Dome Valley — SH1 Landslide

An unprecedented weather event in 2023 caused a landslide blocking part of SH1 near Dome Valley, north of Auckland. The failed slope face was inaccessible from the road below and from the hillside above without preparation. Our design team specified a helicopter landing area to be cut into the upper slope — the only viable access point for personnel, plant, and materials.

Three weeks of site preparation preceded the main stabilisation works, including creation of the landing area, temporary rainforest tracks, and a bridge across Hoteo Stream for reliable access during rainfall. The design solution centred on a dimensioned soil nail system using Geobrugg G65/s TECCO mesh — a lightweight, high-tensile mesh system that could be transported and installed entirely via rope access and aerial delivery, without requiring heavy plant on the slope face itself. The Dome Valley project was delivered as a design-build contract, with GSI's in-house engineers developing the solution and the same team constructing it from helicopter-accessed positions above the slope.

The completed works delivered 118 installed rock anchors across the face, with 790 m² of Geobrugg TECCO G65/s mesh covering the stabilised slope. The system provides permanent protection against further rock movement and slope failure, with the mesh system designed to intercept and retain any future loose material above the highway corridor.

Works were completed within programme, SH1 traffic impacts were minimised throughout, and the site was left to full DoC and iwi satisfaction. The Dome Valley project is a demonstration of what is achievable through thorough pre-planning and rope access methodology on sites where standard access is simply not possible. GSI NZ provides landslide stabilisation and slope repair services across New Zealand, with specialist capability for remote and inaccessible sites.