Mandurah Estuary Bridge Duplication: design and loading insights for engineers
Reviewed by Joe Ashwell
First reported on Roads & Infrastructure (AU)
30 Second Briefing
The $148.8 million Mandurah Estuary Bridge Duplication has opened its new westbound carriageway to traffic, easing pressure on the existing bridge that currently carries more than 33,000 vehicles per day between southern Mandurah and the city centre. The project adds a parallel structure across the estuary, effectively doubling lane capacity on this key north–south coastal route in Western Australia. Remaining works will focus on completing the eastbound duplication, tie-ins and approach road upgrades, which will influence future traffic loading, maintenance access and estuary-side geotechnical performance.
Technical Brief
- Staging the opening allows demolition, strengthening or resurfacing works on the existing bridge under reduced live load.
- Traffic management now focuses on temporary tie-ins and lane shifts at each abutment during eastbound construction.
- Construction sequencing must maintain estuary navigation clearances and minimise in-water works while the parallel span is completed.
- Load redistribution between old and new structures will inform future inspection intervals and maintenance strategies for the original bridge.
- Approach road upgrades will need revised pavement design to reflect higher cumulative ESAs and changed braking/acceleration patterns.
- Environmental controls remain critical, with duplication works occurring directly over tidal estuary waters and sensitive foreshore.
- Similar duplication schemes on constrained river crossings in WA can adopt this staged opening model to manage traffic risk.
Our Take
Within our 618 Infrastructure stories, Western Australia features heavily for coastal and estuarine crossings, signalling that assets like the Mandurah Estuary Bridge are being prioritised for resilience against sea-level rise and storm surge rather than just congestion relief.
A project cost in the order of $148.8 million places the Mandurah Estuary Bridge Duplication in the mid-range of WA transport upgrades in our database, which typically means complex staging and traffic management but still manageable for state-led procurement without large private consortia.
For southern Mandurah, duplicating a key estuary crossing often precedes or accompanies adjacent land development and densification, so local councils and utilities will likely face follow-on pressure to upgrade connecting road, drainage and services infrastructure over the next planning cycles.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
Related Articles
Related Industries & Products
Construction
Quality control software for construction companies with material testing, batch tracking, and compliance management.
Mining
Geotechnical software solutions for mining operations including CMRR analysis, hydrogeological testing, and data management.
QCDB-io
Comprehensive quality control database for manufacturing, tunnelling, and civil construction with UCS testing, PSD analysis, and grout mix design management.