A $22.5 million government-funded project to clean up New Zealand's worst contaminated site is now complete.

A closing ceremony was held at Tui Mine at Te Aroha to mark the successful conclusion of the five-year project this week.

A $22.5million government-funded project to clean up Te Aroha's Tui Mine is complete.

'Tui Mine posed a real safety and environmental risk for the Te Aroha community for many years, so it is extremely satisfying to complete the project,” says Environment Minister Amy Adams.

The Government committed $21.5million to the clean-up.

Together with money provided by Waikato Regional Council and Matamata-Piako District Council, this formed a joint fund of $22.5million.

'The financial contribution from the Government is the largest ever for a clean-up and it shows our commitment to improving management of the environment.”

The mine opened in 1967 to extract metals, including copper, lead and zinc, but it was abandoned in 1975.

Left behind were waste rock and ore dumps, tailings and the ruins of the mine workings. These leached heavy metals and acid into the Tui and Tunakohoia Streams.

In addition, there was a risk the tailings mass would liquefy in an earthquake or fail in an extreme weather event and flow down the mountain, says Amy.

Since the clean-up began, the tailings dam has been stabilised and 110,000 cubic metres of old mine tailings have been treated and stabilised.

She says the water quality of the Tunakohoia stream has improved and there is no longer a threat to human health.

The on-going monitoring and maintenance of the Tui Mine will lie with the Department of Conservation and Matamata-Piako District Council.

The site will initially be covered in grass, and then shrubs, until it is eventually left to naturally regenerate.