Above: Recreation is an organic activity around any water body;
and pit lakes and picnics need be no exception
Left page: Hard rock pit lakes in Western Australia
are often very deep and steep sided; bearing little
resemblance to natural water bodies in the state
Below: The high numbers of lakes in semi-arid and
desert areas demonstrate that Western Australian
pit lakes are not restricted to high rainfall areas
Mine closure is not new to the mining industry
internationally or inWestern Australia; however, regulations
and social expectations increasingly address the pit lakes
that remain at the completion of mining operations.
Pit lakes of unrehabilitated mine sites may often
have ramps still leading into them; convenient access for
opportunistic local swimmers or thirsty wildlife. Human and
stock/wildlife safety, driven by pit wall access and stability
are therefore initial rehabilitation issues, combined with
water quality as long-term drivers of closure requirements.
A simple way to often avoid pit lake problems is to backfill
them. Reasonably simple, this approach may face difficulties
of insufficient backfill volumes available in low waste ore
operations such as iron and coal, and the inevitable resource
sterilization against further mining opportunity. Altered
groundwater flow direction and quality may also result.
Coal mining legacy pit lakes in regions such as the Collie
Coal Basin are being well used as stopover points by ‘grey
nomads’ and other tourists. A burgeoning pit ‘Lake District’
is evolving with 13 lakes currently and the prospects
of more lakes in the future, as a century of current coal
resources are developed. Lakes here provide social end-
use opportunities at mine completion including aesthetics,
water skiing, swimming, fishing and camping. They also
provide a valuable further source of tourism income to the
shire and community. Established international examples
show us that carefully planned development of these end-
uses go a long way to aiding lease relinquishment at mine
completion, due to the strong community support these
initiatives can generate.
Other Western Australian mining regions that are remote
and away from established communities are not likely to
have the same opportunities for such end-uses. Nevertheless,
wildlife habitat is expected to play a key role in these new
amphibious landscapes. Declining rainfall across most of
the state coupled with historical and increasing demands on
natural water bodies, such as wetlands and rivers, means
aquatic habitat is a crucial environment for maintaining
state biodiversity. ‘Ecological’ engineering of pit lakes to
provide surrogate aquatic habitats as wetlands or lakes
has been shown to help offset previous mining activity
impacts and create a positive environmental legacy once the
resource is gone.
The future for mining is bright in Western Australia, and
so are the potential benefits for operators, communities and
the environment when mine closure explicitly considers pit
lakes in planning.
The challenge now is to consider how we can best
address the pit lake landforms that historically remain and
will be developed in the future; and how we can make the
most of the opportunities they equally afford companies in
achieving social and environmental sustainability goals.
MINESITE 2012
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