The Western Harbour Tunnel is a major transport infrastructure project comprising approximately 6.5 kilometres of dual three-lane tunnels. The tunnel alignment extends from the Waringah Freeway in North Sydney, beneath Sydney Harbour, to the WestConnex interchange at Rozelle.
Package 2 of the project involves the construction of approximately 4.5 kilometres of tunnels from Birchgrove, beneath Sydney Harbour, to North Sydney. The package also includes surface works at the North Sydney portal, completion of civil fit-out for the P1 tunnel section, and mechanical and electrical fit-out along the full tunnel length.
Witt Consulting has provided ongoing geotechnical, structural, and temporary works design support throughout the delivery of Package 2. Our involvement spans early works through to detailed design and construction support.
Scope of Services
Witt’s continued involvement with this project includes design advice and engineering services across a broad range of project components, including design of tunnel launch seals, assessment of wharf load capacity and structural stability, Temporary Works design & verification, and Geotechnical & Structural engineering support.
Specific design contributions include:
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Temporary support systems for tunnel boring machine (TBM) components
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Formwork, falsework, and temporary access ramps
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Sheet piling and retaining wall systems
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Ground improvement measures
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Crane working platforms and load assessments
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Slope stability assessments
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Load capacity assessment of a heritage seawall
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Review and assessment of lattice structures
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Design of service support brackets within the tunnel
The project presented complex engineering challenges due to its marine environment, proximity to heritage assets, constrained construction zones, and the integration of permanent works with extensive temporary works. The interface between tunnelling operations, surface infrastructure, and existing assets required robust, adaptable, and construction-ready design solutions.
Outcomes
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Safe and efficient delivery of tunnelling and surface works
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Optimised temporary works designs supporting complex construction staging
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Protection of heritage and marine assets through detailed load and stability assessments
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Integrated geotechnical and structural solutions across the full tunnel alignment
Witt Consulting’s broad technical capability and continued involvement enabled responsive and practical design solutions across all project stages. By supporting both major structural elements and detailed temporary works, Witt Consulting contributed to safe construction, reduced risk, and efficient delivery of one of Australia’s most significant transport infrastructure projects.
