Operators of COMAH or ‘Seveso’ establishments are required to demonstrate that all necessary measures are in place at their establishments to prevent major accidents occurring and to limit the consequences of any such major accidents for human health and the environment.
A key element in the process to demonstrate compliance with this obligation is the undertaking of a comprehensive assessment of the risks of a major accident at the site. The assessment must demonstrate that the residual risks (i.e. after taking account of the risk reduction and mitigation measures in place) are reasonable in the context of the technical potential for additional risk reduction measures, and the cost of such measures.
If this cannot be demonstrated, operators may need to invest in potentially costly additional measures to further reduce the level of residual risk.
Limitations of traditional approaches
While traditional matrix-based hazard identification and risk assessment (HAZID&RA) techniques are useful for identifying the scenarios that present the greatest risks, they are often insufficient for fully determining the cost-benefit trade-offs associated with additional risk reduction measures. In such circumstances, other techniques are required to demonstrate compliance and inform investment decision-making.
Layers of protection analysis (LOPA) is a technique that was originally developed for the process industry to assess the adequacy of the protective measures in place for an activity. LOPA is typically used to undertake more detailed analysis of accident scenarios that have already been assessed using other higher-level techniques (e.g. HAZID&RA or Hazop) - on the basis of consequences (credible worst case scenarios) or risk.
When LOPA is undertaken for the purposes of COMAH / Seveso compliance, the focus is on the risks of major accidents to human health and/or the environment. It can be a powerful approach for evaluating scenarios that have well-defined initiating events, that incorporate well-defined independent protective layers (consistent with the LOPA framework of effectiveness, independence and auditability) and that rely on those protective layers as the scenarios evolve.
Is additional investment required?
The risk associated with each scenario can be evaluated and compared with established criteria. A demonstration that all necessary measures are in place typically comprises two elements of analysis: a determination of the overall level of risk from the establishment and an assessment of whether investment in further risk reduction measures is justified. LOPA can play an important role in both:
- LOPA can be used to estimate the overall risk from an establishment based on an analysis of the scenarios contributing to that risk. It is often used in conjunction with other complementary techniques for this purpose.
- In appropriate circumstances, LOPA can also be used to analyse particular scenarios of interest and quantify the level of individual or societal risk posed. Importantly, LOPA can also determine the impact on risk of additional risk reduction measures. In conjunction with cost-benefit analysis, LOPA results can be used to demonstrate whether all necessary measures are in place.
In this way, LOPA can be an important tool for informing investment decisions. It can enable operators to make the right investments in 'necessary measures'. LOPA can also provide evidence in support of existing measures, enabling operators to forego investment in unnecessary infrastructure, thereby allowing capital to be allocated more productively.