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CDOIF
Chemical and Downstream Oil
Industries Forum
CDOIF is a collaborative venture formed to agree strategic areas for
joint industry / trade union / regulator action aimed at delivering
health, safety and environmental improvements with cross-sector
benefits.
6.2
Part 2 calculating the establishment risk frequencies
Part 1 of the risk assessment process has identified the ALARP band. Part 2 sets out
how to assess the risk from the establishment to the receptor:
x
Determine the risk from the establishment to a receptor
o
Determine the frequency of occurrence of all scenarios based on
available failure rate and/or event data (which may include
preventative or mitigatory layers and if so these should be clearly
identified in the assessments).
o
Total the frequency of all scenarios from the establishment that result
in each Consequence level (A-D) to the receptor.
o
The total frequency of events which meet or exceed each
consequence level of harm should then be compared with the
tolerability thresholds established in Part 1 (section 6.1). When
comparing the establishment frequency of lower consequence levels
(e.g. B) with the assigned ALARP bands, note that the total frequency
to be considered is the total of that and higher consequence levels
(i.e. B + C + D). An example of how aggregation is completed can be
found in section 6.2.1.
x
If the risk is still not Tolerable if ALARP (TifALARP) then assess other potential
control measures, accept/dismiss these within an ALARP demonstration and
integrate into site improvement plan as appropriate
6.2.1
Aggregating risk - Examples
Completing the initial screening (as described in section 6.1) will have discounted
potential receptors from the risk assessment process as the screening will have
determined that a MATTE is not credible.
For those substances and scenarios which do have MATTE potential, their risks to the
relevant receptor must now be determined. As it is the total risk to the receptor that is
required, i.e. from all substances, and credible scenarios, these risks must be
aggregated. Examples of how this can be achieved for each receptor are provided in the
following sections.
o
6.2.1.1 – Single substance stored in a single tank
o
6.2.1.2 – Tank farm or group of tanks containing similar substances
o
6.2.1.3 – Groups (e.g. tank farms) with dissimilar substances/incident
consequences
Guideline – Environmental Risk Tolerability for COMAH Establishments v1.0
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