Waikato Expressway - Huntly Bypass

The highly challenging, steep and narrow site confines and the surrounding biodiverse terrestrial and wetland areas and streams called for an innovative design approach. The team developed alternative induced trench design to manage stormwater flows and meet the extensive ecological mitigation measures set out by key stakeholders. The induced trenching design uses compressible polystyrene in the trench above the pipe to effectively “unload” the embankment weight from the pipe and shed it instead into the surrounding ground.

River bridges were extended in length (compared to the conceptual design) in order to span the entire river reach, which provided both cost savings in ground treatment avoidance within the river floodplain and better outcomes for the local iwi (people) and the environment.

The team’s collaborative approach to the preparation of the environmental management plan, extensive ecological enhancement and restoration, outstanding visual and landscape outcomes, and substantial carbon emissions savings, demonstrate a commitment to achieving sustainable value for the client, community, local iwi and all stakeholders.

The team implemented a "Safety in Design" approach, bringing together people from across the project team to assess whole of life safety risks of the project which were then either eliminated or mitigated through the design process. They also adopted a "Value Plus" philosophy whereby design elements were interrogated at each design stage in the pursuit of true value. Together, these approaches helped to deliver a safer design concept with reductions in project costs of over $6.5 million (NZ $10 million).

The sustainable outcomes achieved on the Huntly Section have delivered a legacy that will be enjoyed by generations to come.