How early engagement is delivering exemplary low carbon outcomes at a Sydney project

At Laing O’Rourke, sustainability is not just a goal, it’s a strategic imperative embedded in how we plan, design, and deliver infrastructure. In Greater Western Sydney, the St Marys Station footbridge project is demonstrating how early engagement, technical innovation, and persistent collaboration can deliver measurable carbon reductions, well before the first concrete pour.

Transport for NSW (Transport) in partnership with Laing O’Rourke is delivering a new footbridge and northern plaza at St Marys Station as part of the Sydney Metro -Western Sydney Airport project. From the start, the team set out to challenge conventional approaches and explore what was technically possible, aiming to create an exemplar for the use of low carbon materials in infrastructure.

A bold idea takes root

In 2022, Laing O’Rourke proposed a bold idea to Transport to deliver a low carbon materials-led project. The concept was embraced, and Transport encouraged us to challenge the norm and push the boundaries of what was possible in a future project.

This early alignment laid the foundation for a collaborative journey that began to take shape the following year, when the company was awarded the St Marys Station footbridge contract. Laing O’Rourke’s Technology and Innovation team began working closely with Transport for NSW and our design partner Arcadis to develop a preliminary emissions profile and map carbon hotspots across the design, pinpointing where the greatest gains could be made. The analysis confirmed that prioritising the use of low carbon materials would have the greatest potential for overall emissions reduction.

Designing and procuring with a sustainability goal

While waiting for construction to begin, the team focused on influencing sustainability outcomes during the design stage. Through months of technical reviews and supplier engagement, Laing O’Rourke identified very low carbon concrete mixes in the market that met the project’s technical specifications. Once suitable mixes were identified and validated with our design partner Arcadis, Laing O’Rourke encouraged suppliers to submit them for inclusion in Transport’s Concrete Mix Register. This enabled their use not only on the St Marys project but also opened the door for their adoption on other infrastructure projects across New South Wales. A tide that would lift all boats.

The team also pursued the use of lower carbon concrete mixes already approved for higher exposure classes for use in lower exposure class applications on the project, offering another pathway to reduce embodied carbon. Arcadis validated these options, and Transport approved their use, further demonstrating the power of early collaboration.

In parallel, Laing O’Rourke recommended the use of InfraBuild SENSE600 reinforcement steel to build the footbridge headstock and deck, a high-strength alternative new in the market that reduces material volume without compromising performance. The product has 27 per cent less CO₂ than standard Australian 500N reinforcement steel. This was integrated into the design, further lowering the project’s carbon footprint.

As the project moved into the building stage in 2024, the team continued to pursue sustainability gains through procurement. One standout example is the sourcing of NatSteel reinforcement, a low carbon product from Singapore, supplied locally by Bestbar Reinforcements, for in-situ work, including raft slab, columns, lift pits, escalator pits and footings. This product has 60 per cent less CO₂ than standard Australian reinforcement steel. This decision reflects how our projects can leverage their purchasing power to drive further decarbonisation outcomes during the building stage.

This combined approach during the design and the building stages – which involves identifying suitable low carbon materials, validating them with design partners, and securing client approval – has become a blueprint for how Laing O’Rourke delivers on its sustainability ambitions in Australia.

Exceeding expectations

As a result of Laing O’Rourke’s low carbon concrete and steel initiatives, the St Marys Station footbridge project is currently tracking significantly above its overall emissions reduction targets. According to Laing O’Rourke’s most recent Sustainable Design Guidelines (SDG) Rating Submission, the project is currently on track to exceed the contractual target of a 25 per cent reduction in greenhouse gas emissions.

Although the St Marys Station footbridge project commenced before Laing O’Rourke’s Concrete Carbon Limits policy came into effect, the team voluntarily tracked its concrete performance against the company’s emissions standards. The results are striking: 95 per cent of the concrete used to date on the project meets Laing O’Rourke’s Low Carbon Concrete definition, including 100 per cent of the 50MPa concrete and 93 per cent of the 40MPa concrete. At the same time, all the concrete used on the project comfortably meets Laing O’Rourke’s maximum tolerance for carbon emissions.

While data for precast elements is still being finalised – and may reflect higher emissions due to technical constraints – the current results underscore the impact of clear focus, early planning and sustained effort.

A model for future projects

The St Marys Station footbridge is more than a piece of transport infrastructure. It demonstrates how sustainability can be embedded from the earliest stages of a project through design and supply chain collaboration, challenging the norm for a greater outcome, and procurement strategy.

This approach reflects Laing O’Rourke’s broader commitment to reducing whole life carbon, improving the lives of people while preserving the health of the planet. As Laing O’Rourke continues to drive greater sustainability outcomes across our projects, the lessons learned from St Marys Station offer a clear example of how early engagement and targeted action can shape a lasting legacy.