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Geotechnical News December 2010
Tailings Dam Failures: A Review of the
Last One Hundred Years
Shahid Azam
Qiren Li
Introduction
Tailings dams are some of the largest
earth structures geotechnical engineers
construct. These embankments are often
built with steep slopes using the coarse
fraction of the tailings thereby saving
on cost. To keep such impoundments
standing is one of the most challenging
tasks in mine waste management.
Generally, these containment facilities
are vulnerable to failure because of the
following reasons: (i) dyke construction
with residual materials from the mining
operations; (ii) sequential dam raise
along with an increase in effluents; (iii)
lack of regulations on design criteria,
especially in developing countries;
and (iv) high maintenance cost after
mine closure (Rico et al., 2007). For
a world inventory of 18401 mine
sites, the failure rate over the last
one hundred years is estimated to be
1.2%. This is more than two orders of
magnitude higher than the failure rate
of conventional water retention dams
that is reported to be 0.01% (ICOLD,
2001).
The mining industry has experi-
enced several significant dam failures
in recent history: Merriespruit (South
Africa), 1994; Omai (Guyana), 1994;
Los Frailes (Spain), 1998; Baia Mare
(Romania), 2000; and Aitik (Sweden),
2000. An acute societal concern over
such events has resulted in enforc-
ing stringent safety criteria at mining
operations in some parts of the globe.
However, the standard of public report-
ing varies considerably from country to
country and from region to region. A
large number of tailings dam failure in-
cidents remain unreported or lack basic
information when reported. This has
seriously hindered the development of
safety regulations in such areas. De-
spite insufficient data, a generalized
statistical analysis is exigently needed
to help minimize tailings dam failure
events.
Scope of this Study
A comprehensive worldwide database
for all historical failure events is
virtually inexistent. Still, a number of
databases can be used in conjunction.
The primary databases are given
as follows: (i) United Nations
Environmental Protection (UNEP); (ii)
International Commission On Large
Dams (ICOLD); (iii)World Information
Service of Energy (WISE); (iv) United
States Commission On Large Dams
(USCOLD); and (v) United States
Environmental Protection Agency
(USEPA). Even these databases should
be considered as subsets of the actual
number of tailings dam failure incidents
in the world. Nonetheless, this article
attempts to statistically analyze the
available data on tailings dam failures
by dividing the failure events into two
time groups, namely: pre-2000 events
and post-2000 events.
A total of 198 pre-2000 events and
20 post-2000 events were identified.
Among the former, 147 and all of the
post-2000 events contained enough in-
formation to help conduct the analyses.
A significant portion of the reported
failures had to be categorized as “un-
Figure 1. Failure events over time.
