Client name: HEB Construction / NZ Transport Agency

Duration: November 2009 – December 2011 

Location: Coromandel Peninsula, New Zealand

Coffey proposed and implemented ground solutions to successfully replace the Kopu Bridge – resulting in improved capacity and a reduction in traffic delays in the Coromandel area.

Building a 580m two-lane bridge on a 100m deep alluvial flood plain 

SH25 is the preferred link between Auckland and the Coromandel Peninsula. Strategically important to the National State Highway Network, it carries a high volume of visitor traffic, and is an essential link for emergency services.

The historic one-lane steel and concrete bridge was increasingly unable to cope with traffic flow during holiday periods, causing traffic congestion and sizeable delays for motorists.

Construction of a new, 580m two lane bridge was funded under the New Zealand Government’s Jobs and Growth plan. The new bridge would be wider, and accommodate vehicle, cycle and pedestrian traffic. Safety, earthquake and structural standards had to be met, in addition to allowing boat traffic to navigate underneath.

HEB Construction required us to quickly develop suitable ground solutions for the construction of the new bridge on an alluvial flood plain - with more than 100m depth of variable alluvium.

Remote and continuous geotechnical instrumentation monitoring technologies

The bridge construction had to be completed in tight timeframes, and in challenging soft ground conditions.  

We facilitated the construction of pier caps and designed temporary works and piled staging running parallel to the new bridge. We were then able to support 100 tonne crawler cranes and loads, allowing a faster construction rate.

Remote and continuous geotechnical instrumentation monitoring technologies were introduced to optimise filling operations. This included the use of geotechnical instrumentation beneath the bridge approach fill embankments. This allowed us to monitor the progress of the consolidation process and pore water pressure rises, to ensure threshold levels were not exceeded. We minimised engineering risk and could confidently work more quickly.

Piles supporting the bridge were driven 55m below the Waihou River to meet load capacity standards – achieving structural and health and safety requirements for the NZ Transport Agency.

Project delivered 5 month early 

Our implementation of innovative technology allowed us to successfully deliver this project five months ahead of schedule.

The replacement of the Kopu Bridge has decreased traffic congestion in peak times, provided easier access to local businesses and improved travel times.