The Puketutu Rehabilitation Project in Auckland’s Manukau Harbour began in 2012 on behalf of Watercare. To meet Auckand’s future needs, a safe location was required to dispose of waste solids from the wastewater treatment plant in Māngere. The plant produces about 330 tonnes of treated biosolids a day. Instead of sending the biosolids to the landfill, they are transported to neighbouring Puketutu Island.

The first biosolids were delivered to the former volcano site in 2015 and new storage cells were developed in parallel. A 450,000 m3 bund has been built around the perimeter and nearly 60,000 m2 of liner laid, about the equivalent of 12 rugby fields. A significant amount of clay was supplied to the project by Clevedon quarry. Aggregates Sales and Logistics Manager Aaron Fraser says, “Throughout 2022 and 2023 we supplied 225,000 tonnes of quarry overburden for use within the biosolid liner system”. The sealed liner and pump system captures any biosolid leachate and returns it to the Māngere plant, protecting the island’s aquifer. The final liner section was installed in early March 2024 and the project is now in its final three months of construction.

Puketutu Project Manager Russell Green says, “Sometimes it’s easy to think this is normal, to forget that this is an extraordinary project, unique in its creativity and practicality and one which we’re extremely proud to have been involved with.”