Koombooloomba Dam Bridge
HumeDeck™ modular solution delivers a sensitive upgrade in a World Heritage environment
Background
The existing single-lane timber girder bridge crossing the Tully River at Koombooloomba Dam had reached the end of its service life. Any replacement solution needed to respond carefully to its environmentally sensitive setting within a World Heritage listed area, while also making use of the existing bridge substructure.
Humes was engaged to deliver a solution that would minimise environmental disturbance, reduce on-site construction activities, and enable a fast, precise installation.
Key Challenge
The project presented a combination of structural and environmental constraints, including:
- Reuse of the existing bridge piers and substructure
- Variations in pier heights across the span
- Raising the bridge deck and adjoining road approaches
- Incorporating fall in the deck units to allow for drainage
- Minimising site works and impact on the surrounding river environment
Humes Solution
Humes supplied a HumeDeck™ modular bridge system, purpose-designed for installation on existing substructures or as a complete precast bridge solution. Key features of the delivery included:
- No in-situ concrete pouring, significantly reducing environmental impact and site logistics
- One-piece deck and girder units, allowing rapid installation and reduced site work
- Use of an on-site gantry system, constructed on the existing bridge, to remove old timber girders and install the new deck units
- Installation of two spans in a single day, minimising disruption
- A custom headstock design developed by Humes to accommodate varying pier heights and ensure precise alignment
Precision manufacturing ensured the finished surface level of all headstocks was within a 3 mm tolerance once installed.
Innovation and outcome
The completed 91-metre bridge now spans the Tully River just downstream of Koombooloomba Dam, delivering a durable, low-maintenance solution aligned with the site’s environmental and operational requirements.
HumeDeck™ units are designed in accordance with AS 5100 and suitable for a wide range of load regimes, including W80, A160 and SM1600. The system can be produced in spans from 6 to 12 metres and widths up to 2.7 metres, offering flexibility for future bridge upgrades across Australia.
The project demonstrates how modular precast bridge solutions can successfully balance structural performance, construction efficiency and environmental sensitivity.
