Project Description

Singapore's Deep Tunnel Sewerage System (DTSS), when fully completed, will replace the existing sewerage system which dates back to 1960. DTSS will consist of two large bore, deep tunnels that criss-cross the island, two water reclamation plants and two deep-sea effluent pipelines, together representing a total investment of around $ 7 billion.

Some 100 km of tunnels, with diameters of up to 6.5 m, will be constructed at depths between 20 m and 60 m, and will carry sewage and waste water by gravity to the reclamation plants at Changi and Tuas, both built on reclaimed land. The benefits to Singapore will include maximising the reutilization of water, enhanced operational reliability of the sewerage system, and the reuse of land for higher value developments by phasing out the existing treatment plants.

Sited near Changi airport and designed to handle 800'000 cubic metres of waste water per day, the Changi Water Reclamation Plant Phase 1 (CWRP) will receive raw sewage, as well as treated effluent from the existing outdated plants, at 60 m below ground level.

After preliminary treatment in the excavation works, the sewage passes through primary sedimentation tanks, before flowing into bioreactors, which break down the impurities and organic matter, and then into secondary sedimentation tanks. The treated effluent is finally pumped through 5 km long outfall pipes into the sea, where it is diluted and dispersed 30 m below the surface. The residual high solids material in the sedimentation tanks, known as sludge, is screw pumped to aerobic digesters for additional biological breakdown, before being sent to large centrifuges for the final dewatering and reclamation.

Project Requirements

Straub Werke AG, Switzerland, was awarded the contract to join together these major steel pipes with their connection system designed specifically for this purpose.
The sewage pipes were made of steel and were up to 4 metres in diameter. The ends of the pipes could not be aligned precisely enough for standard pipe connection systems and they were not perfectly circular at the ends once installed.
To make the pipe connections so that they were level, and so that their long term integrity could be assured even under pressure, both of these deviations had to be compensated for.

Sika Solutions

To achieve the necessary alignment of the pipe ends with each other, and to compensate for the shape, it was decided to apply a band of Sikadur®-30 (2 part epoxy adhesive mortar) around the whole of the perimeter of the steel pipe, onto which the pipe connection could then be fitted. The layer thickness of the Sikadur®-30 had to be carefully adjusted on each section of the pipes circumference to match the deviation of the pipes to be connected.
Level jointing and correct installation of the pipe connections could then be achieved.

Tests at Straub Werke AG:
Preliminary tests were carried out by Straub in Switzerland. Sikadur®-30 was applied on a steel pipe with a much smaller diameter and the connection was installed after it had cured. Leak tests were then carried out at the design water pressure. A test with the same diameter pipe as for the project (approx. 4 m), was then carried out by Straub in Toronto, Canada.

Sika Products

In addition the following Sika product was used in the project

  • Sikadur®-30

Check out more information about the Sikadur®-30 product in the Singapore market

Project Participants

Owner: Changi Water Reclamation Plant (CWRP) Singapore
SubContractor Connection Assemblies: Straub Werke AG Wangs, Switzerland
Applicator Sika Products in Site: Kongsberg Technology (S) Pte Ltd, Singapore