Toxic waste concerns for Tiwai
Ex-staff claim that material is buried at Southland’s smelter
Investigators are looking into claims highly toxic waste has been buried in unmapped sites at the Tiwai Pt aluminium smelter. This includes spent cell liner (SCL) waste that contains cyanide and toxic fluoride, and is banned from being buried untreated in both the United States and Australia.
The warning last October from the compliance section of Environment Southland is in documents released to RNZ under the Official Information Act.
“Former staff of the smelter report burying of spent cell linings or contaminated material in various parts of the Tiwai site,” said the report into “key matters” for cleaning up the huge site next to conservation land once the smelter shuts in 2024.
Waste burial reportedly went on “particularly prior” to the Resource Management Act’s enactment in 1991, by which stage tens of thousands of tonnes of hazardous waste had already been produced.
The report followed this with a warning: “It is likely that a number of unmapped or unconsented contaminated sites exist as a result of these uncontrolled activities.”
The Government has said it is “blind” on contamination at Tiwai, and abruptly called off talks with Rio Tinto last month, until the company gives it more information.
The Rio Tinto-controlled New Zealand Aluminium Smelters (NZAS) company is also reportedly not sure what it will find underground, though its pollutant discharges have been consented, at least since the 1990s.
NZAS and the Government have parallel investigations going on to uncover what is there.
The smelter company denied any material had been buried. “We are unaware of any material being buried at NZAS, in unmapped or unconsented sites,” chief executive and general manager Stew Hamilton said in a statement.
“The detailed closure study, currently under way, will examine the site footprint including management of all waste products. This complements existing monitoring to inform closure and remediation options.”
RNZ asked Environment Southland what it is doing to ascertain if the reports of buried, unmapped waste are true.
The regional council told RNZ in a statement it had discussed historic dumping with NZAS, without saying what had been revealed.
It had monitored the site “in accordance with its consents for many years”, said its chief executive Rob Phillips.
It was now increasing monitoring as part of the government-ordered investigation.
This included beginning the monitoring of groundwater under the SCL storage shed.
NZAS already monitored this and the council had asked for its sampling results, Phillips said.
The council expected to get a report back within a month from consulting environmental engineers Aurecon, and that might lead to even more monitoring, Phillips said.
It would share information publicly where it could, for instance, about the Tiwai groundwater management zone.
The documents also show that engineers recently discovered that sheds containing masses of toxic SCL waste are “structurally weakened”.
This has put a halt “for a few months” to monitoring groundwater around the sheds for contaminants, a December 2020 council report said.
The floor of the first shed built in 1992 cracked almost from the word go. Contaminants have from then till now leaked into barrier membranes in the special foundations, as RNZ reported from previous OIA releases. Four sheds hold in total 75,000 tonnes of the waste, the company has said.
The regional council has consistently praised the smelter’s cooperation on environmental issues over the years.
But now its report lists two issues of “high concern”: The SCL storage pad that it notes is “susceptible to coastal erosion”; and the leachate from the landfill getting into groundwater and Foveaux Strait.
“Some groundwater monitoring bores on the south side of the landfill show some high levels of contamination for a number of contaminants including several nitrogen species and fluoride, and minor levels of heavy metals and polycyclic aromatic hydrocarbons,” it said.
The smelter company said it operated in compliance with all standards set under its resource consents as monitored by Environment Southland and “conducts a range of monitoring, often in excess of those required”. It said it provided reports to Environment Southland every quarter.
Hamilton said the smelter had operated at Tiwai Pt for 50 years and during that time environmental monitoring regimes had evolved.
The company acted immediately to remedy any past non-compliances and will close the smelter in a responsible manner, including removing all spent cell lining from the site, Hamilton said.
The smelter company reports having landfilled 620,000cu m of waste, including cleanfill, but also carbon and dross that contain toxins, and asbestos and hydrocarbon-tainted soil.
It has stockpiled 180,000 tonnes of much more toxic spent cell liner waste, and has exported 58,000 tonnes of it, it said; however, production figures suggest a further 20,000 tonnes of SCL may have been created than accounted for in these figures, and RNZ has queried this with NZAS.
The smelter was allowed to store up to 250,000 tonnes of SCL waste, the city council told RNZ. The European Union describes SCL waste as “carbon-based linings and refractories from metallurgical processes containing dangerous substances”.
The long-term risk is from sea-level rise, with engineers advising the Government the sea will breach the smelter landfill within a century, releasing toxic material that will damage the environment and even kill people. The smelter rejects this advice.