The $5.5 million tunnelling project took 6 months to complete, the incident-free achievement of which has helped progress the Western Pipeline Alliance’s aim of creating the largest recycled water scheme of its kind in the Southern Hemisphere.

The Western Pipeline Alliance consists of McConnell Dowell, Abigroup and GHD, and is constructing the pipeline between Bundamba and Caboonbah to supply recycled water to Tarong Power Station and Wivenhoe Dam to supplement drinking supplies. The project is an important part of the Queensland Government’s $9 billion South East Queensland Water Grid – the largest urban drought response in Australia.

The project is an integral component of the continuing upgrade of Queensland’s water system and Winslow Infrastructure was able to provide a turn-key solution. The works started with the excavation of the shaft, and finished with Winslow Infrastructure handing the WPA a fully operational mild steel concrete lined (MSCL) product pipe, including grouting of the annulus of tunnel and backfilling of the shaft. The Melbourne-based company, established over 22 years ago, has previously inserted pipes into pre-bored tunnels, but had never previously undertaken the entire process. No difficulties were encountered during the project, and practical completion was achieved on 8 March.

The Bremer River tunnel is the only major river crossing involved in the WCRWP project. The 175 m pipe installed under the Bremer River is part of the 80.4 km pipeline between Ipswich and Wivenhoe Dam. The launch shaft for the tunnelling process measured 25 m deep and the target shaft was 28 m deep.

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Winslow Infrastructure used Humes J-Series jacking pipes for the concrete shafts. An mts 2000 perforator – a closed-face slurry tunnel boring machine (MTS) with its own separator unit – was used to bore the tunnel, after which 175 m of mild steel cement-lined water carrier pipes of 1.5 m internal diameter was laid underneath the river.

While the sandstone and mudstone terrain proved a challenging environment, the Winslow team did not have any difficulty in efficiently completing the work.

The tunnelling began before Christmas last year and took 14 days to complete. Between 10 and 15 workers were active 24 hours/day, rostered in two 12 hour shifts.

In addition, Winslow had been involved in intensive risk management workshops with the WPA to ensure the safest possible working environment while constructing the Bremer River crossing. No work safety issues were encountered during the procedure, which was completed on schedule and to the great satisfaction of all involved.

The efficiency and excellence of Winslow’s work in tunnelling under the river was integral to the successful delivery of the project which, when complete, will be the largest recycled water scheme of its kind to be constructed in Australia.