The Western Sydney International (Nancy-Bird Walton) Airport (WSA) project is a rare greenfield opportunity for a new airport rather than a reconstruction or renovation of an existing airport. It is also one of the largest civil earthmoving projects in Australia’s history.
The airport will open in late 2026 and is projected to serve up to 10 million domestic and international passengers annually. The overall design of the terminal and airport property brings together best practices to offer passengers and airlines an experience unrivalled among Australian airports.
Major earthworks commenced on the project in 2020 and involves moving around 25 million cubic metres (32.7 million cubic yards) of earth to support the construction of the major elements of the airport including the 3.7 km (2.3 mile) runway and the passenger terminal. The earthworks has been conducted in stages, allowing for handover of areas to other contracts to support the construction of the runway and terminal by late 2026.
Other distinctive features of the project’s scale, area and volume include:
- 470 ha (1,161 acres) topsoil stripping and stockpiling for later reuse in the landscaping phase.
- 7.3 million square meters (8.7 million square yards) of landscaping.
- 7,000 lineal metres (4.3 miles) of trunk drainage.
- Construction of four permanent flood detention and bioretention basins with capacity to control 1:100-year average recurrence interval (ARI) events. These basins have capacity between 48.1–131 megalitres (12.7 million to 34.6 million gallons) each (Figure 1).
- 134 potential archaeological sites that required investigation and salvage prior to commencement of construction. The scale of the archaeological program required a team of 138 Aboriginal site officers to assist the project’s archaeologists to investigate and salvage the 134 areas over a period of 12 months. The salvage operation involved wet sieving procedures with 100% recycled water that was not discharged to the environment.
- 507 threatened plants that were relocated into the airport’s environmental conservation zone prior to construction commencing.
Located on the east coast of Australia, the airport is approximately 41km (25.4 miles) west of Sydney central business district. On average, the area receives a median rainfall of 651.8 mm, with an average of 69.1 days of rain. Since commencement in 2020, the project has been subjected to two consecutive years of La Niña conditions. This has resulted in much greater than average rainfall, with over 1,000 mm of rain received each year, including to date in 2022. This excessive rainfall, accompanied by challenges with COVID-19 has exasperated the risks and challenges involved with such a large-scale project, such as impacts to construction schedule and maintaining compliance with both state and federal regulations. Innovative and dynamic tools and processes to effectively manage the risks involved include:
- Design and establishment of 16 temporary basins to prevent sedimentation in the surrounding waterways and to protect aquatic life. These basins have the capacity to retain over 400 megalitres (over 160 million gallons) of water.
- Sediment basin treatment procedures and dewatering logistics to handle the vast quantities of water collected.
- Sustainable management of silt reuse from basins.
- Around 99% of water used for construction purposes, including dust suppression, has been obtained from recycled sources and without relying on groundwater, abstraction from rivers or potable water sources. Recycled sources included reuse of water captured during rainfall as well as off site locations.
The biggest environmental challenge the construction team faced was the large-scale management of erosion and sediment control in a landscape that was quickly changing as earthworks progressed (Figure 2). With approximately 25 million cubic metres (32.7 cubic yards) of material to be moved at a rate of approximately one million cubic metres (1.3 million cubic yards) every month, the project’s landform and catchments changed at a significant rate (Figure 3). The earthworks program involved the site transitioning from 16 catchments to five over a period of approximately 24 months. For the project to be a success it was critical to have appropriately sized sediment basins in place for every catchment at every stage. This required careful planning of sediment basin sizes, positions and catchment diversions to ensure water run-off from rain events could be appropriately controlled at all times.
One of the key tools the joint venture environment team developed to monitor erosion and sediment control planning compliance was the monthly basin and catchment aerial surveys. Changes in catchments were predicted and forecasted where possible, however due to the dynamic nature of bulk earthworks and different geological conditions encountered it was important for the project team to establish a monthly reporting procedure to self-audit compliance with the site’s erosion control design standards.
The basin aerial reporting process is conducted with these key steps:
Step 1: Monthly aerial LiDAR surveys.
Drones and manned aircraft are used to take aerial LiDAR surveys of the entire site. Due to the size of basin catchments, ground-based surveys are not practical. Catchments average 54 ha (133 acres) but could be up to 327 ha (808 acres).
Step 2: LiDAR data conversion to user friendly GIS platform.
The LiDAR data collected during the surveys is converted to contour and watershed data which is then uploaded onto the project web-based GIS platform. The GIS platform enables all team members to easily access, view and interpret the data.
Step 3: Catchment mapping via GIS review.
Catchments are manually mapped to ensure sub surface drainage structures and pre-rain diversion drainage controls that would not be picked up by the survey data are considered.
Step 4: Monthly basin volume checks.
Basin volumes are resurveyed monthly to confirm volumes have not been impacted by sediment accumulation or interactions with permanent design features.
Step 5: Data review and recalculation of basin volumes.
Data from steps 3 and 4 and other checks are made to update basin calculations.
Step 6: Earthworks forecast review.
Forward planning with the construction teams for catchment management is also undertaken. This planning allows careful and considered staging to take place to ensure ongoing compliance with volume requirements.
Step 7: Transparent reporting.
A basin compliance report is prepared based upon the above data and is issued to WSA for transparency each month. This transparency enhances the confidence and relationship between the joint venture partners and the airport.
The reporting procedure has resulted in the early identification of risks that the earthworks team were facing such as catchments amalgamating. When identified, to avoid basins failing and maintaining compliance, these risks were mitigated by methods such as raising dam walls, major catchment diversions or early commissioning and temporarily retrofitting operational flood detention basins as sediment basins.
The procedures implemented have proven successful, as no rain events have resulted with basin capacities exceeding the basin design criteria.
This process has shown that it is vital that the erosion and sediment control industry is aware of, and takes advantage of, advancements in technology, particularly survey and drone, to secure the best environmental outcomes.
About the Experts
John Wiggers de Vries, CPB ACCIONA Joint Venture, is the environment and sustainability manager for the Western Sydney Airport Bulk Earthworks package. He has been in the construction industry for 11 years on large scale infrastructure projects, ensuring projects are delivered in a sustainable and environmentally compliant way while optimizing construction efficiencies.
Melanie Kleine, CPB ACCIONA Joint Venture, an environmental professional passionate about sustainable futures in both the natural and built environment. She is an environmental coordinator for the Western Sydney Airport Bulk Earthworks package and has played a key role in erosion and sediment control management on the project.
About the Project
The civil earthmoving project for Western Sydney International (Nancy-Bird Walton) Airport is being delivering by the CPB Contractors (a member of CIMIC Group) and ACCIONA Joint Venture on behalf of Western Sydney Airport.