The work and the technique: Perth Airport Line,
The three Redcliffe, Airport Central and High Wycombe stations can be found along the 8.5-kilometre route of Perth new Airport Line. The entire line construction that includes a double-barrel tunnel and three new stops, was appointed, in April 2016, to a consortium led by Salini Impregilo, now Webuild, with the participation of NRW Pty Ltd, and with the involvement of a supply chain of over 1,200 companies.
Two TBMs were specifically designed for tunnel excavation activities, which began in July 2017. The TBMs have a diameter of over 7 metres and belong to the Variable Density type, which are used when there are unstable excavation front conditions, featured by the presence of pressurized work environments. The work's construction featured a challenging context, due to the soil's hydro-geological conditions, the path running under the airport's lanes, of the functioning railway lines and the riverbed of the Swan River, where excavations needed to reach up to 26 metres in depth.
The entire line was designed and constructed with very high sustainability standards, in terms of the technology, materials and construction models used. Due to the location's water scarcity, the two TBMs worked with a system equipped with special filters that can reuse the water after treating it. The water saved at the end of the works was calculated to be 2,740 mega-litres, the equivalent of more than 1,000 Olympic swimming pools.
Particular attention was placed on materials. In fact, concrete was produced with a special cement mix made by 655 of recycled alternative materials. This allowed to greatly reduce the amount of cement used (over 350 kg per cubic metre of concrete) and also to consequently reduce toxic emissions into the environment by almost 22,000 tonnes of CO2.
The slates supporting the tracks were also built with a special reinforced concrete mix, made of synthetic microfibres instead of steel, with an overall steel reduction of 7 million kg, with a further saving of toxic emissions of over 13,000 tonnes of CO2. Another fundamental aspect was studying the energy supply of the stations. A solar system with 626 solar panels was installed on the roof of High Wycombe station. During the summer, this system can supply all the energy needed by all three stations of the line.