PUB breaks ground for the construction of DTSS Phase 2 conveyance system

Singapore’s national water agency, PUB, recently held a groundbreaking ceremony for the enhanced conveyance system of the Deep Tunnel Sewerage System (DTSS) Phase 2 to mark the start of the construction work. Officiated by the Guest of Honour, Mr Masagos Zulkifli, Minister for the Environment and Water Resources, the ceremony was held at the site of DTSS Phase 2’s first tunnelling shaft at Penjuru Road.

The deep tunnels in Phase 2 will connect with the existing deep tunnels in Phase 1 that serve the eastern part of Singapore as well as the public sewer network to create one seamless integrated system. When Phase 2 is completed in 2025, all of Singapore will be served by the DTSS.

Used water will be conveyed from the DTSS via gravity to three centralised water reclamation plants for treatment before it undergoes further purification to produce NEWater, or discharged into the sea.

To be constructed using the tunnelling method, the massive 100-kilometre (km) used water conveyance network for DTSS Phase 2 will run largely under the Ayer Rajah Expressway (AYE), crossing undersea at Tuas Bay, and ending at deep shaft inlets within the future Tuas Water Reclamation Plant.

19 Tunnel Boring Machines will be used to dig at depths of between 35 metres to 55 metres below ground as well as under the sea to create 40km of deep tunnels and 10km of link sewers. The remaining 50km of link sewers will be constructed using a micro-tunnelling method known as pipe jacking.

The conveyance system in Phase 2 will incorporate advanced technologies to enhance its operations and maintenance. Engineered for an operational life expectancy of a century in a corrosive sewer environment, the deep tunnels will be lined for corrosion protection – especially against microbiologically-influenced corrosion, with an additional water-tight membrane coating the tunnel section running undersea. The deep tunnels will also be the first project in Singapore to use air jumpers in the operations of its air flow management system.

Advanced maintenance features of the deep tunnels include the use of embedded fibre optics for remote sensing and monitoring of structural integrity, and tunnel shafts innovatively designed with gates to isolate tunnel sections for used water flow diversion, enabling safe maintenance access with no disruption to used water conveyance.

“The construction of the conveyance system for DTSS Phase 2 will pose a new set of exciting challenges for us, as we look forward to dig deep to navigate through a variety of ground conditions in the Jurong Formation as well as tunnel beneath existing underground infrastructure and even under the sea,” Yong Wei Hin, Director of DTSS Phase 2, PUB, said. “The DTSS is a more cost-effective and sustainable way of meeting Singapore’s used water needs and securing NEWater supply for the future than simply renewing and expanding the existing conventional used water infrastructure. PUB will continue to harness advanced technologies to enhance Singapore’s used water management system and ensure its water sustainability for the future.”