Page 361 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

15/336 Risk Management

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Minimum Number of Fatalities
Figure 15.1 FN curve.
Both societal and individual risks, when derived from a unit- tions that estimate a hazard radius from a pipeline failure to be
length risk value, will be highly sensitive to the length of inter- about 1250 ft.
est. Doubling the length will double the cumulative risks, if all
other factors are constant.
One study [67] recommends that standardized lengths of VII. Risk criteria
pipeline, predetermined based on population density, be used in
risk calculations: 150 m for the highest population density and Establishment of risk criteria is the common method by which
100 m for suburban areas. Case Study C in Chapter I4 avoids risk acceptability is expressed. Setting and communicating risk
the use of terms such as individual risk and societal risk and criteria are obviously challenging and controversial (see risk
substitutes segment-specific risk and overall risk. The segment- communications, page 352). For example, documenting that, as
specific risk is based on 2500 ft, which is derived from calcula- a by-product of a certain activity, a certain number of fatalities