The Tui
mine site is situated on the NW flank of Mt. Te Aroha, at approximately 400 m
altitude. During underground mining operations two lead-copper-zinc ore bodies
were exploited and processed on site. The legacy of the mining operation is a
barren dam containing over 100 000 mm of sulphide-rich tailings. The Tui mine
site is arguably the worst case of environmental degradation resulting from past
mining activity inNew Zealand.
Although the impacted area (approximately 4 ha) is extremely small by
international standards, acid mine drainage (AMD) emanating from the abandoned
tailings dam and mine adits has severely contaminated local streams and
prevented natural plant recolonisation of the site for more than 20
years.

The
suitability of the tailings as a potential plant growth
medium was assessed with the end view of revegetating the tailings dam and
alleviating AMD. This paper outlines characterisation work conducted on the tailings
and summarises preliminary results from plant growth trials. The tailings
contain up to 5% Fe, 1.15 % Pb, and 0.45% Cu in the form of sulphide minerals.
The distribution of heavy metals, sulphate and total sulphur with depth
indicates that the top 200 - 300 mm of
the tailings have been extensively weathered since their deposition. The
oxidation of sulphide minerals, particularly pyrite (FeS2 )
has reduced the pH of the tailings to nearly2 in places. Below 300 mm the sulphide
minerals are largely unweathered and the theoretical acid generating potential
of the tailings exceeds 170 Mg CaCO3/1000 Mg tailings at certain
depths. Plant growth trials were conducted to study the effects of lime and
organic matter addition on the establishment of vegetation on the Tui mine
tailings. Several plant species were assessed including some cultivars bred for
their tolerance of heavy metals.