City West Cable Tunnel
- Passes within a few metres of major city office towers and infrastructure, including the Cross City Tunnel
- A tunnel lining was designed that ensures the integrity of every structure in the CWCT zone of influence
- Features include automated lights and ventilation fans that operate on an engineer’s arrival to the tunnel and shut off when exiting
- The first tunnel project in Australia to be driven by 100 per cent accredited GreenPower
- Approximately 45,600 tonnes of sandstone spoil was excavated during construction with 100% of the spoil excavated beneficially reused
The City West Cable Tunnel (CWCT) is an example of how sustainable design can reduce long-term maintenance costs and increase the working life of a significant piece of infrastructure. The cable tunnel solution for client Energy Australia eliminated major disruption to the city’s CBD by providing an alternative to the traditional ‘pit and trench’ method, which would have required extensive excavation in busy city streets.
Passing below Sydney’s CBD, the 1.6km long CWCT carries 132kV electricity transmission feeder cables from TransGrid’s bulk supply point to the new City North Substation. This substation is designed to supply up to one quarter of the city’s future electricity requirements.
Construction involved the use of a 3.75 metre diameter TBM for 1.62km of tunnel and a roadheader for excavation of 100 metres. The tunnel varies from about 25 metres to 45 metres deep, with a maximum gradient of 3 per cent for the TBM sections, which allowed efficient spoil removal. Excavation was primarily through Sydney Sandstone, but also passed through the Pittman Dyke and the Great Sydney Dyke, comprising very hard igneous material.
The $54 million project is relatively unique among hard-ground cable tunnels in that it is a segment-lined tunnel rather than shotcrete lining and groundwater drains. We took responsibility for the design of the precast concrete segments, as well as analysis and monitoring of any settlement.
Conservative estimates demonstrate the additional cost of lining the tunnel will be recovered within seven years through reduced maintenance.
This commitment to sustainable excellence was carried across every facet of the project. Initiatives including water recycling and the use of 100 per cent GreenPower for construction has seen the CWCT become a world class example of how major tunnelling projects can reduce their environmental impact.
