The Tui mine is an
abandoned mine
An abandoned mine is a mine or quarry which is no longer producing or operational and, there is no responsible party to finance the cost to address the remediation and/or restoration of the mine feature/site. Terms and definitions vary though th ...
on the western slopes of
Mount Te Aroha
Te Aroha ( mi, Te Aroha-a-uta) is a rural town in the Waikato region of New Zealand with a population of 3,906 people in the 2013 census, an increase of 138 people since 2006. It is northeast of Hamilton and south of Thames. It sits at the f ...
in the
Kaimai Range of
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...
. It was considered to be the most
contaminated site
In urban planning, brownfield land is any previously developed land that is not currently in use. It may be potentially contaminated, but this is not required for the area to be considered brownfield. The term is also used to describe land prev ...
in the country, following the cleanup of the former Fruitgrowers Chemical Company site at
Māpua, Nelson.
History
In the 1960s, the Tui mine extracted
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...
,
lead
Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
and
zinc sulphides.
[ ] The mine was abandoned in 1973, after the mining company Norpac Mining went bankrupt.
Waste, rock ore dumps and mine
tailings
In mining, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction ( gangue) of an ore. Tailings are different to overburden, which is the waste rock or other material that overl ...
were left behind. The tailings have significant amounts of zinc and
cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
.
The mine tailings are stored behind a dam in a large pool-like area which has an oxidised, solid surface layer.
The dam contains over 100,000 cubic metres of very acidic, sulphide-rich tailings. In 1997, there had been no natural plant recolonisation on the tailings for more than 20 years.
Environmental issues
The tailings dam was considered to be unstable and is leaching various minerals, including heavy metals, into neighbouring waterways and this adversely affected the stream
ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...
. According to Environment Waikato, the Tui mine had three major environmental impacts;
# The heavy metals lead and cadmium were 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 ( mi, Te Aroha-a-uta) is a rural town in the Waikato region of New Zealand with a population of 3,906 people in the 2013 census, an increase of 138 people since 2006. It is northeast of Hamilton and south of Thames. It sits at the ...
. Four years after the mine closed, the Te Aroha town water supply was found to be contaminated with heavy metals leaching from the tailings.
# The separate Tui catchment was also contaminated with heavy metals from the tailings dam.
# The abandoned mine tailings dam in the Tui catchment was at risk of collapsing in a moderate seismic event or an extreme weather event. That could have caused 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
, background_color = #012169
, image = New Zealand Government wordmark.svg
, image_size=250px
, date_established =
, country = New Zealand
, leader_title = Prime Minister Jacinda Ardern
, appointed = Governor-General
, main_organ =
, ...
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. Remediation of the mine site was completed in 2013, at a total cost of $21.7 million.
See also
*
Mining in New Zealand
Mining in New Zealand began when the Māori quarried rock such as argillite in times prior to European colonisation. Mining by Europeans began in the latter half of the 19th century.
New Zealand has abundant resources of coal, silver, iron ore, l ...
*
Environmental issues in New Zealand
The environment of New Zealand is characterised by an endemic flora and fauna which has evolved in near isolation from the rest of the world. The main islands of New Zealand span two biomes, temperate and subtropical, complicated by large mount ...
References
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Environmental issues in New Zealand
Te Aroha
Underground mines in New Zealand
Environment of Waikato
Tailings dams