The Deep Tunnel Sewerage System (DTSS) provides a cost-effective and sustainable solution to support Singapore’s continued growth, and meet its long-term used-water infrastructure needs.

The project uses deep tunnels to convey used water by gravity to centralized water reclamation plants (WRPs) located at the coastal areas. The used water is then treated and further purified into ultra-clean, high-grade reclaimed water known as NEWater, with excess treated effluent discharged to the sea through an outfall.

AECOM, along with joint venture partner Black & Veatch, was appointed by the Public Utilities Board (PUB), Singapore’s National Water Agency, as the professional engineering services consultant overseeing the development, engineering, and construction of DTSS Phase 2, which covers the Western and Southern parts of Singapore. The tunnelling works for Phase 2 had been completed in 2023.

The project includes 40 kilometers of deep tunnels running largely under the Ayer Rajah Expressway, which will connect with the existing used water infrastructure to create one seamless and integrated system. In addition, 60 kilometers of link sewers will create an interconnected network to channel used water from the existing sewerage pipelines to the deep tunnels.

Meeting Singapore’s water demands

A highlight of Phase 2 will be the construction of the new Tuas WRP, which will contribute to Singapore’s long-term goal of increasing NEWater supply to meet up to 55 percent of total water demand, further strengthening water sustainability and resilience for the nation.

“To maximize the potential synergies of the water-energy-waste nexus, the co-location of Tuas WRP and the Integrated Waste Management Facility (IWMF) marks Singapore’s first initiative to integrate used water and solid waste treatment processes. Synergies between the two plants will maximize both energy and resource recovery. The co-location will also be the first facility of its kind in the world planned from the ground-up.”

Robert Chan, Vice President, Water, Asia, AECOM

Upon completion, the DTSS scheme will result in a reduction in land taken by used-water infrastructure, with three centralized collection and treatment points at Changi WRP, Kranji WRP and Tuas WRP in the west. The existing conventional WRPs at Ulu Pandan and Jurong, as well as intermediate pumping stations, will be progressively phased out and the land freed up for higher value development.