McConnell Dowell, as part of the Adelaide Aqua consortium (including Abigroup, Acciona Agua & United Utilities) are designing and constructing the Adelaide reverse osmosis seawater desalination plant to deliver 100 GL of desalinated water per annum, about half of Adelaide’s water needs.

The Adelaide Aqua solution encompasses a range of initiatives aimed at minimising operating costs, environmental impacts and energy use including:

• A pre-treatment process that provides high levels of reliability, uses less energy and reduces chemical dosing requirements;
• A highly efficient reverse osmosis design, which sets an Australian benchmark for efficiency, energy savings and physical footprint;
• An innovative diffuser for the saline concentrate that will ensure adequate mixing back into the marine environment and ensure the project meets the tough environmental performance criteria set.

The project is a massive undertaking involving all our design and construction disciplines.

Civil and Building Works
The project kicked off with over 600,000m3 of earthworks, followed by extensive services infrastructure and concrete works.

As part of the alliance, Built Environs is undertaking building works including construction of the main process building containing the reverse osmosis (RO) and filtration equipment, along with a further 12 buildings to cater for pump stations, chemical plant and administration facilities. They are also building the main visitors centre.

High performance concrete, steel coatings and roofing systems are being used throughout to cope with the challenging marine and chemical environment.

Tunnelling
MacDow’s team of tunnelling specialists quickly mobilised work crews on the construction of the three shafts, (each 60 m deep and 14 m in diameter), which were delivered on schedule in mid 2010.

Construction of the massive underground cavern to house the majority of the mechanical equipment followed. The two tunnel boring machines ('Cora the Bora' and  'Nessie') arrived from Germany and were positioned in the shafts to commence construction of the 1.4 km intake tunnel and the 1.1 km outlet tunnels.

In mid July 2010, Cora the Bora reached her target of 1.1 km in the outfall tunnel, and is now entombed at her destination. The 'Santa Fe' jack up barge was mobilised for the marine works including connection of the diffusers to the outfall tunnel. This work was completed on schedule in July 2010. As at August 2010 the intake tunnel is now 95% complete towards its target of 1.4km.

Mechanical
The MacDow mechanical team's first task was the laying of large diameter underground GRP pipe work to connect the inlet and outlet structures to the desalination plant and the ballast tanks.

The team worked hard to lay and hydrotest the pipes, so that they could be filled with water prior to the pour of the concrete building foundations by Built Environs. Filling the pipes weighs them down, preventing them from rising through the setting concrete.

Stakeholder Liaison Group
A Stakeholder Liaison Group was set up for the desalination project’s design and construction phase. This group assists the AdelaideAqua project team identify local issues related to the project, and members share information with their communities. 

The Stakeholder Liaison Group meets regularly and includes representatives from local government, business, environmental groups and the South Australian community.

Environmental Management
AdelaideAqua, the SA Government and SA Water are committed to the highest environmental standards for the project.

Critical environmental studies have been undertaken and environmental performance measures implemented for every step of the project. A comprehensive Environmental Impact Statement (EIS) was developed for the the project and was the subject of rigorous community consultation.

Operating within a sensitive marine and coastal environment at Port Stanvac on Gulf St Vincent south of Adelaide, it was imperative that the project’s marine works be undertaken in an environmentally sensitive way. AdelaideAqua’s bid was successful largely due to their commitment to safeguard the protected cliffs and near shore reef zone - choosing tunnelling to create the intake and outfall structures, rather than placing pipes on the seabed.

Dredging and pile driving activity for the intake and outfall risers was subject to compliance with the Environmental Protection Agency’s (EPA) water quality and dredging guidelines.   A determination to exceed the expectations of the client and the local community has led to a world-first innovation, which may have a number of future applications. The team designed a floating detention and sedimentation basin on a dumb barge - the Mandiri.

Dredged material is taken onto the barge into sediment tanks where the solids settle through baffles, before feeding into a secondary treatment system of filter units and flocculent dosing. The clean water is returned to the marine environment while the spoil is recycled as clean fill. This is the first time efforts have been made to this extent to ensure compliance with water quality standards on a project of this nature.

Delivery Program
First water was delivered by April 2011 (approximately 15 million litres a day), progressing to 50 GL capacity by the end August 2011 and full 100 GL capacity by the end of December 2012.

Transfer Pipeline Project
MacDow’s pipeline team, in joint venture with Built Environs, also completed the design and construction of the transfer pipeline system which links the desalination plant to Adelaide’s existing water supply.

The South Australia Water Corporation (SA Water) awarded the Adelaide Desalination Transfer Pipeline Project to McConnell Dowell Constructors (Aust) Pty Ltd in joint venture with Built Environs Pty Ltd in December 2008. This significant award is the culmination of an extensive pre-qualification and early contractor involvement (ECI) process. 

The project included the design and construction of the transfer pipeline system which links Adelaide’s new desalination plant to its existing water supply.

The scope of work included:

• 10 km of 1,575 mm diameter MSCL rising main and 2 km of 1,575 mm diameter gravity main;
• a transfer pump station with a capacity of 150 ML/day; and
• a  9 ML capacity break pressure tank, 44 metres in diameter and 6 metres high.  

The Adelaide Desalination Project will deliver up to 100 billion litres of water each year, about half of Adelaide’s water supply. The plant will deliver a climate-independent water source, ensuring drinking water is available even in times of drought.

The desalination project is a key part of the South Australian Strategic Water Initiative which will secure future water supply for the people of South Australia. 

Successful completion of pipe laying on the Adelaide Desalination Plant Transfer Pipeline project was achieved on 16 March 2010, two weeks ahead of schedule.