A guide to leading practice sustainable development in mining

For in-pit tailings deposition, tailings slurry is pumped and discharged into one of
a number of mined out pit voids. Process water is recovered from pits and reused
through the process circuit. The tailings slurry is pumped at 60 percent solids and
contains 130 milligrams per litre WAD cyanide at the process plant. Without adequate
controls, the WAD cyanide levels may pose risks to wildlife and groundwater quality.
The Tanami region sits within the east Asian-Australasian flyway for migratory
shorebirds. Daily bird checks conducted on the Granites lease since early 2005
have detected 12 of the 43 species listed in the 1993 National Plan for Shorebird
Conservation in Australia. A further three species are likely to be found in the area
during migration but have not been sighted on the lease. The Newmont Standard for
Tailings Management states that tailings activities will not impact on groundwater.
There are potential environmental impacts associated with in pit tailings deposition
in the Tanami including fauna mortalities associated with cyanosis and groundwater
contamination. The water surrounding Bunkers Hill pit has been found to range
from brackish to saline. The deposition of tailings into Bunkers Hill pit will probably
result in a saline plume infiltrating the surrounding bedrock and being detectable
for up to 250 metres from the pit. Tailing into Bunkers pit commenced in June
2007 and to date, groundwater contamination has only been detected in one
seepage interception bore. As yet there is no evidence of connectivity between the
surrounding groundwater and the pit in the other seepage interception or monitoring
bores. This may change as the tailings rises in the pit, therefore, the bores are
routinely monitored (see LP Cyanide p.60).
It is believed that the potential impacts can be managed by implementing cyanide
destruction technology, installing a seepage interception system, and with diligent
operational management and monitoring.
Figure 4.6 – Inpit tailings disposal at the Tanami
An international example of leading practice in a range of areas including cyanide,
tailings disposal and general environmental management is the Chatree gold mine in
Thailand which is ranked as the safest mine in the world, a remarkable achievement
for a mine in an emerging economic region.
A GUIDE TO LEADING PRACTICE SUSTAINABLE DEVELOPMENT IN MINING 103