Tiwai Point aluminium smelter contamination is significant, report finds

The regional council has asked New Zealand Aluminium Smelters to take a range of steps to address the contamination. Photo / RNZ

Industrial contamination of the environment at Tiwai Point is significant and ongoing and it is unclear what damage has been done to the land, groundwater and the coast, Environment Southland says.

The regional council has asked New Zealand Aluminium Smelters (NZAS) to take a range of steps to address the contamination the company revealed through its own reporting and a subsequent independent assessment.

The council has also now asked for an independent and expanded monitoring programme for the site.

Environment Southland chief executive Wilma Falconer said the council wanted people to be confident in both the work under way to address the site's impact on the environment as well as the planned remediation of the site after the smelter's closure.

With any industrial operation of a scale similar to the operation at Tiwai Point some level of contamination was to be expected, Falconer said.

"However, it is evident from the data supplied by NZAS that a significant mass of contamination has been discharged into the environment.

"What this data doesn't tell us is whether the historic and current NZAS operations have had, or are causing, negative effects to the land, groundwater and coastal marine environments."

As part of the council's work programme to understand the extent and impact of contamination at Tiwai Point, it asked EHS Support, a consultancy with international experience in decommissioning smelters, to assess the company-commissioned site investigation report.

The consultants' assessment of the company data showed gaps in its data including information relating to its landfill, spent cell liner pad and the wider environment.

It did though reveal pollutants in groundwater, drains and soil. There was surface soil concentrations of PAHs (polycyclic aromatic hydrocarbon) and fluoride above health risk criteria and ecological screening criteria.

Groundwater was contaminated with elevated levels of fluoride, aluminium, arsenic, PAHs, and cyanide.

Stormwater drain sediment contained elevated levels of fluoride, aluminium, PAHs, and heavy metals.

The chemical contamination was found in concentrations above generic risk-based criteria, above commercial-industrial and recreational health-risk criteria, and above ecological screening criteria.

There were also indications contaminants from storage and other infrastructure could be escaping into the surrounding environment, the consultants said.

Falconer said the council was now clearer about the work required to understand the extent of the contamination and to ensure historic and ongoing production waste was well managed, before and when the smelter closes.

She said the company had been working co-operatively with the council, providing access to the site and making improvements in housekeeping.

The data that was in the company-commissioned site investigation was an important contribution to the council's work programme, she said.

The company would also soon begin drilling around 50 new bores to monitor groundwater and hydrology on the site.

It had already expanded its testing and provided updated information on ouvea stored around Southland.

Completion of remediation for unauthorised discharges of contaminants to land or water relating to fluoride contamination at two sites was required later this month.

And further monitoring results were due soon.

After the consultants' review of the company data, the council asked NZAS to prepare a waste-stream management plan that outlined how and where the various types of the company's waste was disposed of.

It also asked for access to the site for an independent and expanded contaminant monitoring programme that included the landfill, spent cell liner pad and coastal marine area.

Falconer said presently, monitoring was done by NZAS.