Project Overview
A wet winter in Wellington in 2022 destabilised a road reserve slope in a residential suburb, resulting in a landslide that undercut a private property above and threatened the road below. Wellington City Council awarded the slope stabilisation contract to Geovert.
The slope face was up to 20 metres wide and 16 metres high. Lennel Road runs directly below it and had to remain open to traffic throughout construction. A residential property sat at the crest, and a public footbridge crossed directly above the worksite, making the project highly visible to the community.
What initially looked like a contained urban stabilisation job became more complex once work began.
What the site demanded
The original scope - an anchored mesh and shotcrete retaining wall across the landslide face - was straightforward enough in principle however executing it on this site was not.
A services scan at the crest of the slope revealed a dense network of underground utilities that ruled out rope access in the area where the shotcrete ribbon needed to be applied. This was not identified at tender and required an immediate design response. Working with geotechnical engineers ENGEO, Geovert developed a bespoke scaffold system that could be installed above a live road, within a narrow corridor, and still allow accurate shotcrete application as work moved down the face.
The scaffold solution introduced its own complications. The slope steepened as it rose, which meant the geometry of each scaffold drop changed as work progressed. Close coordination between the scaffold subcontractor and the Geovert team was required to keep each drop feasible as the face being treated shifted.
A further constraint emerged during debris clearance with asbestos contamination in the material being removed. This had not been anticipated at tender and required Geovert to bring all personnel involved in clearing and scaling works up to the required certification standard with training under the Health and Safety at Work (Asbestos) Regulations 2016 - before that phase of work could continue. Environmental controls were extended accordingly, with water suppression and effective ventilation added to manage dust exposure for both crew and the surrounding neighbourhood.
The drilling approach
Three drilling methods were used in combination across the face, each addressing a different part of the access problem.
Wagon drills with anchors worked the upper section of the slope. A scaffold-mounted drill mast handled the areas where the services above had ruled out rope access. An excavator-mounted drill mast with a custom three-metre boom extension worked from the base, significantly extending reach in a workspace that offered little room for conventional positioning.
The three methods had to be sequenced carefully to avoid interference between phases, particularly as the scaffold changed configuration with each drop down the face.
The mesh installation added another layer of coordination. ENGEO's design called for an intricate cable layout across the retained face to provide adequate tensioning, which required careful construction sequencing and forward planning to manage.
Program and outcome
Wellington City Council's original program called for ten weeks. The services discovery at the crest, which required the scaffold solution, and the asbestos contamination, which added a separate management programme, extended the timeline by agreement with the client. Geovert worked additional days and weekends to absorb weather delays within that revised schedule.
The completed retaining wall stabilised the slope and allowed the private property above to be reoccupied. Wellington City Council noted their satisfaction with the outcome and with the team's communication with the local community throughout.
"Looking forward to working with Geovert again in similar jobs in the future." Wellington City Council
A year on, the site shows minimal impact on the surrounding environment.
This project was recognised as a finalist in the Civil Contractors New Zealand Awards 2025.
