Landslip Remediation & Retaining Wall

The extreme rainfall event over Auckland Anniversary Weekend in 2023 triggered widespread slope failures across the region. On steep residential sites, land loss occurred dangerously close to dwellings, leaving homeowners facing uncertainty, insurance challenges, and significant geotechnical risk.  For this property, a deep-seated slope failure developed immediately adjacent to the dwelling, compromising land stability and threatening the safety of the structure. 

Cook Costello was first engaged to assess the land damage and assist the owners through the insurance process. Our independent engineering assessment helped establish the extent and cause of the failure, enabling the owners to access the land damage cover they were entitled to under the EQC Act.  Following the successful claim, we continued our involvement through the full remediation phase. 

Our Role Included: 

• Detailed geotechnical investigation to assess the landslide mechanism, subsurface conditions and ongoing stability risks 

• Development of a remedial stabilisation strategy suitable for a deep-seated slope failure 

• Integrated geotechnical and structural design of a retaining wall system to stabilise the slope adjacent to the dwelling 

• Preparation of consent documentation to support Auckland Council building consent 

• Construction monitoring and PS4 producer statements to certify the works were built in accordance with the design intent 

The solution combined robust geotechnical analysis with structural retaining wall design, ensuring both immediate stability and long-term resilience. 

The slope has now been stabilised and the dwelling safely reoccupied. The site is significantly more resilient to future heavy rainfall events than it was prior to the 2023 storm. 

Importantly, the owners were supported from initial damage assessment through to final certification, providing continuity, clarity and confidence during what was a highly stressful time.