ICB Retaining & Construction

CATEGORY 1B: Projects with a value of less than $5 million (Company turnover greater than $10 million)

PROJECT: Kopupaka Reserve – Timber Crib Pond Structures. CONTRACTOR: ICB Retaining & Construction

Aesthetic appeal

The Kopupaka Reserve, near the Westgate Town Centre in northwest Auckland, forms an integral part of the commercial and shopping hub and acts as a green space for public enjoyment. The reserve features walkways and water-retaining areas over the 50-hectare site.

As a part of the development ICB Retaining & Construction (ICB) was contracted to construct the feature walls for the retention of the stormwater ponds, the inlet and outlet structures, public viewing platforms and various other backfilled retaining walls. The design of the walls, which was inspired by the flax woven baskets of early Maori, was completed by the Isthmus Group and required the construction of curved, lattice-like, timber crib retaining walls. This was both challenging and innovative by the very nature of the curvature of the walls – believed to be a first of its type in New Zealand.

Due to the complexity of the design, ICB first built test walls to gauge the strength of the timber curvature, cambered footings and the effect this was going to have on the higher sections of the walls.

Actual construction comprised the creation of curved and cambered concrete footings, installation of 24 timber piles between the box culverts and within the timber crib, compacting GAP65 at the base, installing 24,000 timber crib stretches and headers, placing gabion basalt rock within the crib cells and steel strapping within the crib to prevent twisting and warping. In addition there was the challenge of accurately fitting 350mm SED poles in between the timber crib cells.

To comply with the ecological requirements, the outlet structures feature fish ladders to ensure that the vitality of the catchment is maintained.

The highest standard was achieved in the construction, with materials and performance monitored throughout the project. This included geotechnical investigations, maintaining drilling logs, testing and certification of materials used in the construction – all of which were documented.

The completed project has stunning aesthetic appeal and has added another dimension to the reserve. The quality and delivery of the project was recognised by the client, with the design winning the Landscape of the Year Award at the 2016 World Architecture Festival in Berlin. l