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From quarry to human dung hole

A former quarry on a sacred Maori island in New Zealand is being rehabilitated in a world first biosolids project – using treated human faeces.

In the 1950s and 1960s, around 915 million cubic metres of scoria and basalt rock from the volcanic cones on Auckland’s Puketutu Island were used to construct Auckland Airport’s runway and the Mangere Wastewater Treatment Plant.

As part of the current project, four volcanic cones that were destroyed during the quarrying operation will be rebuilt. Watercare, a water and wastewater company affiliated with the Auckland Council, estimates that 4.4 million tonnes of biosolids, comprising of treated human waste, will be used to fill the former pit.

“I don’t know of anyone who does what we do,” Rob Tinholt, Watercare’s resource recovery manager told “To have a monofill [sewerage/sludge-only landfills] of this scale of biosolids … is unique.

“What’s commonly done throughout the world is applying biosolids to land as a fertiliser, and another way is in landfills, either as a waste put in or as daily cover material for the rubbish.”

The site has been divided into 18 cells; the treated biosolids form the foundations of what will eventually be four hills to replicate those previously quarried.

Each cell is 25m wide and mesh separates the biosolids and soil layers. Around 300 tonnes of biosolids are transported to the island every day in side-tipping trucks that dump the material directly into the cells.

The first biosolids were tipped into the former quarry in 2014. According to Watercare, by 2024, construction will be complete and “operational filling” will be carried out.

The final “capping” phase will involve contouring, topsoiling and planting. It is hoped that by 2049 Puketutu Island will be transformed into a regional park for the people of Auckland to enjoy.

Watercare personnel insist that no odours are expected on completion of the project and tourists will not be able to smell the treated human waste beneath their feet.

Territorial right

The island is sacred to mana whenua (Maori territorial rights; power associated with possession and occupation of tribal land). Some iwi (tribe) groups initially opposed the project.

The island was the first permanent home of the Tainui waka in Aotearoa after it had been carried overland from the Waitemata to the Manukau Harbour.

Te Warena Taua, the chairman and spokesperson of the Te Motu a Hiaroa Charitable Trust, which holds the freehold title of the land, said the island is of immense cultural, spiritual, historical and ancestral significance to mana whenua.

“It is, in essence, the spiritual centre of Tainui within Tamaki Makaurau and is a revered and central locale for the spiritual wellbeing of Te Kawerau a Maki and Te Waiohua,” Te Warena Taua told

Under an agreement reached out of court, the island’s governance trust, comprised of representatives from Auckland Council, Watercare and iwi entities Waikato Tainui, Te Kawerau a Maki and Makaurau Marae, receives $2 per tonne of biosolids from Watercare. According to Taua, the funding will be put towards key cultural initiatives on Puketutu.


More reading:
Expansion plans greenlit for mountainside quarry 
NZ capital to address impending aggregate shortage 
New solution for cost-effective water treatment 
Biowaste used to reclaim quarries
Generating power from ‘holey’ ground
From making to filling holes


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