Twentyfirst Street Bridge, SA
Client:
Renmark Paringa Council and BMD Constructions
Location:
Renmark, SA
Project value: $6.5 Million
After sustaining significant damage during the 2022/2023 River Murray Flooding event, the original load limited Twentyfirst Street Bridge was closed to the public for safety reasons.
What we did
Tonkin provided end to end professional planning and engineering services for the Twentyfirst Street Bridge Recovery through various client engagements to both Renmark Paringa Council and BMD Constructions.
Tonkin was engaged by Renmark Paringa Council to provide planning and options development for the bridge recovery effort, including development of up to 6 long-list options, through to refinement and selection through a multi-criteria assessment process. The options development phase also included engagement with the Department of Environment and Water to understand recent and historic flooding impacts in the Renmark reaches of the Murray River floodplain and incorporate the latest regional hydrology model into the bridge development solution.
Tonkin also provided short-term access and loading assessments for the old bridge structure to reinstate access to pedestrians while the new design was finalised. This was a key community outcome noting the proximity of schools to the project site and the direct connection to residential areas in Renmark West.
Tonkin then went on to become the lead consulting design engineers for the new bridge during the design and construct phase, partnering with BMD Constructions.
Our locally based Riverland Team ensured the new structure was delivered to the highest standard and built to withstand future flooding events and serve the community for decades to come. As both lead designers and community members, our team took pride in designing a structure that would benefit the region for years to come.
Tonkin was engaged by Renmark Paringa Council to provide planning and options development for the bridge recovery effort, including development of up to 6 long-list options, through to refinement and selection through a multi-criteria assessment process. The options development phase also included engagement with the Department of Environment and Water to understand recent and historic flooding impacts in the Renmark reaches of the Murray River floodplain and incorporate the latest regional hydrology model into the bridge development solution.
Tonkin also provided short-term access and loading assessments for the old bridge structure to reinstate access to pedestrians while the new design was finalised. This was a key community outcome noting the proximity of schools to the project site and the direct connection to residential areas in Renmark West.
Tonkin then went on to become the lead consulting design engineers for the new bridge during the design and construct phase, partnering with BMD Constructions.
Our locally based Riverland Team ensured the new structure was delivered to the highest standard and built to withstand future flooding events and serve the community for decades to come. As both lead designers and community members, our team took pride in designing a structure that would benefit the region for years to come.
How we made a difference
The multidisciplinary project team comprised Tonkin’s skilled engineering and technical experts who provided a single point of contact throughout all stages of the project, ensuring a seamless client experience.
Tonkin was able to support the project from initial disaster response works to options studies and planning, advanced river system hydrology and hydraulic modelling, detailed design and documentation, as well as construction phase support.
Tonkin’s in-depth knowledge of the local area, as well as technical expertise and prior experience working with Renmark Paringa Council and BMD Constructions, ensured that our team could easily navigate challenges and draw upon valuable insights to deliver the project efficiently and effectively.
With specialist capability in hydrology and hydraulics, transport structures, road design and our strong local presence, Tonkin was uniquely positioned to lead the design management of the Twentyfirst Street Bridge, achieving an exceptional outcome for both the project and the community.
Tonkin was able to support the project from initial disaster response works to options studies and planning, advanced river system hydrology and hydraulic modelling, detailed design and documentation, as well as construction phase support.
Tonkin’s in-depth knowledge of the local area, as well as technical expertise and prior experience working with Renmark Paringa Council and BMD Constructions, ensured that our team could easily navigate challenges and draw upon valuable insights to deliver the project efficiently and effectively.
With specialist capability in hydrology and hydraulics, transport structures, road design and our strong local presence, Tonkin was uniquely positioned to lead the design management of the Twentyfirst Street Bridge, achieving an exceptional outcome for both the project and the community.
Innovations
Early design assessments during the option development phase identified key long-lead items which needed to be addressed early to support project program objectives.
Tonkin was able to identify overhead power relocations and native vegetation approvals, which needed to be completed prior to works commencing. With early identification, these were taken off the critical path and removed construction constraints, significantly benefitting the construction program.
To maximise benefits to the creek floodplain and eco-system, new high-flow culvert structures had been identified within the project extents, to ensure environmental flows have access pathways to all reaches of Bookmark Creek. In the event of higher flows and future flooding, the primary bridge spans and high-flow culverts will distribute water, reducing peak velocities at key points and reducing the potential for erosion around bridge foundations.
The road environment design was also developed with local environment and flooding resilience in mind. Earthworks batters were designed at flatter grades to manage peak velocities and scour impacts in overtopping events, and barrier extents were kept to a minimum to reduce flow obstructions. Sealed or stabilised granular pavements were used in shoulder to ensure that the primary road pavement would have sufficient support under all conditions.
Tonkin was able to identify overhead power relocations and native vegetation approvals, which needed to be completed prior to works commencing. With early identification, these were taken off the critical path and removed construction constraints, significantly benefitting the construction program.
To maximise benefits to the creek floodplain and eco-system, new high-flow culvert structures had been identified within the project extents, to ensure environmental flows have access pathways to all reaches of Bookmark Creek. In the event of higher flows and future flooding, the primary bridge spans and high-flow culverts will distribute water, reducing peak velocities at key points and reducing the potential for erosion around bridge foundations.
The road environment design was also developed with local environment and flooding resilience in mind. Earthworks batters were designed at flatter grades to manage peak velocities and scour impacts in overtopping events, and barrier extents were kept to a minimum to reduce flow obstructions. Sealed or stabilised granular pavements were used in shoulder to ensure that the primary road pavement would have sufficient support under all conditions.
What we achieved
It was important that the bridge did not undergo a ‘quick fix’ and that the bridge would serve as a long-term solution which would be safe and resilient well into the future.
Through detailed and thorough planning, Tonkin assisted Council in selecting a recommended reconstruction option which balanced the objectives of flood immunity and flood resilience, local area impact, community need and cost.
The all-new structure combines a separated active transport pathway, on road bike lanes and two-way vehicle access with unrestricted load limits, allowing all community stakeholders to cross safely and maximise access routes for local industry and agriculture.
The new Twentyfirst Street Bridge was formally opened to the public with an event in May 2025 - inviting community members to walk across the structure before welcoming unrestricted traffic.
Through detailed and thorough planning, Tonkin assisted Council in selecting a recommended reconstruction option which balanced the objectives of flood immunity and flood resilience, local area impact, community need and cost.
The all-new structure combines a separated active transport pathway, on road bike lanes and two-way vehicle access with unrestricted load limits, allowing all community stakeholders to cross safely and maximise access routes for local industry and agriculture.
The new Twentyfirst Street Bridge was formally opened to the public with an event in May 2025 - inviting community members to walk across the structure before welcoming unrestricted traffic.
"The Twenty First Street Bridge Replacement project was a true example of successful collaboration on a design and construct project between Renmark Paringa Council, Tonkin, and BMD Constructions. Tonkin’s expertise in structural engineering and flood resilience, paired with their proactive and professional project management support during construction, was instrumental in delivering a high-quality outcome. Their detailed assessments, including Level 3 Bridge Inspections and flow modelling, provided a solid foundation for supportive Council to make informed decisions throughout the project.
The strong partnership between all parties ensured open communication, efficient problem-solving, and a shared commitment to building back better. Tonkin’s support and experience helped guide the project smoothly from planning through to completion, ensuring the bridge now stands ready to serve the community for years to come."
The strong partnership between all parties ensured open communication, efficient problem-solving, and a shared commitment to building back better. Tonkin’s support and experience helped guide the project smoothly from planning through to completion, ensuring the bridge now stands ready to serve the community for years to come."
- Shannon Baxter, Renmark Paringa Council