6.5bn Phase 2 of the DTSS involves the construction of a 98km-long network of deep tunnels and link sewers, as well as the future Tuas Water Reclamation Plant. Split into sections, the South (Domestic) Used Water Tunnel is 28km with diameters ranging from 3m – 6m and tunnel depths of 35 – 55m, and the 7km long, 3.3m – 4m diameter, 45m – 55m deep Industrial Used Water Tunnel. Also constructed has been 63km of 0.3m – 3m diameter Link Sewers.
Spanning multiple tunnelling and construction contracts, the DTSS Phase 2 project involved over 5,000 workers at the peak of its construction works.
These new infrastructure components extend the DTSS network to serve the western half of Singapore, including the downtown area and upcoming developments such as Tengah Town and Jurong Lake District
Over two phases, the DTSS comprises a 206km-long network of deep tunnels and link sewers that will convey used water entirely via gravity to three centralised water reclamation plants located in Changi, Kranji and Tuas. The conveyance of used water via gravity instead of energy-intensive pumping stations enhances the robustness and reliability of the used water collection system.
Mr Goh Si Hou, PUB’s Chief Executive said, “As one of the most water-stressed countries in the world, the ability to effectively collect and recycle our used water in a closed water loop has been a game-changer in our quest for water security. The Deep Tunnel Sewerage System is not only an engineering feat, but a key pillar in strengthening Singapore’s water resilience to meet the long-term challenges of climate change and growing water needs. This has been made possible through the bold vision and innovation of our pioneers, and decades of meticulous planning and hard work by our planners, engineers and contractors. We look forward to the upcoming completion of our Water Reclamation and NEWater plants, which will realise the full potential of the DTSS in the years to come.”
Costing around $10 billion and designed to last for 100 years, the DTSS is an example of long-term water infrastructure planning and investment to benefit multiple generations. Due to its scale and complexity, the construction of DTSS had to be carried out in two phases.
Phase 1 of the DTSS serves the eastern half of Singapore and was completed in 2008. Tunnelling work for Phase 2, which commenced in 2019, was a challenging process through highly built-up areas that involved deep expertise and significant amount of preparatory work. The tunnelling works had to be carried out by five different contractors, using pioneering construction methods and smart technologies for safe and smooth operations. This served to greatly reduce disruption to above-ground infrastructure and the public.
The Phase 2 project has also implemented new features to ensure the integrity of the deep tunnels and ease of maintenance. These include the use of concrete resistant to microbiological-influenced corrosion, isolation gates to allow for flow diversion, fibre optic cables for remote monitoring of a tunnel’s structural integrity, and the use of air jumpers to control air flow within the tunnels.
A key component of DTSS Phase 2 is the future Tuas Water Reclamation Plant, which will be equipped with advanced technology to treat two separate streams of domestic and industrial used water in an energy-efficient manner. When ready in 2026, Tuas WRP will be co-located with NEA’s Integrated Waste Management Facility to form Tuas Nexus, Singapore’s first integrated used water and solid waste treatment facility that will be fully energy self-sufficient.
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