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, with the bridge to open to traffic by 20 December.
Remaining site stabilisation and drainage completed, debris removal and site disestablished.