Mine tailings collapse seen as “no longer a threat”


The remediated site at the Tui mine

The major threat posed by the abandoned Tui Mine site at Te Aroha has now been removed with the completed stabilisation of old mine tailings.

Waikato Regional Council Chairman Peter Buckley described the achievement as “a hugely significant milestone”.

“It means there is no longer any risk of the dam made up of old tailings collapsing and sending toxic chemicals down into the Tui Stream and on to nearby fl ood plains.

“I’d like to thank our partners in this project – the Ministry for the Environment, Matamata-Piako District Council, the Department of Conservation and local iwi – for their major contributions and support for this important project.”

Matamata-Piako councillor Phillip Legg said the successful completion of the milestone work in the $16.2 million project was welcome news for the local community.

“Besides removing the threat of a tailings dam collapse, the potential danger from old cyanide drums left in the tailings has also been dealt with after empty drums were located and treated.”

The Tui Mine was an “orphan” contaminated site requiring a major clean up due to the threats it posed. Old mine tailings were dumped at the site behind a geo-technically unstable dam built of the same tailings and local material, thereby blocking a tributary of the Tui Stream and leaching heavy metals into the stream.

If this dam collapsed, the tailings – which contain lead, zinc, arsenic, copper and cadmium – would have contaminated the Tui Stream and nearby land. There were also reports of old drums of potentially deadly cyanide in the tailings – cyanide was used during mining. Now the old tailings have been reshaped and had cement and lime injected into them to stabilise them.

“The result is tailings that have an even, well-drained slope, and the risk of them moving down into the Tui Stream and nearby land has been removed,” said the regional council’s project manager Ghassan Basheer.

“Old drum fragments found have been treated within the stabilised tailings mound and are now be well-buried in the stable old tailings and therefore are not at risk of being exposed.”

By March this year a cap of clean fill is due to have been placed over the newly shaped land. The first stage of landscaping and planting of the site is set to be finished by the end of May.

“We will continue to keep the local community updated on progress,” said Mr Basheer.