The removal of hazardous ouvea premix from the former Mataura paper mill is scheduled to begin within the next three months under a contract secured by the Gore District Council.

The contract with Australian-based company Inalco Processing Ltd will remove 22,000 tonnes of the substance from sites in Mataura and Invercargill over the next six years.

Gore District chief executive Stephen Parry said the contract ensured the 10,000 tonnes of premix stored at the Mataura paper mill would be moved first.

“This acknowledges the significant risks posed to both the environment and people by having the premix stored next to the Mataura River," Mr Parry said.

Ouvea premix is a by product from the processing of aluminium dross from the New Zealand Aluminium Smelters' Tiwai Point smelter, south of Invercargill. It's a class 6 hazardous substance and releases poisonous ammonia gas when hydrated.

Taha Asia Pacific started storing ouvea premix at the former Carter Holt Harvey paper mill, in Mataura, without resource consent in 2014. It applied for and was granted a consent retrospectively in 2015. The company went into liquidation in 2016.

There were logistical details to work through and Inalco was required to provide a risk management plan before removal could begin.

“It’s important we take all precautions to ensure the transfer of the premix doesn’t put the community or environment at risk," Mr Parry said.

“This is a hazardous substance and needs to be treated with respect.”

The ouvea premix will be transported to Inalco’s processing facility, situated within New Zealand Aluminium Smelters’ site south of Invercargill, where it will be processed and converted into a raw material for future use.

Mr Parry acknowledged the flexible attitude shown by NZAS in allowing Inalco to process the premix at the Tiwai Point site, saying “it was an important factor in getting the contract finalised."

All parties involved have pledged a total of $4 million.

Under the terms of the contract, New Zealand Aluminium Smelters will contribute $1.75 million and the Ministry for the Environment will pay $1.25 million from its Waste Minimisation Fund.

The landlords will contribute $350,000, while the remaining $650,000 will be paid by all four Southland councils (Environment Southland will contribute $250,000, with the remaining $400,000 apportioned on a per capita basis among the Invercargill City Council, Southland District Council and Gore District Council).

The Invercargill City Council contributes as a landlord and a local authority.

Mr Parry, who has been at the forefront of securing the deal, said the contract was the culmination of 18 months of “very taxing and convoluted” negotiations.

“In my many years as a chief executive I have never been involved in something as all-consuming as this.”

Mr Parry said he understood the extremely cautious approach taken by the other parties and acknowledged the compromises made to reach an agreement.