Auditors raise estimates of waste at Tiwai Point, months after Government questioned provision 30 Apr, 2021 05:25 AM 4 minutes to read The Tiwai Point site has been operating as an aluminium smelter for 50 years. Photo / Supplied The Tiwai Point site has been operating as an aluminium smelter for 50 years. Photo / Supplied Rio Tinto has revealed there is more hazardous waste at the Tiwai Point aluminium smelter than previously thought, forcing it to raise the provision for cleaning up the contaminated site. The added material was picked up in a routine audit, about five months after Finance Minister Grant Robertson wrote to directors of the smelter questioning the basis upon which they were preparing to cover the costs of closure and clean up.