Sunkist Bay Slip Stabilisation Works

Earth Stability was awarded this measure and value project through direct negotiation, with WSP Opus appointed as engineer.

The project included a 32-metre in-ground timber pile wall formed from 32 eight-metre poles embedded seven metres into 600mm-diameter holes. A continuous timber waler was tied back with 33 ground anchors, each 14.5 metres long.

Slope reinforcement comprised 300m² of turf reinforcement matting overlaid with double-twist rockfall mesh and 90 ten-metre soil nails. The drainage system included 750 metres of bored horizontal drains, manholes, subsoils and outlet structures.

A further 1,500m² of lower slope was treated with coconut matting and native planting. Approximately 6,000m³ of slip debris was excavated, moved and recontoured from the beach and seawall to the toe of the slope, with much of the material modified using lime and cement stabilisation.

The site is within a Significant Ecological Area and beside a popular public walking track. The work extended across Department of Conservation, Auckland Council and two privately owned properties, requiring a coordinated and sensitive approach.

Access was along the public walkway above the existing seawall, with most work completed during winter. A specific methodology protected the sensitive environment while maintaining public safety and minimising disruption. The project was a finalist in the 2019 CCNZ Construction Excellence Awards and was completed on time, to specification and on budget.