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

The COMAH Safety Report Process for Predictive Assessment of Explosives Sites

Introduction

This document has been written to help operators who manufacture or store any explosives (including fireworks) in excess of the top-tier COMAH quantities, to fulfil their responsibilities for the risk analyses or "predictive" aspects as required in the preparation of safety reports by the COMAH Regulations. It is supplementary to other HSE published guidance and does not override the regulations or that guidance and does not introduce additional requirements. It offers an approach (not the only approach) which should help a duty holder to satisfy the Competent Authority (CA). The focus is specifically on sites which hold an explosives license under the Manufacture and Storage of Explosives Regulations 2005. Such sites have quantity-safety distances which generally ensures that the off-site risks from the explosion hazards are low. Where other substances such as toxics are present, they may present a significant off-site risk. On-site the explosives risks range from low (associated for example with explosives storage) through medium to high (with certain manufacturing operations). Therefore, risks associated with explosives substances at licensed sites are normally dominated by risks on-site.

When assessing safety reports, CA assessors use assessment criteria from the Safety Report Assessment Manual (SRAM) (available on the HSE web-site) to decide if the necessary demonstrations have been made. To satisfy the "predictive" criteria in the SRAM, operators must undertake a suitable and sufficient risk analysis to show that the risks from the installation and the operations undertaken on their sites have been reduced "as low as reasonably practicable" (ALARP). This guidance is intended to help operators to produce reports that will make the necessary demonstrations when the predictive assessment criteria are applied. The steps involved with this are as follows:-

identify all the major accident hazards (MAH’s) for the site and detail all the major accidents scenarios (MAS’s) [for an illustration of a MAS in the context of this guide see Step 1].
estimate the consequences and likelihood of each of the identified MAS’s.
select a representative set of MAS’s for detailed assessment (which must include the worst case scenario(s), see Step 3).
conduct a detailed assessment of each MAS in the representative set.
quantify the extent and severity of each MAS (i.e. how many people could be injured, hospitalised and killed).
demonstrate that for each MAS in the representative set, the risk is reduced ALARP. The depth of the demonstration will be driven by the magnitude of the hazards and risks presented by the site (known as proportionality).
demonstrate risks are ALARP for the other (non-representative set) MAS’s (see Step 5).

The steps in this process are summarised in the following flowchart (Figure 1) with each step then described in detail.

Figure 1 Flowchart showing Steps in Risk Analysis