Prole Road, Omokoroa – Retaining Wall, with Platipus anchors

Stretching from Õmokoroa Road to the Waipapa River, Prole Road is a key component of Õmokoroa’s future urban development. The $23.5 million upgrade will support more than 2,500 new homes, a future town centre, schools, and upgraded transport infrastructure.

A major challenge within the project involved widening the road along a steep embankment adjacent to a gully and stream. With residential access needing to remain operational throughout construction, extensive excavation was not practical. Higgins required a solution that could be installed within a constrained workspace, minimise disruption to residents and traffic, and provide immediate structural performance.

Platipus Civil Anchors delivered the ideal, robust retaining solution, minimizing retaining wall pile depths and keeping the project moving and local access maintained.

DESIGN

To avoid extensive excavation and reduce construction impacts, a timber pole retaining wall reinforced with Platipus B10 Civil Anchors was selected.

Installed up to 10 metres behind the retaining structure, the anchors provided the required soil reinforcement while maintaining the stability of the surrounding area. Following site testing, CMW determined the required design loads, ensuring the anchor system achieved the necessary performance criteria.

Compared with traditional grouted anchoring systems, the cantilever retaining walls with Platipus Anchor tiebacks offered several key advantages:

• Minimal excavation and soil disturbance
• Suitable for constrained sites with limited working room
• Loadings can be accurately tested to verify performance
• Reinforced areas become operational immediately after testing
• Reduced programme risk and construction time

To further maximise available space and improve constructability, ArmourFlow Panel Drain was specified in place of conventional drainage aggregate and geotextile layers.

INSTALLATION

Working from the top of the slope, NZ Structures installed the Platipus B10 Anchors using a hydraulic rock breaker mounted to a crane. The anchors were driven to the specified 10 metre depth using a series of steel drive rods and extenders.

Once installed, each anchor was tensioned and proof-tested to confirm the required holding capacity before being connected to the timber waler system. The ability to verify anchor performance onsite provided confidence that the retaining structure could be loaded immediately without waiting for additional curing or construction stages.

The flexibility of the Platipus system also proved valuable when services needed to be installed alongside the road. Extender rods were temporarily modified to accommodate the new pipework before being reconnected, without compromising the original anchor loads.

By using Platipus Civil Anchors, the project team was able to:

• Maintained resident access throughout construction
• Restricted traffic management to a single lane rather than a full road closure
• Minimised excavation and environmental disturbance Reduced retaining wall post lengths
• Worked efficiently within a tight construction corridor
• Reduced construction costs
• Reduced construction delivery timeframe
• Delivered a tested, immediately functional retaining solution

The Platipus Anchors provided the following benefits to the project:

• Fast Installation –  Rapid installation and immediate load testing help keep projects on schedule.
• Minimal Site Disruption –  Small installation footprints reduce excavation requirements and minimise disturbance to surrounding infrastructure and environments.
• Proven Performance –  Every anchor can be tested to a specified holding capacity, providing confidence in long-term performance.
• Flexible Design Solution –  Suitable for retaining walls, slope stabilisation and earth reinforcement applications where traditional systems may be impractical.
• Ideal for Constrained Sites –  Allows critical infrastructure projects to proceed safely where working space is limited and access must be maintained.