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ALARP: As Low as Reasonably Practicable Risk |
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Acronyms
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Due to the subjective nature of risk, no external agency, whether it be a regulatory body, a professional society or the author of a web page such as this can provide an objective value for ALARP. One large oil company, for example, has an internal ALARP guide that is over 30 pages long. Yet at no point in the document is any numerical guidance to do with acceptable risk provided. Nevertheless individuals and organizations are constantly gauging the level of risk that they face in their personal and work lives, and then acting on their assessment of that risk. For example, at a personal level, an individual has to make a judgment as to whether it is safe or not to cross a busy road. In industrial facilities managers make risk-based decisions regarding issues such as whether to shut down an equipment item for maintenance or to keep it running for another week. Other risk-based decisions made by managers are whether or not an operator needs additional training, whether to install an additional safety shower in a hazardous area, and whether a full Hazard and Operability Analysis (HAZOP) is needed to review a proposed change. Engineering standards and other professional documents can provide guidance. But, at the end of the day, the manager has a risk-based decision to make. That decision implies that some estimate of 'acceptable risk' has been made. As Low as Reasonably Practicable Risk - ALARPBoundaries of risk that are 'definitely acceptable' or 'definitely not acceptable' are established as shown in the Figure below, which is an FN curve family, as discussed in Chapter 1 of the book Process Risk and Reliability Management. Between those boundaries, a balance between risk and benefit must be established. If a facility proposes to take a high level of risk, then the resulting benefit must be very high.
One expert panel has developed the following guidance for determining the meaning of the term 'As Low as Reasonably Practical'.
Difficulties with ALARPThe fundamental difficulty with the concept of ALARP is that the term is inherently circular and self-referential. For example, the phrase 'best available technology' used in the list above can be defined as that level of technology which reduces risk to an acceptable level - in other words to the ALARP level. Clauses such as 'best operations' and 'high standard' face the same problem.Probably due to the difficulties in defining ALARP, the UK HSE, in the year 2006 started to minimize its emphasis to do with ALARP requirements from the Safety Case Regime for offshore facilities. Other major companies have also elected to move away from ALARP toward a continuous risk reduction model. De Minimis RiskThe notion of de minimis risk is similar to that of ALARP. A risk threshold is deemed to exist for all activities. Any activity whose risk falls below that threshold value can be ignored; no action needs to be taken to manage this de minimis risk. The term is borrowed from common law, where it is used in the expression of the doctrine de minimis non curat lex, or, 'the law does not concern itself with trifles'. In other words, there is no need to worry about low risk situations. Once more, however, an inherent circularity becomes apparent: for a risk to be de minimis it must be 'low', but no prescriptive guidance as to the meaning of the word 'low' is provided.Citations / Case LawCitations from regulatory agencies provide some measure for acceptable risk. For example, if an agency fines a company say $50,000 following a fatal accident, then it could be argued that the agency has set $50,000 as being the value of a human life. (Naturally, the agency's authority over what level of fines to set is constrained by many legal, political and precedent boundaries outside their control, so the above line of reasoning provides only limited guidance at best). Even if the magnitude of the penalties is ignored, an agency’s investigative and citation record serve to show which issues are of the greatest concern to it and to the community at large.Indexing MethodsSome companies and industries use indexing methods to evaluate acceptable risk. A facility receives positive and negative scores for design, environmental and operating factors. For example, a pipeline would receive positive points if it was in a remote location, or if the fluid inside the pipe was not toxic or flammable. Negative points are assigned if the pipeline was corroded or if the operators had not had sufficient training. The overall score is then compared to a target value (the acceptable risk level) in order to determine whether the operation, in its current mode, is safe or not.Although indexing systems are very useful, particularly for comparing alternatives, it has to be recognized that, as with ALARP, a fundamental circularity exists. Not only has an arbitrary value for the target value to be assigned, but the ranking system itself is built on judgment and experience, and so it is basically subjective. The biggest benefit of such systems, as with so many other risk-ranking exercises, is in comparing options. The focus is on relative risk, not on trying to determine absolute values for risk and for threshold values. |
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