Safety Risk Assessment for High Hazard Industries: To Quantify or Not To Quantify?

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1 Safety Risk Assessment for High Hazard Industries: To Quantify or Not To Quantify?

2 About ARCADIS ARCADIS was established in the Netherlands more than a century ago Our global reach extends across Europe, North and South America, the middle East and Asia IMAGE With over 21,000 staff, we rank in the top 10 management and engineering companies Our extensive network enables us to share information, innovation and market trends to the benefit of all our clients worldwide ARCADIS has a specialist team dealing with safety and systems assurance, applying risk assessment techniques across a range of industries. Staff within the ARCADIS team also have experience in project risk management, commercial risk and operational risk. 2 of May ARCADIS Newtown Creek waste water treatment facility, New York NY

3 Definition of Safety Risk A hazard is a situation with the potential to cause harm Risk of hazard = likelihood (probability, frequency) x consequence (severity) Model Development Prior to a risk assessment we create a model (of the situation, system, operation, etc., as appropriate) Determine the boundaries and scope. Focus on the Safety Functions Consider physical or functional interfaces, and the surrounding environment/geography/local ambient conditions. Consider whether to do a full QRA, partial QRA, or none at all. Must demonstrate that risk is tolerably low

4 Accuracy of Model vs. Precision of Results to Support Decision Making

5 Deciding When to Quantify Is data available for the model? Is it any good? What are the [perceived] high consequence/risk events? Has the client asked for QRA? Is it merited? Is client aware of alternatives? Is there a regulatory and/or industry expectation/ requirement? Are there quantitative targets to meet? What are the safety objectives how will these be met? Where are we in the project lifecycle? Is there a time restriction or cost factor?

6 Types of Quantitative Risk Assessment Full QRAs involve a probabilistic approach and uses mathematical techniques Partial QRAs will typically involve a Risk Class Matrix approach Qualitative Assessment of Risks (QAR) may also use a matrix approach as above, but without numerical bands.

7 Options Target No QRA No Target No QRA - Yes Target Yes QRA - No Target Yes QRA - Yes

8 Target - No QRA No There is no quantitative target and we don t need to know the numerical safety risk for any other reason Carry out a purely qualitative risk assessment Example: Passenger Emergency Alarm Covers Before Risk Assessment Following Risk Assessment

9 Target - No QRA -Yes There is no quantitative target but for some reason we need to know the numerical risk For example, comparison of risks of different types (normalising risks in differing categories) Carry out full or partial QRA

10 Target - Yes QRA No (or Partial) There is a quantitative target, but data is sparse or of poor quality In absence of good data, consider whether quantification is beneficial Can a robust qualitative assessment be made? Rely on engineering judgement, DID, argumentation, other techniques, to conclude that a quantitative target can be met.

11 Target - Yes QRA - Yes There is a quantitative target generally driven by known or perceived high hazards In the nuclear industry, numerical risk targets include BSOs and BSLs associated with annual risk of death to workers and the general public Similar targets in other industries, e.g. Rail Air Oil & Gas Process/chemical Good quality data generally available Full or partial QRA?

12 Both QRA and QAR support decision-making processes. Take-Away Messages QAR can be used at any time in the project lifecycle. The application of QRA is more limited, but usually highly focussed Even when there are targets, you may not always do a full QRA When there are no targets, you may still decide to do QRA. Accuracy of model more important than the precision of the numerical risk data output from it In an ideal world, all hazards would be eliminated by design therefore QRA wouldn t be needed. However, this doesn t happen in real life.

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