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Leighton Holdings Quarterly Update 2nd Quarter 14 underground brine outlet tunnel underground inlet tunnel underground fresh water pipe pumping station pumps drum screen residuals area 15Ml tank 15Ml tank flocculation tanks filter beds reverse osmosis building Gold Coast Desalination Project now over 50 percent complete The John Holland Group is part of the GCD Alliance, which was awarded a contract to construct, operate and maintain the Gold Coast Desalination Project in December 2005. The GCD Alliance is comprised of John Holland, Veolia Water, Sinclair Knight Merz and Cardno, and is delivering the project on behalf of SureSmartWater - a 50/50 joint venture between Queensland State Government and Gold Coast City Council. John Pincock, Project Director of the Gold Coast Desalination Project, talks about it's operation and progress. "The Gold Coast Desalination Plant is a project capable of delivering 125 megalitres per day ensuring the future water supply of South East Queensland. The project is on schedule to supply first water in November 2008 and full water capacity in January 2009. "John Holland is the principal contractor in the alliance, Veolia provides the process technology, SKM provides the detailed main plant design and Cardno provides the detailed pipeline design. "The project is located at Tugun, on a 6ha site, on the coast of South East Queensland. The site was chosen specifically because of its proximity to both the ocean and also to the existing water pipework infrastructure. We commenced the project in August 2006 with remediation of the site which was an ex-waste disposal area. "In order to proceed with the project we carried out a full Environmentally Relevant Activity Application, involving numerous plans and studies by various universities to ensure that the impact of the project on the environment is minimal. "The project is comprised of three main components. The first of these are the two tunnels, an inlet tunnel and an outlet tunnel, one 2.4km long and the other 2.2km and both are nearing completion. The second component is our 24km pipeline, which is currently at about 9km laid, and is scheduled to take water around about mid-June this year. The final component and the heart of the project is the desalination plant, which is around 60% complete. "The two tunnels we are constructing are about 3m in diameter. In order to get the job completed on time we acquired two Herrenknecht tunnel boring machines, manufactured in Germany. Once we are finished with the machines they are buried out under the sea bed as we are unable to retract them from the tunnels that they have formed. "In order to get 100 year durability for the concrete inlet and outlet tunnels, our segment liners have metal fibres in the concrete instead of the standard metal reinforcing. This hasn't been done for this application before in Australia, although it has been done in Europe with great success. "The desalination process is really quite simple. We take water in from the sea, using a gravity fed system, through the intake tunnel which is 20m
Leighton Holdings Quarterly Update 2nd Quarter 15 filtered sea water tank below the surface of the sea. It then comes into the site through a shaft which is approximately 70m below ground level. On top of that shaft we have a number of pumps which pump the sea water through a preliminary intake drum screen before it reaches the flocculation tank. There we add a flocculent aid which causes fine suspended particles in the sea water to aggregate before the water goes through a number of filter beds. The filters are very similar to swimming pool filters, using sand and anthracite as a filter medium. "We then hold that filtered sea water in a tank before pumping it into the reverse osmosis building. There we have a number of modules carrying reverse osmosis membranes (which are very fine membranes.) The water is pumped through at a relatively high pressure of 64 bar and there the salt is trapped in the membranes. Because the processed water is so pure, we have to add minerals to make it taste like tap water. The water comes out from the membranes into two large 15Ml tanks. When we backwash the filters, instead of pumping that backwash out to sea we put it through the residuals area where it forms into sludge and we take it to landfill. "In order to get the water from the plant out to the distribution network for the public, it goes through a pumping station, then via a one metre diameter cement lined pipe which is buried underground. This pipeline will be laid through a number of easements and roads. Once we have gone through these areas, we reinstate them and revegetate them. "Of the water that comes into the plant only one third of it actually goes out as pure water. The other two thirds, which is brine, is twice as salty as the water that's coming in and this is pumped back into the discharge shaft and then by gravity goes back out to sea. When it goes back out to sea, in an area of about 120m by 225m, the water mixes in with the sea water and returns to normal salinity levels. This is due to the wave and tidal movements and to the design of our distribution system on the sea bed which also has minimal effect on the marine micro organisms that live in the sand. "Site safety has been a first priority for us. It has been a magnificent feat for the alliance to reach 1.75 million man-hours without a lost time injury. This has taken a lot of commitment and hard work from the team. Our motto is that if it doesn't feel safe, if it doesn't look safe, then we don't do it. "Working at heights is a major risk here. We ensure that everybody is thoroughly trained to work at heights. We also have barge work in over 20m deep water and tunnelling work under pressure, which is why we have a hyperbaric chamber on site. Because we are such a compact site, one of the other important safety issues is pedestrian and vehicular interaction. We are constantly evolving the layout of the site as the project progresses and at our pre-starts we make a point of advising everybody of any changes to crane movements and to road access changes. "Another challenge is that we are located in a heavily populated part of South East Queensland. At the start of our project all access to the site was through Boyd Street which goes through a residential area and in order to minimise the effect on the community we built our own access road to take all construction traffic away from Boyd Street. Our interaction with the community has been carried off in an exemplary manner with their full support," said Mr Pincock.
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