Seismic risk assessment for oil and gas pipelines - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 681

no signifi cant consequence without detailed calculation. Unfortunately,
defi ning tolerable risk is often complicated by emotional issues related to
explicitly defi ning an acceptable likelihood for injuries or deaths. Examples
of acceptable risk levels adopted by various industries and organizations
are provided in Table 25.2.
The second step is to defi ne the potential hazards to pipelines in question
and determine the likelihood of those hazards occurring. These are expected
to include pipe damage from ground displacement (e.g., landslides, liquefac-
tion, and settlement), pipe damage from third party activity, and pipe
damage related to typical operational conditions (e.g., Kiefner and Trench,
2001). In many countries, regulators require oil and gas pipeline operators
to report signifi cant pipeline accidents and this information can provide the
basis for estimating the likelihood of hazard occurrence. In some cases,

Table 25.2 Examples of acceptable annual probabilities

Annual
exceedance
probability
(AEP) Reference 1/AEP

Need for accident planning unwarranted or
unnecessary except for catastrophic accident 1

0.001000 1 000

Point for diminishing justifi cation for reducing US
Bureau of Reclamation dam failure 2

0.000100 10 000

California gas transmission pipeline incident rate
(1984-2001) 3

0.000074 13 513

Building collapse from seismic load (US) 4 0.000040 24 750

Highest safety class for nuclear processing facilities 5
DNV OS-F101 lowest failure probability for high risk
of human injury 6

0.000010 100 000

Equivalent annual probability of earth impact by
asteroid Apophis in 2036 7

0.000004 250 000

Lower range of probability for core damage to
existing nuclear power plants 8

0.000002 500 000

Estimate of lower range of probability for core
damage for proposed new nuclear power plants 8
Acceptable individual risk for student established by
California Department of Education 3

0.000001 1 000 000

1 FEMA/DOT/EPA (1988).
2 US Department of Interior (1997).
3 California Department of Education (2007).
4 ASCE 2010 (assumes Risk Categorgy 2 and annual probability of MCE of
1/2 475).
5 Kennedy (1992).
6 Det Norske Veritas (2000).
7 NASA (2009).
8 Nuclear Energy Institute (2012).