Deep Tunnel Sewerage System, Singapore

Client: Public Utilities Board Singapore
Contracts: T03, T05, T06 and various link sewers.
Main Contractors: Kumagai – SembCorp JV, Philipp Holzmann – SembCorp JV, Ed. Zublin

AKS Material Quantity Used:

T03: 94 000m2
T05: 150 000m2
T06: 96 000m2
Link Sewers: 170 000m2

The Singapore Government realised a need to plan ahead to ensure that services are well-catered for in the rapidly growing city, which has very limited space available for future above-ground development.The new trunk sewer was constructed by Tunnel Boring Machine, to a depth of up to 45m below natural ground level. The total trunk sewer length is 48.7km, apart from the lateral tunnels, link sewers, access tunnels, service and access shafts. The smallest internal diameter of main tunnel is 3.3m and the bulk of the sewer has an internal diameter of 6m.

Primary CPL Specification

2.5mm minimum thickness AKS Concrete Protection Liner manufactured of HDPE and installed to 330O of sewer internal circumference.

Turbulance in sewage aggrevates the release of sulphides – which leads to a more aggressive environment.

DTSS Contract T03

6m diameter T03 Tunnel 5.1km long.

Prefabricated sheets.

DTSS Contract T05

3.6m diameter T05 Tunnel 12.5km long.

The concrete to the invert of the tunnel is placed as a secondary operation, after the rails have been removed.

DTSS Contract T06

3.3m Diameter T06 Tunnel 9.5km long.

All extrusion welds to the internal circumference of the tunnel were carried out after the CPL had been cast into in-situ concrete. Automated “orbital welding machines” were used.