Introduction

The Tui Mine is an abandoned mine site. It was once dubbed New Zealand’s most contaminated site. But after five years of remediation work it is no longer a health and safety risk to the local community and environment.

It is located on the western flanks of Mt Te Aroha in the Kaimai range and is surrounded by public conservation land in the Kaimai Mamaku Forest Park.

Contamination from the mine

The mine's water runs straight down the blasted cliff face to join the Tunakohoia Stream.
The mine's water runs straight down the blasted cliff face to join the Tunakohoia Stream

The mine produced a range of base metals, including copper, lead and zinc from 1966 to 1973, when it was abandoned by Norpac Mining Company.

Two streams flow from the mine site through the township of Te Aroha. The Tunakohoia stream was affected by heavy metals leaching from the adits and tailings dam and the Tui stream was affected by heavy metals arising from the tailings dam and the abandoned mine tailing impoundment.

The tailings dam was found to be at risk of collapse in a moderate seismic event or an extreme weather event. If an event had occurred, over 90,000 m3 of mine waste could have flowed down the Tui stream through part of the township of te Aroha and into the Waihou river that feeds into the Hauraki Gulf.

Remediation project

The Tui Mine remediation project aimed to:

  • contain the tailings within a stable and secure location
  • reduce the release of contaminants into the Tui and Tunakohoia streams, thereby improving the water quality in those streams
  • improve the geotechnical stability of the tailings impoundment
  • improve the safety and security of the site
  • improve the visual appearance and aesthetics of the site
  • address as far as practicable, within the limitations of the project, the impacts of the Tui mine on the taonga of the Te Aroha maunga (Mt Te Aroha) for iwi.

A concrete hopper at Tui Mine.
Remains of the mining operation include this concrete ore hopper and other earthworks

The project was completed in two phases:

  • Phase 1 involving the preparatory work including, design, site establishment and the treatment of old underground mine workings.
  • Phase 2 involved remediating the tail tailings dam area. A one metre cap of clean fill was placed over the tailings dam to stop oxygen and water entering the stabilised tailings.

Initial planting of native shrubs at the sites old processing plant was carried out in 2013 by volunteers from the local community.

The project was overseen by a governance group comprising of the Waikato Regional Council, Ministry for the Environment, Matamata-Piako District Council, the Department of Conservation and local iwi. A steering group including representatives from the partner agencies and iwi oversaw the projects implementation.

Both the District Council and the Department of Conservation will be responsible for ongoing maintenance and monitoring but tests have already shown excellent improvement in the ecological health of both the Tunakohoia and Tui streams.

Success story

160,000 man hours of planning, management, engineering and construction time plus $21.7 million dollars were invested into the project.

This is a great success story for the environment. It also shows the success that comes from partnerships with central, regional and local government agencies working with iwi and the community to help heal the maunga of Te Aroha.

The success of the project was acknowledged with the collective agencies winning the projects category at the Resource Management Law Association awards.


Related link

Tui Mine on Waikato Regional Council website

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