Perth’s new rail service, which comes into service this year, is the latest example of how the way a project is built counts as much as the contribution it makes to sustainable development.
The METRONET Forrestfield-Airport Link, to be renamed the Airport Line, will connect the city’s eastern suburbs with the airport and the business district by spurring off the existing Midland Line near Bayswater Station and running to High Wycombe.
It is 8.5 kilometres long, eight of which underground, with three stations dotting the line.
By providing an alternative to vehicle travel between the eastern suburbs and the city centre, the line is expected to carry 20,000 passengers a day. This means it will remove an equivalent of up to 15,000 vehicles from the roads every day, easing congestion and reducing CO2 emissions by up to 2,000 tonnes every year.
Sustainable concrete for the Forrestfield-Airport Link construction site
The line’s builders, Italian civil engineering group Webuild and a local partner, adopted measures to make their construction of it as sustainable as possible. One area of focus was the concrete, the most important material of any construction site. Webuild worked closely with a local supplier to develop two sustainable concrete blends, one of which was for the production of the segments that line the tunnel walls. Known as Triple Blend 60MPa Concrete, it is a low-cement concrete blend containing 65% Supplementary Cementitious Materials, such as Ground-Granulated Blast-furnace Slag, which is itself a recycled material. This blend had only 195 kilograms of cement per cubic metre of concrete, compared with more than 550 kilograms in typical 60Mpa Concrete. By using this blend rather than the concrete made with Portland Cement – which requires a lot of energy to produce – a total of 21,848 tonnes of CO2 emissions were avoided in the production of the 54,000 tunnel segments that line the walls of a combined total of 15 kilometres of tunnels.
For the production of track slabs on which the rails are positioned along the Airport Line, the builders resorted to concrete reinforced with macro synthetic fibres rather than steel. This helped avoid the use of 6.96 million kilograms of steel, preventing about 13,224 tonnes of CO2 being emitted during production.
Other measures included tunnel-boring methods and the use of solar power.
The tunnel-boring machines (TBMs) excavating the tunnels reused the water needed to function by having a plant use a filter press and centrifuge to process the slurry that they generated, separating the spoil from the water. The plant then sent the water back to the TBMs. This saved 2,740 megalitres of water, the equivalent of more than 1,000 Olympic-sized swimming pools.
Overall, recycling practices reduced water usage during all phases of the line’s construction by nearly 30%.
As for the use of solar power, one of the line’s three stations, High Wycombe, has the largest solar panel system to be installed by a state government department in Western Australia. The 275kW system is sufficient to meet the average summertime daylight electricity demand of Airport Central Station and Redcliffe Station, in addition to the High Wycombe Station where the system is installed.