The
Tui Mine is located near Te Aroha at the base of the Coromandel Peninsula. It was a lead-zinc mine, which
closed in 1973 due to declining concentrate prices, high overheads, and high
mercury levels in the ore. The site was abandoned, leaving behind an acid rock
drainage generating system, including a sulfide-rich tailings dam which has
since caused pollution of Tui Stream, as well as open adits and waste piles
which drain predominantly into the neighbouring Tunakohoia Stream. At the AusIMM
conference in 2003, Harvey and Webster-Brown presented water quality results
from the Tui mine site and lower stream catchments in 2002. In April 2006,
Environment Waikato undertook remediation works
to stabilise the dam and reduce acid drainage entering Tui Stream. In this
study, water quality results from the Tui mine site and lower stream catchments
are again being determined, in order to compare with the pre-remediation
results. Preliminary data collected for summer indicate a minor but consistent
improvement in water quality in the lower stream catchments, although lower Tui
Stream continues to exceed ANZECC (2000) aquatic life guidelines for Cd, Cu, Pb
and Zn. This slight improvement may be due to a decrease in the flow of ARD into
Tui Stream, as there does not appear to have been an improvement in quality of
the contributing ARD waters.