State Highway 25A Taparahi between Kōpū and Hikuai suffered significant damage with the road collapsing after the North Island’s major storm event in late January 2023. The road was closed while a new bridge is built, and reopened on 20 December 2023.
On 15 January 2023 cracks were first seen on the surface of SH25A.
On Friday 27 January the road was fully closed to ensure the safety of people using the road and our team on the ground. During the storm event later that day, the cracks widened and worsened and a significant section of SH25A collapsed. The site continued to be active for several days after, with further material slipping into the gully below.
Work began immediately to determine the best option for reconnecting SH25A. A bridge was confirmed as the best option to fix SH25A, based on the ability to build back better in the shortest timeframe.
An artist rendition of the bridge
A bridge was selected as it would reconnect the Coromandel Peninsula communities most quickly, it’s the safest and most resilient option, and work could continue throughout winter.
Waka Kotahi selected, a joint venture between McConnell Dowell and Fulton Hogan, supported by Beca and Tonkin and Taylor to design and build the bridge.
While the type of bridge proposed would usually be expected to take 12 to 14 months to construct, Waka Kotahi worked with the joint venture to accelerate delivery with the initial aim of having the route open by the end of March 2024.
By mid-November 2023, the bridge deck was in place and it was announced the road would reopen before Christmas 2023, three months earlier than initially proposed.
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Multiple slips from ex-Tropical Cyclone Hale closes SH25A for much of 11 January.
Cracks are first seen on the surface of SH25A on 15 January, and the highway was closed for safety and to allow full investigation. Monitoring devices were put in place to detect further deterioration, and the highway re-opened on 18 January to one lane during 7am–7pm with a temporary speed limit of 30km/h, while monitoring and investigations continued.
Heavy rain causes further instability at the summit on 27 January and new cracks continue to appear. The road was again fully closed to ensure public safety. During the Auckland Anniversary weekend storm event, a large section of the highway at the summit collapsed and slipped away.
The remainder of the road collapsed into the gully on 30 January, after yet more heavy rain.
Work begins to plan the solution to restore the road, with specialist contractors and geotechnical engineers engaged.
Government Ministers visit the site to see the extent of the damage.
After Cyclone Gabrielle, it’s clear the underslip has deteriorated further.
In late February, three options for the rebuild solution are announced: 1. To retreat north and build a bypass road around the top of the site. 2. To replace the lost section of road with a bridge. 3. To rebuild the highway from the bottom up, using retaining walls.
The crater now measures approximately 130m across and 30m deep.
Temporary tracks are formed to enable access for the geotechnical drilling rigs. Geotechnic investigations are completed to assess the soil and rock profile underneath the crater and on the site of the potential bypass road.
The options assessment report is completed, and a best option determined
A bridge confirmed as safest and most resilient option, with shortest timeframe for reconnecting Coromandel communities.
Waka Kotahi engages with the construction industry and the procurement process begins.
A preferred tenderer is identified. Work starts on enabling works, site establishment, access tracks and bridge piling starts.
Bridge piles and piers are completed. Abutments, bridge deck works and bridge approaches are underway.
The 138 bridge deck panels are installed by mid-November, with the 44 side barriers installed later in the month.
Bridge approaches, pavement, final asphalting, road marking and barriers will be completed during December, and the bridge reopened to traffic on 20 December.
Remaining site stabilisation and drainage completed, debris removal and site disestablished.
