The Gold Coast Desalination Alliance (GCDA) provides engineering services for the establishment of a 125 mega litre reverse osmosis seawater desalination plant for the production of potable water at Tugun on the Gold Coast. The Gold Coast Desalination Project is the first large scale water desalination plant on Australia’s eastern seaboard.

Tunnelling operations

Winslow said that their microtunnelling operator has over twenty years experience in the tunnelling industry, and has used the mts system for the past seven years in Australia and Asia.

The mts 2000 Perforator working in conjunction with the Schauenburg separation unit has surpassed all specification tolerances, coming in on the target shafts within 10 mm either side of the line and level.

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The Bemuda Street land crossing, Currumbin Creek crossing and the Tallerbudgera Creek crossing tunnels have been constructed using Humes ‘J’ series 1,500 mm ID concrete jacking pipes. The ‘J’ series were chosen due to the extra designed strength, and the ground conditions encountered.

Bemuda Street land crossing

The 140 m drive was completed in eighteen days, allowing a cutter head change at approximately 90 m. The excavation through hard basalt to a depth of 15 m ensured that tunnelling was the most viable option for the crossing. Currumbin Creek crossing

The ground conditions encountered were medium strength sandstone with soft clays and estuarine mud. The 270 m drive, 3 m under the Currumbin Creek bed, was completed in fourteen days.

Tallerbudgera Creek crossing

The Tallerbudgera Creek crossing bored 3 m under the creek. The drive was 170 m in length and was completed in six days. Boring on the crossing achieved a production rate of up to 45 m in a 24 hour shift, excavating nearly 2 m per hour.

Completion

All shaft design & construction, tunnelling works, water main and riser installation and subsequent backfill of shafts was completed by Winslow Infrastructure.

The company said that once the concrete enveloper pipe had been tunnelled a MSCL water carrier pipe was inserted and tested. Winslow handed over to the GCDA a finished product ready to use.