Hetherington Road Landslip

McCaffrey & Cable Consultants (MaCC) were engaged by Waikato District Council to provide geotechnical and civil design services to remediate a landslip along Hetherington Road, west of Ruawaro.

The failure occurred on a steep ridgeline section of road, resulting in cracking and settlement of up to 500mm across the carriageway. The landslip extended approximately 24m in width, impacting a key rural route carrying around 100–500 vehicles per day. Investigations identified weak fill and colluvium overlying weathered siltstone, with shallow groundwater and a natural spring contributing to ongoing instability.

MaCC undertook detailed site investigations, mapping, and geotechnical analysis to develop a practical and robust solution. The design involved excavating the unstable material down to underlying rock and reconstructing the embankment using engineered rockfill. A shear key was incorporated at the toe to improve global stability, while free-draining materials were used to reduce groundwater pressures. Slope stability modelling confirmed the design met performance requirements under traffic, flood, and seismic loading conditions, with a design life of 50 years adopted for the works.

MaCC were also engaged to assist with construction cost estimates and construction stage advice relating to earthworks, culvert reinstatement, and reconstruction of the pavement to restore the road to its original level and alignment.

The result is a practical and durable solution that addresses the underlying failure mechanism and improves the long-term resilience of this important rural transport route.