Risk analyses or ‘predictive’ aspects of comah safety reports guidance for explosives sites

The COMAH Safety Report Process for Predictive Assessment of Explosives Sites

Step 5: Demonstration of ALARP for the Representative Set

For all MA’s, the starting point will be to demonstrate that relevant good practice is in place, or if not, to justify why not. Thereafter, having characterised the risk associated with each of the MAS’s, it will be necessary to provide clear demonstrations that they are not unacceptable…….

Note: on HSE’s Tolerability of Risk (TOR) framework, the risks arising to workers and members of the public from the operations undertaken on site can fall in one of three regions; ‘broadly acceptable’, ‘tolerable’ if ALARP and ‘unacceptable’ as set out in the HSE publication Reducing Risks, Protecting People framework, below.

…. and have been reduced as low as is reasonably practicable (ALARP).

Note: An individual risk of death of less than 10-6 per annum is regarded as "broadly acceptable". Individual risks above this threshold are acceptable only if all necessary measures have been taken to achieve a level as low as reasonably practicable. Further guidance can be found in HSE’s/HID’s Semi Permanent Circular SPC/Permissioning/12 ‘Guidance on ALARP Decisions in COMAH’.

In simple terms this ALARP demonstration should identify both ‘what more could be done (i.e. what additional measures could be put in place) and ‘why these are not necessary ’. This exercise will:-

• require information on which processes are operated remotely, and on the philosophy regarding remote versus non-remote manufacturing.
• require information on what corresponding controls are in place, including the relevant good practice as found in ACoP’s, HSE guidance, recognised standards, industry practice, which indicate the minimum compliance standard.
• for the "tolerable if ALARP" region, require a detailed consideration of control measures and a rigorous demonstration that all measures necessary have been taken to reduce the residual risk ALARP. When no further reasonably practicable risk reduction measures can be identified then the residual risks are ALARP.
• for the broadly acceptable region, require a demonstration based on the adoption of relevant good practice, engineering standards, recognised codes and guidance. Obvious and reasonably practicable risk reduction measures should be introduced.

The ALARP demonstration described in the safety report should:

• show the link to initiators, the engineered and procedural safeguards in place and possible additional measures to prevent, control or mitigate the events.
• be presented on a scenario basis, with a list of further measures to prevent or minimise / mitigate the effects of the event and associated justification as to why the measures are not necessary. It should be noted that it need not necessarily be quantitative, the degree of rigour depends on the scale of the hazards and risks. Where a measure provides benefits for several scenarios the collective benefits will need to be considered.
• consider tolerability. This could involve using a risk matrix that has been broadly calibrated against HSE’s risk criteria.
• as well as individual risk, consideration can be given to multiple-fatality or group risk. The criteria derived from the HSE document ‘SPC/Permissioning/09 – HID’s Approach to ALARP Decisions’, available from the HSE’s web site may be appropriate.
• show that the costs (that is, the "sacrifice", whether in money, time or trouble) in providing any further measures are ‘grossly disproportionate’ to the benefit. When further measures can only be implemented at costs which outweigh the benefits by a factor which is grossly disproportionate, the risks can be said to be controlled ALARP.
• a "cost-benefit" analysis (not necessarily quantified) can be a useful method for assessing measures to inform judgements made on reduction of risks ALARP.
• the use of fault trees can form the basis of an acceptable ALARP demonstration, in that it displays clear links between further measures and how they influence the event sequence. However, this approach represents a significant resource requirement and care is needed to ensure that the higher risk operations are considered – prioritisation using a risk matrix is often proportionate.

It is sometimes impractical for new Duty Holders to perform case specific demonstrations for all identified events immediately. A more pragmatic option in such cases is for the "representative set " of MAS’s to be considered immediately, with the remaining risk generators being subject to scrutiny in a rolling program, leading up to the time of the next safety report submission. For such cases, the safety report should explain and justify the basis of action taken and provide justifiable plans for completion of additional assessments within a reasonable timeframe (not later than 5 years). If the additional assessments lead to material changes to the safety report and the demonstration of ALARP, a revision report may be required before the next 5 yearly submission.