SH39 Mangaotama Stream Bridge Replacement

Client

Waka Kotahi NZ Transport Agency

Scope

Bridges
Roading
Complex Structures
Pavement and surfacing

Partners

Beca
This project involved the full replacement of a single-span steel girder concrete-deck bridge on SH39 within a 14-day road closure. The new structure was prefabricated offsite in two sections, transported to site, and installed with a high-strength concrete stitch connection.

Works included backfilling, shoulder widening, barrier upgrades, and repositioning fibre optic services. Careful planning and material movement coordination were essential, as the removal of the old bridge meant a 20-minute detour to access opposite abutments.

Operating over a live waterway required strict environmental controls, including erosion and sediment management, vacuum extraction for concrete slurry, and spill prevention protocols. The team also identified and resolved road alignment errors just before reopening, working closely with designers and contractors to deliver a last-minute pavement solution. 3D modelling and digital planning ensured accurate positioning of bridge components, while a detailed 15-minute interval closure programme enabled a highly efficient workflow.

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