Kopu Bridge - Replacement

Replacement

In addition to the constrained traffic over the bridge (with flows projected to increase by 2% per year over the next 15 years), investigations in 2001 had also found that the bridge was likely to be severely damaged or might even collapse in an earthquake stronger than that of a 300-500 year return period, and that it had failed to pass safety inspections which require the ability to withstand a 2,500 year return period quake. In 2006, Transit New Zealand announced their intention to build a second bridge slightly upstream of the existing bridge and to route the State Highway over the new bridge. The start date was at that time set for no earlier than 2011, but this was later brought forward to late 2009.

The new bridge is 587 m long, and has 16 spans, with its foundations being driven 36 m to 50 m deep into the riverbed, due to the soft swampy ground not providing good support otherwise. Much of the ground would also have to be forcibly compacted first. The design incorporates images of waka and taniwha, and landscaping using native plants. The cost was originally estimated at $32 million but this later rose to $47–48 million (including 2.5 km of new approach road as well as a new roundabout near Thames).

The bridge's navigation channel at the central span will be 42.8 m wide and 6.5 m above mean sea level, allowing larger vessels to pass under it, without the need for a swing bridge as for the old structure.

In late 2011, it was announced that the bridge would be ready in time for the December 2011 holiday traffic despite earlier reports that completion was still likely to be in mid-2012.

Due to its historical significance, the existing bridge will be retained and upgraded, possibly to be integrated into a new cycleway along the coast - though the new bridge will also provide access to cyclists and walkers.