Local councils in Southland, the government and the Tiwai aluminium smelter company have been negotiating since the end of last year on how to split the costs.
The liquidators of the waste processing company Taha walked away late last year from the job of cleaning up at least 22,000 tonnes of so-called Ouvea premix which was stockpiled in Mataura and around Invercargill.
They said they could not get the funding.
Gore District Council, which brokered the deal, said the smelter company and government would combine to cover three quarters of the $4m cost.
The remaining 25 percent would be split between the Gore district, Southland district, Invercargill city and Southland regional councils.
Officials have not yet confirmed where the waste will be sent.
