Sydney Metro West – Western Tunnelling Package (WTP)
At a glance
Sydney Metro West is a significant infrastructure project that will connect Greater Parramatta with the Sydney CBD, increasing rail capacity and supporting Sydney’s long-term growth.
GHD, in partnership with SMEC Australia as part of a design joint venture (DJV), was appointed lead designer for the Sydney Metro West – Western Tunnelling Package, a $2.7 billion project delivered by the Gamuda Australia and Laing O’Rourke Consortium.
Our team provided design services for nine kilometres of twin segmental-lined running tunnels between Westmead and Sydney Olympic Park, as well as supporting infrastructure such as station boxes, dive structures, and a stabling and maintenance facility at Clyde.
The challenge
The Sydney Metro West – Western Tunnelling Package involved complex underground works through some of Sydney’s most constrained urban corridors, underlain by highly variable and challenging ground conditions.
The alignment passed beneath densely developed areas, existing transport infrastructure, utilities, waterways and sensitive assets, requiring designs that carefully managed settlement, ground movement, and construction risk.
Geotechnical conditions varied significantly along the corridor, including soft alluvial soils, contaminated ground and areas of limited subsurface information, particularly at the Clyde Stabling and Maintenance Facility. Developing safe, buildable and resilient design solutions required a detailed understanding of ground behaviour and close integration of geotechnical, structural and systems engineering disciplines.
Our response
GHD brought together specialists in deep tunnelling, geotechnical engineering and systems engineering to support both the tender and delivery phases. We worked closely with our joint venture partner, the WTP contractor, and Sydney Metro. Our team remained co-located with the client throughout the tender evaluation and delivery phases, enabling real-time collaboration, rapid decision-making, and a smooth transition from tender to construction.
GHD needed to develop design solutions that balanced constructability, safety, environmental performance, and long-term operational value.
During the tender phase, the reference design continued to evolve, especially at the Clyde Stabling and Maintenance Facility. Prompt responses to changing requirements and late-stage technical requests required a collaborative approach, strong technical leadership, and the ability to adapt designs efficiently while maintaining safety and quality.
Key elements of our approach included:
- Developing robust subsurface and geotechnical models to inform tunnel, station box, and dive structure design, despite limited ground data.
- Applying our understanding of soft soil behaviour and contamination risks at Clyde to support environmental assessments and spoil management strategies.
- Leading the Systems Engineering and Safety Assurance (SESA) framework, guiding non-TAO-accredited subconsultants and ensuring compliance with Sydney Metro requirements.
- Focusing on both capital expenditure (CAPEX) and total expenditure (TOTEX) outcomes, delivering designs that support efficient construction and long-term operation and maintenance.
Through our Idea Hub, we captured, assessed and implemented innovative ways of working, helping unlock value across the project lifecycle.
What we delivered:
- Tender and construction design for the WTP running tunnels, station boxes, dive structures and the stabling and maintenance facility.
- Geotechnical modelling and interpretation to support underground works.
- Hydrology, drainage, and flood modelling for stations, service infrastructure, and maintenance facilities.
- Systems engineering leadership and safety assurance under the SESA framework.
- Construction phase services to support delivery on site.
The impact
Our collaborative, solutions-focused approach helped secure a successful tender outcome and laid a strong foundation for construction.
We delivered meaningful value for our client and the construction team, including:
- Optimising tunnel lining segment design to reduce material use and improve tunnel boring machine advance rates.
- Supporting the introduction of precast segmental lining in mined tunnels, a contractor-led innovation that expanded the use of this methodology in underground construction, including the use of a custom-designed Lining Erector Machine (LEM), developed specifically for the non-circular tunnel profile.
- Delivering a critical design solution that enabled tunnelling near a heritage sewer without diversion, avoiding significant disruption and generating major time and cost savings.
- Refining cross-passage and sump designs to minimise tunnel boring machine disruption, supporting the contractor-led use of autonomous tunnel boring machines for the first time in Australia.
- Reducing contaminated soil excavation requirements through innovative structural solutions, including an overbridge at Unwin Street.
- Improving flood resilience, safety and Crime Prevention Through Environmental Design (CPTED) outcomes across key facilities.
- Enhancing constructability through bridge solutions over waterways.
- Strengthening permanent ground support at the Parramatta metro station in response to challenging ground conditions.
- Collaboratively resolving complex design challenges and promptly adapting designs to meet evolving site information and project requirements.
Through technical excellence, collaboration and innovation, we are helping deliver critical infrastructure that will support Sydney’s growing population and transform how people move across the city.