Case Study
DIT SA Regional Bridge
Renewal Projects
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Onkaparinga Valley Road bridge replacement (2023)
Project Overview
South Australia's regional bridge network spans thousands of kilometres of rural highways, connecting agricultural communities, freight corridors, and critical service routes across the Adelaide Hills, Horrocks Highway, and Princes Highway. Many of these structures date from the mid-twentieth century and face escalating deterioration from heavy vehicle loading, flood events, and decades of deferred maintenance.
Working within the Department for Infrastructure and Transport's Bridge & Marine Infrastructure Delivery Team, Jerome operated as both Bridge Engineer and Project Manager across a rolling programme of bridge condition assessments, replacement design coordination, and culvert renewals. The programme covered more than 30 structures in various states of serviceability, from minor concrete spalling through to full structural replacement requirements.
JCY's contribution focused on developing standardised assessment methodologies, coordinating replacement designs with internal and external engineering teams, and managing procurement and delivery of priority renewal works. Key structures included the Aldgate Creek Bridge, multiple bridges on the Balhannah corridor, and aging timber and concrete structures along the Onkaparinga Valley Road alignment.
Scope of Work
JCY delivered the following services as part of DIT's ongoing regional bridge renewal programme:
- Level 2 and Level 3 bridge condition assessments in accordance with DIT inspection standards
- Structural capacity assessments and load rating calculations for aging timber, steel, and reinforced concrete bridges
- Replacement design coordination with DIT's in-house design team and external consultants
- Culvert replacement design and construction oversight for undersized or failed drainage structures
- Development of standardised assessment and reporting methodologies adopted across the programme
- Prioritisation framework development, ranking structures by structural risk, traffic volume, and freight route significance
- Construction staging and traffic management planning for rural highway bridge replacements
- Procurement support, tender evaluation, and contractor coordination for renewal packages
- Post-construction inspections and defect liability period management
- Coordination with local councils and emergency services for temporary bridge closures and load limits
Key Challenges & Solutions
Aging Timber Substructures
Several bridges on the Onkaparinga Valley Road featured original timber piles and headstocks with advanced internal decay not visible during surface inspection. Standard visual assessments understated the structural risk. JCY implemented targeted resistograph testing and core sampling to accurately map internal deterioration, allowing DIT to prioritise emergency load restrictions on the three most critical structures while replacement designs were fast-tracked.
Flood-Prone Construction Windows
Multiple sites in the Adelaide Hills and Horrocks Highway corridor are subject to flash flooding during winter months, creating extremely narrow construction windows for in-stream works. JCY developed phased staging plans that sequenced all in-water activities within the October to March dry season, with pre-fabricated components delivered to site ready for rapid installation. This approach compressed wet-weather-sensitive activities by 40 percent compared to conventional sequencing.
Rural Traffic Management
Regional bridge sites presented unique traffic management challenges: single-carriageway roads with no viable detour routes, heavy vehicle access requirements for grain harvest periods, and limited sight distances on winding hill roads. JCY coordinated with local councils, SA Police, and freight operators to develop staged construction plans that maintained single-lane alternating traffic flow at all times, with full closures limited to overnight periods during low-traffic seasons.
Technical Details
Key Structures
- Aldgate Creek Bridge - reinforced concrete deck replacement
- Balhannah corridor bridges - timber-to-concrete upgrades
- Onkaparinga Valley Road structures - emergency load assessments
- Horrocks Highway culverts - hydraulic capacity upgrades
- Princes Highway bridge abutment repairs
Deliverables
- Level 2 and Level 3 inspection reports with photographic records
- Structural capacity rating calculations (AS 5100 compliance)
- Prioritised renewal programme across three highway corridors
- Standardised assessment methodology templates for DIT adoption
- Tender documentation and contractor evaluation reports
Project Partners
Project Gallery
On-the-ground photography from this project.
Need a Similar Capability on Your Next Project?
JCY delivers bridge condition assessment, replacement coordination, and construction management for government asset owners and Tier 1 contractors throughout South Australia.