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Safety and environmental standards for fuel storage sites
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19 This guidance supports both simple and more complex applications of LOPA to assess the
risks arising from a storage tank overflow. The simpler applications are associated with greater
conservatism and less onerous requirements for providing supporting justification. The more
complex applications will often require greater amounts of supporting justification and may
require specialist input from experts in human factors analysis, risk quantification, dispersion and
consequence modelling. Also, as the analysis becomes more complex, it may prove harder to
provide long-term assurance that the assumptions in the assessment will remain valid. Users of
this guidance should therefore not only consider what factors are currently relevant, but also what
is required to make sure that they continue to be relevant.
20 Although this guidance focuses on the LOPA technique, other techniques such as fault tree
analysis or detailed quantitative risk assessment, used separately, may be a more appropriate
alternative under some circumstances. Quantified methods can also be used in support of data
used in a LOPA study. It is common practice with many dutyholders to use detailed quantified risk
assessment where multiple outcomes need to be evaluated to characterise the risk sufficiently,
where there may be serious off-site consequences, where the Societal Risk of the site is to be
evaluated, or where high levels of risk reduction are required.
21 As the LOPA study proceeds, the team should consider whether the complexity of the
analysis is still appropriate or manageable within a LOPA or whether a more detailed technique
should be used independently of the LOPA technique. Where a more detailed analysis is
undertaken, much of this guidance will still be applicable. In all cases the analyst is responsible
for ensuring that the appropriate level of substantiation is provided for the complexity of the study
being undertaken.
22 To simplify the use of this guidance, a flow chart mapping out the overall process is included
(Figure 22).