Bluff's Tiwai Point Aluminium Smelter is storing 36,000 tonnes more hazardous waste on site than it previously reported.

New Zealand Aluminium Smelter, owned by global mining giant Rio Tinto, today updated the reported volume of spent cell liner waste [SCL] stored at Tiwai Point to 217,000 tonnes, up from the 181,000 tonnes it reported in March.

SCL contains hazardous chemical compounds including fluoride and cyanide. It produces explosive gases when mixed with water.

NZAS has come under fire recently after it was revealed it is storing more than 100,000 tonnes of the material less than 100 metres from an eroding beach.

Independent auditors confirmed the adjusted totals following a survey of the Tiwai Point site as part of NZAS’ annual financial reporting process.

In a press release today, NZAS reiterated it is committed to removing all SCL. Financial provisions have been increased accordingly to ensure the responsible management of all material stored on site.

NZAS chief executive and site general manager Stew Hamilton commented: "We want to make sure the community is aware of the adjusted quantity.

"I want to be very clear that regardless of the amount, we remain committed to removing all of the material from the site to be recycled or disposed of safely and securely in accordance with modern standards.

"This adjustment will not have a material impact on the timeline for removal.

"The material is secure and safely stored, as confirmed by Worksafe inspectors during their visit in February."

This year marks 50 years of continuous operation at Tiwai Point and NZAS continues to conduct regular and extensive environmental monitoring of the site, recently releasing assessments of the groundwater surrounding the SCL storage facilities, the release adds.

"I am confident that our environmental monitoring systems give us ample warning of any issues and enable us to remediate or alter processes to halt any breaches becoming harmful.

"There has never been an instance during our 50 years of operation which could harm the public or local communities,” Hamilton says.

Spent Cell Lining, or SCL, is the material left in the cells which are taken out of circulation to be re-built.