A JV between troubled Philipp Holzmann and SembCorp Construction has won a US$83m contract to build a 12.6km tunnel as part of Singapore’s Deep Tunnel Sewerage System (DTSS).
The contract is the first of six to be awarded for the 36.5km system, which involves the construction of a network of tunnels running from Changi East to the Kranji Sewage Treatment Works.
The contract calls for construction of the 12.6km Kranji Tunnel, the longest tunnel in the system; and ten 30m deep access shafts. According to an official of SembCorp, the 4.5m diameter tunnel will be excavated using two TBMs working mainly through granite and decomposed granite.
Spoil will be removed from the tunnel face using screw conveyors and muck trains from the TBMs to the marshalling area. The spoil will then be taken to the surface using a vertical conveyor system.
Apart from design and equipment procurement, the contractor expects to spend the first year on sinking the shafts, which include work shafts, drop shafts and access shafts designed as part of the sewerage system. These and a marshalling yard for the TBMs will be excavated by drill+blast.
Tunnelling will start in the second year and is expected to take 18-24 months. A precast segmental concrete lining will be installed in the final year of construction. The finished diameter of the tunnel will be 3.6m.
The project is scheduled for completion in early 2004.
