Case Study
T2D — Torrens to
Darlington
Main South Road / Pedler Creek tender phase (2020)
Project Overview
The Torrens to Darlington (T2D) project represents the final and most complex section of Adelaide's North-South Corridor, connecting the previously completed Torrens to Torrens and Darlington Upgrade projects into a continuous non-stop motorway through metropolitan Adelaide. With an estimated project value exceeding $15 billion, T2D is South Australia's largest-ever transport infrastructure investment, featuring twin tunnels of approximately 4.5 kilometres, surface motorway connections, and multiple grade-separated interchanges.
Jerome was engaged as Tender Method Engineer by a Tier 1 joint venture consortium during the competitive tender phase, focused specifically on the bridge construction packages. This role required developing detailed construction methodologies for every bridge and elevated structure within the project scope, translating reference design information into buildable sequences with realistic programme durations and accurate cost estimates.
The bridge packages included tunnel portal structures, overpass bridges at major arterial road intersections, rail overbridges, pedestrian and cycling bridges, and retaining wall systems at the transition zones between tunnelled and surface motorway sections. Each methodology had to account for the project's unique constraints: active traffic on South Road, proximity to residential properties, interfaces with the tunnel boring and cut-and-cover works, and staging requirements that maintained access to cross-streets throughout construction.
Scope of Work
JCY delivered the following tender-phase engineering services for the bridge construction packages:
- Construction methodology development for all bridge and elevated structure packages
- Crane selection, positioning studies, and lift planning for precast and steel erection sequences
- Temporary works concept design for falsework, shoring, and construction platforms
- Traffic staging plans for bridge construction over live South Road carriageways
- Interface analysis between bridge packages and tunnel portal construction sequences
- Design review and constructability assessment of reference design bridge details
- Programme duration estimation for each bridge construction activity sequence
- Cost estimation for bridge packages including plant, labour, materials, and temporary works
- Risk assessment and contingency quantification for bridge construction activities
- Tender submission documentation including methodology narratives, programme logic, and pricing schedules
Key Challenges & Solutions
Tunnel Portal Interface
Bridge structures at tunnel portal locations had to be constructed in tight coordination with cut-and-cover tunnel works, with shared excavation zones and temporary retaining systems. The construction sequence required careful phasing to avoid clashes between bridge foundation piling and tunnel wall installation. Jerome developed integrated staging plans that defined spatial and temporal exclusion zones, sequencing bridge piling operations to complete before tunnel wall construction reached each portal zone, eliminating the risk of concurrent deep excavations within overlapping influence zones.
Live Traffic on South Road
South Road carries over 60,000 vehicles per day through the project corridor, and maintaining traffic flow during bridge construction over the existing carriageways was a hard constraint. Jerome engineered methodology solutions using incrementally launched superstructures and overnight crane lifts of precast elements, minimising the duration of lane closures. Each bridge methodology included detailed night-work staging plans with specific crane pad locations, exclusion zone dimensions, and traffic control requirements approved by DIT.
Competitive Cost Accuracy
In a competitive tender environment, bridge package cost estimates had to be aggressive enough to win while remaining deliverable. Jerome drew on first-hand construction experience from T2T and Gateway South to build estimates from actual productivity rates rather than reference book allowances. Temporary works costs were estimated using specific falsework configurations rather than percentage-based allowances, and crane costs reflected actual mobilisation and utilisation patterns from comparable Adelaide projects. This approach produced pricing with substantially tighter contingency margins than industry-standard estimation.
Technical Details
Structure Types
- Tunnel portal transition structures
- Grade-separated interchange bridges
- Rail overbridges across active corridors
- Pedestrian and cycling bridges
- Retaining wall systems at cut-to-tunnel transitions
Deliverables
- Construction methodology narratives for each bridge package
- Crane lift study reports with load charts and reach diagrams
- Programme logic networks with activity durations
- Bridge package cost estimates with breakdown structure
- Risk register with quantified contingency recommendations
Project Partners
Related Services
Project Gallery
On-the-ground photography from this project.
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JCY brings hands-on bridge construction experience to the tender phase, delivering methodologies grounded in real-world productivity and constructability.