Monday 30 January: Cracking on the section of SH23 known as the Raglan Deviation (‘the Raglan Divvy’) to the west of Glentui Lane was identified following the major storm event that hit much of the North Island. One lane was affected, and the road was reduced to one lane under stop/go traffic management. Metal was placed on the shoulder of the road to increase the road width, moving traffic further away from the edge of the cracking, and an asphalt bund was created to try and stop water running into the cracks.
Tuesday 31 January: The site was monitored throughout the day, and the cracking widened and worsened, along with slumping of the road by approx. 200mm.
Wednesday 1 February: The decision was made to close the road overnight from 7pm to 7am until an urgent assessment was made. Early geotechnic work indicated the site was saturated, and the concrete kerb and channel had fully cracked through, letting water into the underslip.
Thursday 2 February: The road was closed to all traffic, with geotechnical engineers carrying out drilling and core penetration tests to investigate the severity of the situation and ongoing risk.
Early-February: With no chance of utilising the existing roadway, work began to build a diversion around the underslip.
Saturday 4 March: Waka Kotahi opened a two-lane temporary diversion road on private property that skirts the underslip. The diversion road allowed the time to investigate and plan the long-term restoration.
6-13 March: Underslip stabilised with soil nails, while investigation and planning continued.
Tuesday 14 March: Solution decided: a geosynthetic-reinforced retaining wall with Continuous Flight Auger concrete piles.
Thursday 16 March: Rig established on site.
Friday 17 March: Concrete drilling began.
Friday 24 March: Construction of retaining wall began.
Early May: Retaining wall completed.
Mid May: Traffic returned to the original highway.
29 May: Paving and asphalting completed.
Early June: Lane markings and guardrail installation completed.