PUB breaks ground for conveyance system of Deep Tunnel Sewerage System Phase 2

PUB, Singapore’s national water agency, held a groundbreaking ceremony for the enhanced conveyance system of the Deep Tunnel Sewerage System (DTSS) Phase 2 to mark the start of construction works on 20 November 2017. Officiated by guest of honour, Minister for the Environment and Water Resources, Masagos Zulkifli, the ceremony was held at the site of DTSS Phase 2’s first tunnelling shaft at Penjuru Rd.

The deep tunnels in Phase 2 will connect to the existing deep tunnels in Phase 1 serving the eastern part of Singapore and the public sewer network to create one seamless integrated system. The whole of Singapore will be served by the DTSS when Phase 2 is complete by 2025. 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 is discharged into the sea.

Constructing DTSS Phase 2
To be built using the tunnelling method, this massive 100-kilometre 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 inlet shafts within the future Tuas Water Reclamation Plant. Nineteen Tunnel Boring Machines will be used to dig at depths of between 35 to 55 metres below ground and under the sea to create 40 kilometres of deep tunnels and 10 kilometres of link sewers. The remaining 50 kilometres 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 100 years 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. 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,” said Yong Wei Hin, Director of DTSS Phase 2, PUB. — Construction+ Online