In our 'What Good Looks Like Series' we're examining what good looks like across the different types of work we do, from emergency response slope stabilisation and mining ground support to geohazard mitigation and asset integrity maintenance. These aren't showcases of perfect projects with ideal conditions. They look at real work where solutions had to adapt as conditions changed, where collaboration shaped outcomes, and where technical expertise met practical constraints.
Project Overview
State Highway 1 through the Brynderwyn Hills carries roughly 15,000 vehicles daily and is the main artery connecting Northland to the rest of New Zealand for both people and freight. The route traverses steep terrain with a long history of instability, but the weather events of early 2023 exceeded anything in recent memory. Severe underslips and overslips closed the highway, cutting off the region and requiring immediate emergency response.
The key question for the New Zealand Transport Agency (NZTA) wasn't just how to reopen the road, but how to make it resilient enough to withstand future weather events without repeated closures. The decision-making was complicated by the planned Northern Corridor, a new route that would eventually replace this section of SH1. This meant finding a balance between adequate resilience and appropriate investment for infrastructure with a 10-15 year design life.
The answer required early engagement with a 12-month Early Contract Involvement (ECI) phase which brought Geovert together with WSP as design engineers, Fulton Hogan as head contractor and NZTA to workshop options ranging from minimal intervention through to gold standard solutions. Geovert provided the construction perspective throughout this process, assessing how different stabilisation methods would perform given the site conditions.
Rapid Response Planning
The emergency nature of the initial response meant that design and construction had to proceed almost simultaneously. WSP was developing solutions while Geovert was preparing to build them, often with minimal lead time. This placed unusual demands on logistics and planning. Equipment configurations had to be prepared and ready to mobilise at short notice - crawler rigs, excavator rigs, wagon drills, high reach drills - so that whatever the design required could be delivered quickly.
The nearby concrete yard became the staging area where materials could be prepared, tested, and approved to the engineer's specifications. In-situ anchor testing and concrete testing were conducted throughout the project, with rigorous quality control processes established through close consultation between Geovert and WSP.
Continued severe weather brought further slips and destruction, extending both the timeline and the technical requirements. What began as emergency stabilisation evolved into a comprehensive resilience project requiring multiple technologies and approaches across varied terrain.
Finding Solutions in Difficult Corners
One particular challenge arose on a tight hairpin corner where downslope concrete had to be installed in hard-to-reach locations while keeping SH1 operational. The design called for shotcrete, but the methodology - completing the work via rope access to allow the road to remain open - presented practical difficulties. Geovert recommended switching to gunnite, applied through a pneumatic drycrete pump.
Gunnite was an infrequently used technique for Geovert in this context. The pump was a new larger capacity model and was ordered from an overseas supplier and delivered within two weeks, but getting the aggregate materials ratio correct proved difficult initially. A couple of small sections cracked and failed. Geovert consulted with suppliers to refine the application process and made good the failed sections. The technology worked, and it proved well-suited to the constraints - the tight corner and limited space on the road meant a lower footprint technique was necessary. Gunnite addressed both the access constraints and reduced the physical demands on our rope access technicians.
Managing Instability
Steep terrain and changing ground conditions created ongoing safety challenges. Geovert worked closely with Fulton Hogan and WSP to establish a collaborative project culture where safety concerns were raised immediately and acted upon without hesitation. Daily pre-start meetings ensured clear communication across crews, and lessons learned were integrated quickly into procedures.
The value of this culture became evident when one of Geovert's rope access workers felt something wasn't right while working on a slope and reported it immediately. The work zone was cleared without delay and later that day, the slope slipped. It reinforced the understanding that these were unstable slopes in active movement, and the work itself could trigger further failures.
Geovert's slope stabilisation experience became particularly valuable when assessing whether to use battered slopes or mechanically stabilised solutions. Our experience with different soil groups and drilling methodologies in varied conditions informed constructability discussions. Maintaining multiple plant and equipment options on standby allowed the team to adapt as conditions changed across the eight sites.
Environmental Constraints in a Scenic Corridor
The Brynderwyn Hills section of SH1 passes through ecologically significant native bush, a scenic gateway to Northland. Working in this environment with cementitious materials required careful controls. The downslope shotcrete application directly adjacent to the road created dust that affected both the surrounding bush and road users. Geovert set up a series of misting locations to mitigate airborne particles.
Throughout the project, the environmental management plan ensured that the work didn't compromise the landscape it was meant to protect.
Geovert also took proactive steps when field observations revealed risks beyond the work areas. When evidence of rockfall appeared on a slope adjacent to where crews were working, the team quickly notified the engineer and installed temporary mesh netting to protect the road below. This rapid response maintained open access on SH1 and prevented what could have become another closure.
What Made It Work
The Brynderwyn Hills Resilience Project required trust and communication between NZTA, WSP, Fulton Hogan and Geovert that allowed for rapid decision-making under the expanding scope and constantly changing conditions.
Early involvement by Geovert's team meant slope stabilisation solutions could be assessed for constructability as they were being developed, ruling out approaches that looked viable on paper but wouldn't work in practice. When weather brought further slips and ground conditions changed, the collaborative approach allowed plans to adjust based on field observations rather than rigid adherence to initial designs.
The scope ultimately included 5,000 lineal metres of grouted ground anchors installed across varied terrain, nearly 1,000 square metres of mesh installation both upslope and downslope, and specialist rope access work in heavily bushed areas. Multiple drilling methodologies - from wagon drills to excavator-mounted and crawler rigs - were deployed as conditions demanded across the eight sites.
What Good Looks Like
In emergency slope stabilisation on transport corridors, success is not only defined by how quickly a road is reopened, but by whether it can remain safely open as conditions continue to evolve.
SH1 through the Brynderwyn Hills now has geotechnical stabilisation designed to withstand future weather events. The outcome reflects the incredible effort of everyone involved - a genuine collaborative achievement.