Years of drought across much of Australia led to record low water storage levels in 2008, particularly in Queensland, where the state government is investing some $4.5 billion in water infrastructure to protect itself from future droughts.
Halcrow’s design and technical skills have played a key part in the construction of a desalination plant for the Gold Coast. The first on the eastern seaboard, the plant is part of a multi-million dollar initiative between the state government and the Gold Coast City Council.
The project comprises a reverse osmosis desalination plant, 1.5km marine intake and outlet tunnels, and a pipeline to connect the plant to the south-east Queensland water grid. Commissioned by the Gold Coast Desalination Alliance, Halcrow produced detailed designs for the shafts, tunnels and marine seabed risers – used to collect seawater and disperse brine.
The Halcrow-designed tunnel lining features steel-fibre, reinforced-concrete segments – a material not widely used in Australia – enabling durability while optimising the lining thickness. Halcrow provided invaluable guidance during the manufacturing process, providing client and contractor with information on the benefits of this approach.
The team investigated several design options for the intake tunnels and outfall shafts to reduce the effect of construction on the environment and local communities, with tunnelling selected as the least harmful to the environment. Halcrow’s design team revised the geotechnical data and reference design for tunnel and shafts, identifying significant cost savings.
The connection between the tunnels and the seabed was designed by Halcrow, taking into account the high level of risk of flooding when making the connection and the clients requirement to be able to seal and dewater the system at any time.
As James Garnier, Halcrow’s project manager, explains: “The plant’s location – in a residential area boasting pristine surfing beaches – meant it was essential that the intake tunnels and outfall shafts were constructed with minimal impact to the environment and the community. Other options, involving ‘open trenching’ or excavation from ground level, would have had a significant impact on the surrounding areas. Additionally, the greater likelihood of damage to the pristine Tugun beach during construction made other options unacceptable.”
The Desalination plant will provide a secure water supply to the area. The tunnels and marine risers ensured there was minimal disruption to the world famous Gold Coast Surfers Paradise beaches. Design features allowed the construction techniques in the marine field to avoid any environmental issues with excavation to make connections to the tunnels.