Te Wānanga

To help restore the Mauri (life force) of Te Waitematā and Tīkapa Moana (the Hauraki Gulf), a co-design partnership between Mana Whenua, Isthmus, Auckland Council, Auckland Transport, Tonkin + Taylor, the aquaculture industry, and the Downtown Joint Venture delivered a first of its kind kūtai restoration project. While subtidal kūtai reef restoration is occurring in the wider Tīkapa Moana, a system of this kind in a fully urban environment has never been attempted in Aotearoa New Zealand.

Green-lipped mussel (kūtai) (Perna canaliculus) restoration is incorporated into the design to re-establish ‘living’ systems in Tāmaki Makaurau’s urban marine environment. Kūtai were once abundant in the Hauraki Gulf before overfishing and pollution caused stocks to collapse in the mid-1900s. Successful translocations have been undertaken as part of the ‘Revive our Gulf’ project but never attempted in the city centre.

Trials of co-designed pile wraps and a novel floating buoy system seeded with 90 m of kūtai were deployed in June 2020 to inform a larger deployment in May 2021. If successful, the kūtai would provide biodiversity and water quality improvements. The project’s location afforded other exceptional opportunities. If the public could see the kūtai and be educated about their benefits, they could be used in an advocacy role, supporting the health of Tikapa Moana.

Trials resulted in the development of a bespoke non-tidal float system to carry the kūtai at the water’s surface. Floats developed by Tonkin + Taylor and Quality Equipment Limited were adapted to the local environment. Using wave modelling to help inform the approach, a custom-built line and anchor system was devised to hold the floats where the public could see them. Without the floats, the mussels would be hidden from view for much of the tidal cycle.

Providing kūtai floats and lines beneath Te Wānanga has increased biodiversity through the establishment of a native taonga species which can outcompete invasives. Monitoring kūtai floats has shown that seeded kūtai lines have a higher diversity of species and groups than blank lines, with abundant bryozoans, sponges, anemones and polychaete worms present. Mobile species observed include glass shrimp, triplefins and crabs. A mixture of native fish species has been observed schooling around and within the floats, highlighting the nursery function that kūtai provides.

The kūtai and the diverse species assemblage they provide contribute to ecosystem services such as habitat provision, water filtration and carbon sequestration. A single kūtai can filter around 100 litres of seawater per day, removing pollutants and improving water clarity. With 600 metres of kūtai lines and about 200 kūtai per metre, this equates to 12 million litres of seawater being filtered per day, helping to restore the Mauri of Te Waitematā.

Following the trial, in May 2021, a bespoke freshwater treatment system was created to remove invasive species from the kūtai. Then, 600m of kūtai lines were deployed in a woven pattern onto 38 floats along the front edge of Te Wānanga – prominently displayed in the heart of downtown Tāmaki Makaurau.

Structural innovations; evoking the natural environment

Te Wānanga’s irregular concrete deck shape, evocative of a coastal sandstone shelf and its suspended steel planters, demanded inspired thinking – a team willing to go beyond norms and an unwavering dedication to safety, and supporting a flourishing terrestrial and marine environment.

The irregular, complex geometry was challenging to analyse, design and construct. Te Wānanga’s innovative structural design employs both displacement-based design and non-linear soil-structure interaction modelling – a technique outside the scope of the New Zealand codes. The geometry and the large length of the jointless deck necessitated a very high reinforcing density – approximately triple that needed in a conventional deck – with joints at 500 kg/m³ of concrete. To assist the deck slab’s construction, a three-dimensional design model was created with the reinforcing bars explicitly modelled. This helped with clash detection and informed the constructor’s sequencing when fixing the reinforcing.

A true co-design process with shared learning

Establishing a co-design process with Mana Whenua, the designers and client developed the overarching project concepts of manaakitanga (hosting, generosity) and mīharo (extraordinary) and Auckland to Tāmaki Makaurau (authentic and beautiful Tāmaki) at the beginning of concept design. Crucially, this collaboration was maintained throughout the design process – from concept through to detailed design.

To deliver a space worthy of these drivers and the vision for a world-class waterfront recognising its cultural and historic heritage, Auckland Council entered into a design partnership with Tonkin + Taylor, Isthmus, Mana Whenua and Auckland Transport to deliver this project as part of the Downtown Programme. The shared learnings provided by the co-design process saw every project team member emerge enriched from the experience.

The co-design and development of the first of its kind kūtai float and anchor system reflect the brilliance of a true design partnership. Knowledge was drawn from mātauranga Māori, the aquaculture industry, landscape designers, scientists and engineers to develop a truly remarkable approach to restoring Tāmaki Makaurau’s urban marine environment. Visitors are excited and surprised to see the kūtai thriving, highlighting Te Wānanga as an excellent vehicle for further public engagement and partnerships.