Environmental Assessment
Volume C-3.5
Slurry Pipeline
Natural Risks
Ambatovy Project
43
January 2006
the land containing the pipeline platform and pipeline. Either movement, if large
enough, could cause a pipe failure.
Water Erosion
During rainfall events, water soaks into the ground increasing the risk of
landslips and/or landslides. When the ground is saturated, water runs across the
surface to local low spots which usually drain to an area waterway.
The selected pipeline route crosses many streams and rivers as well as dry
valleys that could become flooded during rainfall events. There is a risk at each
of these crossings that erosion during a rainfall event damages the pipe. The
damage could be caused by undermining supports for an aerial crossing,
exposing a buried crossing, or widening the waterway exposing pipe outside the
waterway. The exposed pipe may fail due to pressure of the flowing water, lack
of adequate support (lost support in aerial crossing), or damage from rocks and
debris moving in the river.
Seismic Hazards
There are three major events that could damage a pipeline during a seismic event:
•
Significant land shift at a specific fault could shear the buried pipeline at
the point of crossing the fault.
•
Liquefaction of the soil containing the pipeline during an earthquake
eliminates the support causing the pipeline to sink into the earth. This
could overstress the pipeline to the point of failure.
•
Land/rock fall could occur dropping material onto the pipeline right-of-
way. This event would be similar to a land slide event discussed above.
The impact (and mitigation methods) are the same.
The key question for natural hazards is:
Key Question TG-1
Are the Risks of Natural Hazards to the Public
and Environment Increased as a Result of the
Pipeline?
3.5.5
Impact Assessment
3.5.5.1 Assessment Methods
A risk assessment was completed for natural hazards (PSI, 2005) using a
qualitative estimate based on worldwide pipeline experience. For each of the
