The Tui mine is an abandoned mine on the western slopes of Mount Te Aroha

Te Aroha

Te Aroha is a rural town in the Waikato region of New Zealand with a population of 3,768 . It is 53 km northeast of Hamilton and 50 km south of Thames. It sits at the foot of 952-metre Mount Te Aroha, the highest point in the Kaimai Range....

 in the Kaimai Range of New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

. It is considered to be the most contaminated site in the country, following the clean up of the former Fruitgrowers Chemical Company site at Mapua

Mapua, New Zealand

Mapua is a small town in the South Island of New Zealand.It is to the west of Nelson on State Highway 60 and on the coastline of Tasman Bay. The 2006 census gave a population of 1878, up 16.1 percent since the 2001 Census.:...

, Nelson.

History

In the 1960s, the Tui mine extracted copper, lead and zinc sulphides. The mine was abandoned in 1973, after the mining company Norpac Mining went bankrupt. Waste, rock ore dumps and mine tailings

Tailings

Tailings, also called mine dumps, slimes, tails, leach residue, or slickens, are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore...

 were left behind. The tailings have significant amounts of zinc and cadmium. The mine tailings are stored behind a dam in a large pool-like area which has an oxidised, solid surface layer.

Environmental issues

The tailings dam is considered to be unstable and is leaching various minerals, including heavy metals, into neighbouring waterways and this adversely affects the stream ecology

Ecology

Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

. According to Environment Waikato, the Tui mine has three major environmental impacts;

1. The heavy metals lead and cadmium are leaching from the tailings dam into the Tunakohoia stream, which flows through land managed by the Department of Conservation and through the centre of the town of Te Aroha
   Te Aroha
   Te Aroha is a rural town in the Waikato region of New Zealand with a population of 3,768 . It is 53 km northeast of Hamilton and 50 km south of Thames. It sits at the foot of 952-metre Mount Te Aroha, the highest point in the Kaimai Range....
   
   
2. The separate Tui catchment is also contaminated with heavy metals from the tailings dam;
3. The abandoned mine tailings dam in the Tui catchment is at risk of collapsing in a moderate seismic event or an extreme weather event. That could cause 90,000 cubic metres of mine waste to liquefy and to flow down the Tui stream near to Te Aroha.

Remediation

In 2007, the New Zealand Government announced that $9.88 million will be made available to clean up the site with the work scheduled to be completed by 2010. In April 2010 it was reported that the estimated cost of the clean-up would be $17.4 million and in 2011 a sum of $16.2 million was allocated to the cleanup with most of the funding from central government.