New Zealand Aluminium Smelters is exploring options to export more of the toxic waste it has stockpiled at Tiwai Point.
The news comes just days after Environment Southland announced it would increase testing and monitoring at the smelter site to determine what environmental remediation will be required when the smelter closes.
NZAS chief executive and site general manager Stew Hamilton said there was a total of 181,000 tonnes of spent cell liner, known as SCL, on site.
Hamilton said 106,000 tonnes was stored on a purpose build concrete pad with a special drainage system to capture and treat any run-off and 75,000 tonnes are in purpose built, weatherproof buildings on site.
On Monday, RNZ reported that a storage building floor cracked in 1995 and contaminants including cyanide, fluoride and ammonia had had to be pumped out.
In response to those claims, an NZAS spokesperson said the cathode storage building was purpose built with layers of sand and impermeable membranes beneath a concrete floor. When the report referred to decreasing cyanide and fluoride levels it was referring to levels contained within the building foundations.
“In short the building did exactly what it was designed to do,’’ the spokesperson said.
Hamilton said the company was carefully storing the waste produced by our aluminium smelter at Tiwai Point.
“It is extremely closely monitored, as is the coastal erosion on the Peninsula. We are confident the waste material is securely and safely stored while we work on the best end user solution,’’ he said.
SCL is the waste lining of cells used in the smelting process, which have been rebuilt. When stored correctly it is safe and does not release gases.
A NZAS spokesperson said for SCL to release gas and become explosive, four things must occur simultaneously and none of them can occur at NZAS under the current storage conditions: it must become wet, it must be in an enclosed area which is not ventilated, there must be a source of ignition, and the gas levels must be within a concentration range which enables combustion.
SCL is often used in cement making, but there are no cement manufacturers in New Zealand able to take the material, he said.
“As part of our detailed closure study we are exploring other options and in particular would hope to find a local end user. We don’t have all the answers right now, but we are working hard to ensure we deliver the best result in the end.
The best solutions can sometimes take time and in the meantime we know the material at Tiwai, as confirmed by WorkSafe inspectors who visited in late February, is safe and well monitored.”
“Around 58,000 tonnes has been exported over the past decade to end users overseas however as part of our closure study process we are exploring options to increase this rate.’’
A WorkSafe spokesperson said it conducted an assessment visit, which was a formal and structured process, and enforcement action could be taken should breaches be identified.
The visit was not a WorkSafe investigation and should not be referred to as such, the spokesperson said.
“We are satisfied that the product is stored and contained appropriately. We requested some additional information about processes for monitoring and are still waiting on this. It is not unusual for WorkSafe to ask for further information during the course of an assessment.
“No enforcement has been issued at this point.’’
Environment Southland was asked to undertake further environmental monitoring at Tiwai Point by Environment Minister David Parker, to assist the Government to determine the extent of the remediation required at the site once NZAS closes.
The Government has given the regional council $300,000 of funding to engage external expertise as part of its monitoring strategy.
Last month Ministry for the Environment said it was unclear whether Rio Tinto is under any legal obligation to remediate the site of its smelter at Tiwai Point after it closes in 2024.
Ministry for the Environment chief executive and Secretary for the Environment Vicky Robertson told the Environment Select Committee that the legal liability for Rio Tinto to remediate the site once the smelter closed had been ‘’difficult to pin down”.
*Original article online at https://www.stuff.co.nz/environment/124469518/nzas-looks-to-export-toxic-waste-stockpiled-at-tiwai-point