Queensland’s far north will soon have a substantial component of its power needs met by the Mt Emerald Wind Farm.
Work is well underway on a construction project that will supply as much as a third of Far North Queensland’s power needs when complete.
The $380 million Mt Emerald Wind Farm, situated approximately 50km south-west of Cairns on a 2400Ha greenfield site, will incorporate 53 wind turbines capable of generating 180.5 MW of power.
Wind Farm developer Ratch Australia estimates that the wind farm will power 75,000–90,000 homes in Far North Queensland and inject close to $70 million directly into the regional economy.
The Mt Emerald site was chosen for its orientation and elevation, both of which are conducive to strong and consistent power generation. But the site offers other advantages. Few residences are located near the site and its proximity to the electricity grid means the length of the transmission line can be reduced. Environmental impact studies also concluded that there would be minimal environmental and social harm caused by its location.
The enormous rotors will dominate the plateau adjacent to the Mt Emerald area once all 53 towers are erected. Thirty-seven (3.45MW) Vestas turbines will sit atop 90m towers, each with a 117m-diameter rotor; and another 16 (3.3MW) Vestas turbines will sit atop 84m towers with 112m-diameter rotors. Each of the blades weighs a massive 16 tonnes.
By project end, approximately 40km of new site roads will also be have been constructed in order to deliver the turbines to site safely and to connect the turbines.
Bombs and bent bar
Ensuring a steady supply of steel product to the Mt Emerald site was key to getting the foundation work complete, with InfraBuild Construction Solutions (formerly LIBERTY OneSteel Reinforcing) partnering with engineering firm Catcon to supply and deliver 2250 tonnes of reinforcing bar for the wind turbine footings.
Michael Jostsons, Project Manager for InfraBuild Construction Solutions, said a coordinated program was put in place utilising the company’s Cairns, Townsville and Acacia Ridge branches to ensure the supply of the 600–700 tonnes of bar per month required by the project. The program was critical in allowing the Cairns branch to continue to service its new and existing customers.
InfraBuild Construction Solutions partnered with engineering firm Catcon to supply 2250 tonnes of reinforcing bar for the wind turbine footings
A deal was also struck with logistics firm TOLL to provide off-site storage at rail yards in Cairns and Townsville so there was no disruption to supply.
Among the challenges associated with the project, the rugged terrain of the site and difficulties associated with access to the footing locations were two that could be foreseen and accounted for.
However, another challenge must have come as some surprise. With that region of Queensland’s Atherton Tableland once a World War II mortar training facility, there existed the very unusual problem of there being unexploded ordnance in the area. Specialised metal detection equipment was used to the detect the presence of mortar and hand grenade fragments and risk mitigation strategies had to be put in place in order for work to proceed.
The threat of untimely explosions aside, Catcon was keen to ensure not just efficient scheduling, but that materials were manufactured within strict tolerances.
The tower design requires that an 800-tonne concrete and steel foundation act as an immovable anchor to withstand the extreme forces acting on each tower. Each base must also be capable of supporting the 120-tonne nacelle (the shipping container-shaped box housing the generating components) that forms the hub of the wind turbine.
To meet the requirements of the structure, a 43-tonne reinforced steel cage was used and filled with approximately 350m3 of concrete. Over 300 tonnes of steel stirrups had to be bent manually and supplied to the site, which Michael explains was no small feat.
“The stirrups are basically massive bars of 28mm and 32mm diameter that were bent into shape to work as a spacer,” he said. “They’re awkward to bend, heavy and difficult to transport.”
In addition, 94 tonnes of radius bars were manufactured, again to tight tolerances, and delivered to the site.
Once the concrete was poured, it was then left to cure to maximum strength (a process that took around four weeks) before the foundation was backfilled with rock and soil to match the natural surface level. With the foundations in place, work is now underway to bolt the bottom section of each tower to the concrete-and-steel flooring with the use of 168 36mm bolts.
Construction work began at the Mt Emerald Wind Farm site in February 2017, with the contract to supply reinforcing bar to Catcon coming to an end in February 2018. The towers are now midway through the erection process, with the aim to complete two towers per week until the end of August in time for an expected completion date of October 2018.
The success of the foundation work was the result of many hours put towards the project, Michael said. He added that regular consultations with the steel fixers, project coordinator, site managers and production teams were important for understanding the critical requirements of the project and delivering on the customer’s expectations.
Long days and tight deadlines were commonplace during the project. “The dedication of all staff and contractors involved in managing, scheduling, producing and delivering on this project was plain to see,” he said.
Michael singled out Project Coordinator Andrew Bourne for his role in scheduling supply for the tower footings. “Andrew’s ability to communicate with the customer to understand their needs and implement requests from the steel fixers to fine-tune supply were a key factor in InfraBuild Construction Solutions’ success with this project.”
Meeting the demands of the Mt Emerald project has borne fruit with InfraBuild Construction Solutions subsequently winning the supply contract for another wind farm project. From April 2018 it will supply approximately 6000 tonnes of reinforcing bar for the construction of 123 turbines at the Coopers Gap wind farm west of Toowoomba.
Completed wind farm tower image courtesy of Ratch Australia
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