Environmental Assessment
Volume E-3.6
Tailings Facility
Natural Risks
Ambatovy Project
41
January 2006
3.6.4
Issue Scoping
A natural hazard was defined in the risk assessment (Knight Piesold 2005b) as a
naturally occurring event that could lead to potential failure that would impact
downstream resources. Three principal natural hazards are identified as seismic,
hydrological and geotechnical and the issues associated with each are
summarized as follows. All the issues identified from stakeholder consultation
were also included in these hazard scenarios (Volume A, Section 6).
Seismic Hazards
Ground motions from an earthquake could trigger:
•
A landslide in the watersheds of the tailings ponds which could cause
overtopping or breaching of the embankments.
•
Liquefaction of the tailings, embankments and/or foundation which
could cause overtopping or breaching of the embankments.
•
The creation of a tsunami due to an off-shore earthquake which could
travel inland and damage the embankments.
Hydrological Hazards
Heavy rains or high winds from a large precipitation event or cyclone could
trigger:
•
A landslide in the watersheds of the tailings or water basins which could
cause overtopping or breaching of the embankments.
•
Inundation of the tailings or water basins where the overflow spillways
would pass the maximum designed flows in a safe and controlled
manner. This would cause flooding downstream of the tailings facility.
•
Inundation of the tailings or water basins where the overflow spillways
could not pass the storm flows in a safe and controlled manner. This
could cause overtopping or breaching of the embankments.
•
Erosion and failure of the embankments which could cause release of
tailings and/or process water to the environment.
•
The creation of a large wave from high winds that could overtop or
breach the embankments.
