The recent awarding of the Airfield Works contract to Skyway, a joint venture of BMD Construction Pty Ltd and CPB Contractors Pty Limited (a member of the CIMIC Group), marks the start of the final phase of 3.3km parallel runway at Brisbane Airport that will be operational in 2020, and meets Brisbane Airport’s projected capacity needs to 2050 and beyond.
BMD had earlier involvement in the runway project in 2012-13, having been the early enabling civil works contractor for the first phase of the project, which included site clearing and access provision, construction of site compounds and provision of a 1.7km floodway and other significant drainage works.
The underlying ground conditions of soft, waterlogged mud and silt up to 35m deep required significant improvement to provide the stable, level surface necessary to support the runway. Ground consolidation is being achieved by surcharging, and is accelerated by driving 330,000 vertical wick drains into the ground – the largest such installation in Australia.
The variability of ground conditions meant that surcharging levels vary across the site. Some areas will settle more than 2m. More than 1000 ground plates monitor the consolidation. Some areas have been stripped of surcharging material while, in other areas, this is not expected to occur until 2018-19. The stripped material is being moved to adjoining areas, where it will be used for future aviation infrastructure. Around 4.5 million cubic metres will be stripped.
The new ground level flood proofs the runway and provides immunity from rising sea level projections from climate change, as well as providing seamless integration with existing runway and taxiway infrastructure.
International dredging specialist Jan de Nul (Australia) used its Charles Darwin trailer suction hopper dredge to extract 11 million cubic metres of marine sand from Middle Banks in Moreton Bay. Environmental considerations were paramount during this work. The dredged sand was pumped to site from a temporary mooring site on the Brisbane River through a 1.1m diameter pipeline that, at its longest, stretched 8.5km. Pumping avoided significant truck movements.
For pumping, water was mixed 5:1 with sand, requiring construction of bund and tailwater ponds to allow settlement before the pump water was released into the Kedron Brook floodway via the new major drainage system.
The dredge worked around the clock, averaging three round trips per day and delivering 30,000 cubic metres at a time. The dredging work was completed in 2014, ahead of schedule.
Hall Contracting completed seawall and site access works in 2016-17. This provided construction access to the new runway site from Moreton Drive, and replacement of an existing dumped rock wall with a 1720m engineered seawall protecting the airport foreshore.
McConnell Dowell is undertaking the Dryandra Road Works, which includes a four-lane underpass and 1.1km of separated roadway, providing access between the north and south of the link taxiways for both airside and landside traffic. The underpass structure will be supported on 700 precast concrete piles. Work is scheduled for completion in mid-2018.
The Airfield Works contract involves construction of a 3.3km long, 60m wide runway and up to 12km of 25m wide taxiway pavement, as well as airfield infrastructure. Concrete and asphalt batch plants are being established on site, and about 1.25 million tonnes of quarry material will be brought to site and processed through a crushing and screening plant.
This article was originally published in the inaugural issue of Inside Construction.