The Umbagong District Park Pedestrian Bridges won the small projects (under $10 million) category at the 2023 Steel Sustainability Awards. The project oversaw the replacement of existing timber walking bridges in favour of more secure steel alternatives.
The original timber walkway was constructed in 1986. Since then, it has become one of the ACT’s most serene spaces for recreational activity and wildlife. However, a safety audit found the existing timber bridges were not fit for purpose.
ACT Steelworks—the only fabricator servicing the ACT to be SSA certified—led the project alongside architect TCL; engineer Sellick Consultants; and head contractor Complex Co.
The project manager from ACT Steelworks James White said the team worked harmoniously to navigate some of the project’s constructability challenges. “This was crucial to ensure minimal environmental impact and develop a safe method of work.”
The bridges were designed to have a minimal impact on the local environment, both during the construction process and for the lifetime of the structures. Designers used the existing bridges as a guide for the location of their steel replacements. Meanwhile, engineers capitalised on the natural rock outcrops as structural foundations. This saved on the number of new materials entering the environment.
“A very low impact solution that truly capitalises on the ACT inland exposure classification and opportunities to touch the ground very lightly.” ~ Judges
The three bridges were designed to be wider than their original counterparts to improve access for pedestrians, cyclists, and increase accessibility for mobility scooters and wheelchairs. In addition, the larger bridge incorporates a new lookout area and seating.
“An efficient design was paramount to ensure the safety and wellbeing of the community could be maintained,” White said.
The design team developed smaller steel member sizes into typical and recurring modules, which allowed manual handling of all components. This eliminated the need for haul roads, crane pads and heavy machinery.
All steel used in this project was procured through InfraBuild Steel, who optimised efficiencies in the materials while ordering. The team also reused the existing timber bridge components to create new seating throughout the park. Meanwhile, the offcuts of steel plates were used as a plaque for each of the seats.
All other wastage was separated into appropriate material types for offsite recycling.
Corrosion protection for the bracing included hot dip galvanizing, while the support columns were painted in a PUR7 system offsite at an industrial coatings specialist, Dean Industrial. This protection is durable for 25 years to first maintenance.
“This steel design would far outperform the timber design and with a rusted steel appearance blending in with the surrounding native environment, the pedestrian bridges will retain their appearance for decades to come without the need for maintenance,” White said.
The rusted finish of the bridges was designed to complement the natural setting and colours of the Umbagong grasslands. The rusted finish was achieved offsite by lightly abrasive blasting the fabricated assemblies prior to the application of three even mist coats of a 1:10 Ferric Chloride to water mix. Shortly after, the assemblies were rinsed with water to neutralise the coating.
“The Umbagong District Park Pedestrian Bridges project was one all stakeholders can be proud of,” White said.
Project team
- Entering Organisation: ACT Steelworks
- Architect: T.C.L.
- Engineer: Sellick Consultants
- Head Contractor: Complex Co.
- Steel Fabricator: ACT Steelworks
