Smelter site remediation plan unveiled

THE company in charge of the Tiwai Point smelter, which is set to close in 2024, has acknowledged it could have done better in the past and yesterday made public its initial plan for remediation of its site.

Rio Tinto aluminium closure readiness general manager Nicole Atherton said the company commissioned a report to guide its remediation work.

Given it had been a heavy industrial site for more than 50 years, it expected some areas would need remediation.

‘‘This indepth analysis by GHD provides the critical information to do this work accurately and effectively, which includes addressing instances of contamination.’’

Samples were taken from 238 locations across the smelter site and surrounding area. The investigation found 83% of groundwater samples exceeded New Zealand drinking water standards guidelines and Environment Southland groundwater rules.

The standards were used as a comparison, and the exceedances were mostly for aluminium and fluoride with a lower number of exceedances for arsenic, iron and pH.

Five E. coli samples were analysed, and all five had concentrations above the standards.

Groundwater testing results showed levels above guidelines for drinking water, but no drinking water was drawn from areas where contamination was found, the company said.

‘‘Further sampling is needed throughout various seasons to understand compliance against [the rules] and the potential impact of these findings.’’

All soil samples taken from outside the smelter’s footprint across the wider Tiwai Peninsula met the criteria for both industrial and recreational land use, it said.

The investigation also found 1% of the soil samples did not meet the criteria for commercial industrial land use and 9% did not meet the criteria for recreational land use.

The samples which did not meet the criteria were mostly taken from 10cm below ground level, meaning it could be remediated.

This did not pose a risk to human health unless the soil was disturbed, which would only occur under strict supervision and require a special permit, a press release said.

Ms Atherton said the company was working with both GHD and Environment Southland to finalise the sampling plan.

“We have committed to removing all spent cell lining, managing waste and to remediating the site and will continue working closely with Ngai Tahu, Environment Southland and the Ministry for the Environment.

“We recognise some waste has been handled poorly in the past and this was not acceptable . . . We are working to significantly improve our performance.’’

She understood the results might cause concern and encouraged anyone with further questions to email NZAS.Enquiries @riotinto.com.