Was the Environmental Assessment Adequate? - Mining and the Environment: From Ore to Metal - page 509

the rivers would transport the wastes to the sea. In both these projects, the unplanned deposi-
tion of tailings occurred on land outside the river channels, causing widespread loss of forest.
In both cases, modelling had predicted that the carrying capacity of the rivers would not be
exceeded. Clearly, something was wrong with the model or, more likely, on the assumptions
that were used or the input data. Any project should be aware of the possibility that some-
thing will go badly wrong, and should be prepared to respond rapidly in such an eventuality.
Clearly, a well-designed audit programme is the key to identifying impending problems so
they can be remedied before causing damage. However, experience has shown that nasty sur-
prises will still occur.
In the experience of these authors, the most common causes of unpredicted impacts
relate to what might be termed 'system overload'. For example the mill throughput may
be increased beyond its design capacity, which may result in the assimilative capacity of the
receiving environment being exceeded. Similarly, a tailings storage facility may be designed
to contain a certain volume of tailings, but during operations, more ore is mined than antici-
pated and the embankment is raised to accommodate the additional tailings. In some circum-
stances, this could lead to failure. It is therefore most important that any changes to a project
be thoroughly assessed in terms of their potential environmental consequences. This applies
whether or not such additional assessments are required under host country regulations.
Other causes of unpredicted impacts are:

The most common causes of
unpredicted impacts relate to
what might be termed 'system
overload'.

●

Inadequate baseline data, such as insufi cient number or frequency of samples to ade-
quately represent the range of variability;

●

Failure to identify all impacts. On several projects, for example, the risks of acid rock
drainage (ARD) from the mine, waste rock and tailings, were adequately predicted
while other sources of ARD, such as access roads exposing acid-generating material,
were not considered; and

●

Human error, sometimes due to complacency after many years of trouble-free operation.

Again, a well-designed audit programme should identify and highlight the potential for
such impacts, before they develop.

REFERENCES

ADB (2000) Special evaluation study on the policy impact of involuntary resettlement.
Manila. Available: www.adb.org/Documents .
IFC (2006) Environmental and Social Performance Standards, International Finance
Cooperation, www.ifc.org .
Sadler (1996) International Study of the Effectiveness of Environmental Assessment,
Final Report Environmental Assessment in a Changing World: Evaluating Practice to
Improve Performance. Canadian Environmental Assessment Agency and International
Association for Impact Assessment.
UNEP (2002) UNEP Environmental Impact Assessment Training Resource Manual,
Second Edition, www.unep.ch/etu/publications/EIAMan_2edition_toc.htm .
World Bank (1989) Operational Directive 4.01 on Environmental Assessment, converted in
1999 into a new format: Operational Policy (OP) 4.01 and Bank Procedures (BP) 4.01.
World Bank (1989) Base Metal and Iron Ore Mining, Industry Sector Guidelines, Pollution
Prevention and Abatement Handbook.
World Bank (2001) Operational Policy OP 4.37 Safety of Dams.

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