Mining and Sustainable Development II - DTIE

Mining
despite great improvements, there has been a
reported failure of a tailings dam almost
every year for the past two decades. The
damage caused by these failures in terms of
human casualties, destruction of property,
disruption of communications, pollution of
the environment and economic loss to the
mining industry is enormous. The purpose
of this Bulletin is to discuss some of these failures
and see what lessons can be learned from
them, to identify improvements that would
reduce the occurrence of these failures.”
Knowledge about the factors that control
the behaviour of tailings dams has
improved greatly during the past 20
years. Detailed guidelines for the safe
design and construction of tailings dams
and waste lagoons have been published
and the consequences and public awareness
of tailings dam failures have increased considerably,
causing managers and owners to
become more aware of the risks involved in the
construction of impoundments. Nevertheless,
although the percentage of recorded failures has
decreased over the past decades because of the
improved understanding of the behaviour of dams
and the improved methods of design and construction,
the number of incidences (14 between
1990 – 2000) remains unacceptably high. Many
factors influence the behaviour of tailings
impoundments; accidents and other incidents are
often the result of inadequate site investigation,
design, construction, operation, or monitoring of
the impoundment, or some combination of these.
At the design stage, attention must be paid to
those critical features that can affect the long term
safety of a tailings dam. Sound fundamental
design pays dividends throughout the life of the
dam. ICOLD and others have published many
technical guidelines for the safe design and construction
of tailings dams and waste lagoons.
However, ICOLD is increasingly warning that to
keep a tailings facility in a safe condition throughout
its life, overall management and the practical
application of knowledge is critical. Sound design
must be followed by appropriate management,
plus regulation that effectively targets ongoing
operational safety over the life of the facility – and
beyond.
ICOLD and UNEP have drawn the conclusion
Venezuela: environmental damage from artisanal mining activity
from recent accidents that the vital efforts on prevention
must be supplemented by additional
attention to risk reduction and mitigation to
reduce not only the frequency, but also the severity
of accidents which do occur. Emergency preparedness
should also be part of the total picture
of responses to the continuing contemporary
accident record.
Every site and dam is unique and there
needs to be more attention paid to risk
assessments in each individual case, leading
to tougher decisions about whether
the presence of certain risk factors can be
adequately addressed through siting or
design or other means. UNEP has posed
the question as to whether in some cases
there may also be scope for incorporating
additional measures through engineering,
siting or contingency structures, to reduce
the energy or deflect the impact in the
event of a failure.
The Bulletin on Lessons Learned is
intended to give advice, drawn directly
from experience, that can help those
responsible for impoundments and tailings
dams. Learning from errors is vital for
improving knowledge and promoting improvements
and it is in that spirit that the Bulletin will
be published early in 2001. It is only one in a series
of initiatives being taken in the tailings area with
the aim of making a difference to their safety and
environmental record.
◆
Silvaculture project for area rehabilitation: Las Cristinas, Venezuela
UNEP Industry and Environment – Special issue 2000 ◆ 67