Wonthaggi Desalination Plant, Victoria, Australia

Wonthaggi Desalination Plant will be the largest in Australia once it is completed in 2011. The $3.5bn plant, also called the Victorian Desalination Project, is being constructed on the Bass Coast near Wonthaggi city in Victoria.

Construction was started in September 2009 after the acquisition of cleared farmland behind the coastal dunes near Wonthaggi.  Apart from the plant, a buffer zone will be built on the acquired land. Neither construction nor operation of the plant is expected to cause any significant harm to the native vegetation and coastal habitat.

Opposition to the plant

Public rallies and protests were taken out against the project throughout 2007, 2008 and 2009. A petition signed by nearly 3,000 people opposing the project was submitted to the Victorian Parliament in 2009.

The government is being accused of privatising the water resources as the plant is being built under public-private partnership (PPP). The protesters claim residents will have to pay nearly $900m a year for the desalination plant and the water produced from it.

Australian Greens, the third largest political party in the country, and several community groups have opposed the plant. The government was legally pursued by a community group, Your Water Your Say. The group, however, lost the legal battle and was asked by the government to compensate for the legal costs.

Key players

The Victorian Government awarded the project contract to AquaSure consortium, which consists of Degrémont, Macquarie Capital, and Thiess, in June 2009.

The consortium is responsible for financing, designing and building the plant.

It will also operate and maintain the plant for 30 years (including the construction period).

In November 2009, a contract of $43m was awarded to Olex for supplying high-voltage alternating current power cabling.

Thiess has also awarded a contract of $7m to Ortech Industries for the manufacture and supply of 44,000m² of its 'Durra Panel' acoustic ceiling system and 38,000m² of roof system. The company has awarded another sub-contract of $6m to Ausform to build water retaining structures.

In October 2010, Thiess Degremont awarded a contract to Siemens Automation to supply process automation and switchgear equipment for the plant. Siemens will supply PCS7 equipment which is used to manage the flow, vibration, temperature and pressure.

Fytogreen was awarded a $4.3m contract by Thiess Degremont in September 2010 to install about 98,000 indigenous ground covers, shrubs and tussocks over a roof area covering more than 26,000m².

Gippsland Building Approvals will undertake property surveys, Atco will supply site amenity buildings, Pro-rent will construct a truck wheel wash and additional site amenity buildings, Safeman Australia will supply personal protective equipment, Douglas Partners will undertake geotechnical investigations and Dandenong's Alfasi Design and Drafting provided 3D modelling of the project. DHL Global Forwarding, which is the logistics partner for the desalination project, will deliver nearly 60,000t of material and equipment during the construction.

Victoria's water supply

In the past ten years, Victoria has experienced several water crises, higher temperatures and record low rainfall. As a result there has been a significant reduction in the availability of water.

In order to improve Victoria's water supply, the Government announced the Our Water, Our Future plan in June 2007. The Wonthaggi seawater reverse osmosis desalination plant is intended as a long-term solution to secure Melbourne's water supply.

Wonthaggi desalination project

The Wonthaggi Desalination Plant project has four main components. In the first component, the plant will be constructed with a capacity to generate 150-200 gigalitres a year.

The second component involves establishment of a link between the plant and offshore constructions located in the Bass Strait by building two 0.8km to 2km long tunnels. The first tunnel will be used to supply seawater to the plant, and the second to move saline concentrate, discharged from the plant. 

In the third component, water will be transferred to Melbourne's water supply system by laying an underground pipeline from Wonthaggi to Berwick.

The fourth and final component facilitates the plant's operations by supplying 90mW to 100mW of electricity. 

Desalination plant design and construction

Thiess Degrémont was responsible for both designing and constructing the Wonthaggi Desalination Plant.

The plant works include the construction of a reverse osmosis desalination process plant, 84km long water transfer pipeline, marine tunnels and structures, and 87km underground power-lines to supply the plant with energy.

The soil excavated for the plant will be used to construct a series of new dunes. The 170m x 170m reverse osmosis building foundation works and piling works for the pre-treatment area are also being carried out. In order to construct the seawater lift pump station, a 27m deep box-cut has been made to provide access to the tunnel boring machinery.

ipelines have been laid for 84km near Berwick to transfer desalinated water to Melbourne and regional water networks. The pipeline, which will be capable of supplying up to 150 billion litres of drinking water per year, is made up of nearly 6,200 pipe sections, each having a diameter of 1.93m, a length of 13.5m and weighing 13t.

Work on the 1.5km long outlet tunnel that will be used to discharge saline concentrate from the plant in the Bass Strait was commenced in September 2010. Work on this outlet tunnel was finished in March 2011 with the help of a Tunnel Boring Machine (TBM) named Rocking Ruby.

The 1.2km long intake tunnel was completed in December 2010. Boring was undertaken by Wonthaggi Maggie TBM. To help protect marine environments, intake and outlet tunnels of the plant are being built 15m-20m beneath the sand dunes and seabed.

The twin tunnels were constructed using 10,700 concrete segments. In the next stage of works, the two tunnels will be connected to the marine structures on the seabed. Installation of drilling risers into the seabed, and the intake and outlet structures on the seabed has been completed.

Wonthaggi plant sustainability

The completed plant will operate on 100% renewable energy.

One of the main features of the plant's design is a living green roof, the largest of its kind in Australia. The roof, which is made up of biodegradable materials, will be used to camouflage the plant. It will provide thermal control, corrosion resistance, acoustic protection and reduce the need of maintenance.

Utmost care has been taken to keep the building's footprint small; it is being developed in only 38 hectares of the 263 hectare site.

The remaining area will be used to develop an ecologically sustainable landscape.

Provision has also been made to create paths for local cyclists, pedestrians and horse riders.

The indigenous vegetation on the plant site, which has been cleared to make way for construction, will be restored by the planting of over three million plants and shrubs.

In order to integrate the plant with adjacent landforms, and minimise visual and noise impact, the site will see the reconstruction of coastal dunes.

Desalination treatment

The seawater is first supplied to the desalination plant through an intake system. Fine particles are removed through an initial screening of the seawater. The seawater is then made to pass through a pre-treatment system to filter the finer particles.

Reverse osmosis membranes are used to desalinate the seawater. The desalinated water is further treated to meet the Australian Drinking Water Guidelines and Victoria Government health requirements.