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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.
Scenario
(Tank Farm T1)
Consequence
Level
1
Event
frequency
1
Independent
mitigation
layers (PFD)
1
Outcome
frequency
(mitigated)
Catastrophic tank
failure
B
F1, 1x10
-6
0.1 * 0.1
F5, 1x10
-8
Large hole
A
F2, 1x10
-5
0.1 * 0.1
F6, 1x10
-7
Small leak from
tank base
A
F3, 1x10
-4
0.1 * 0.1
F7, 1x10
-6
Scenario
(Warehouse)
Consequence
Level
1
Event
frequency
1
Independent
mitigation
layer (PFD)
1
Outcome
frequency
(mitigated)
Warehouse fire
B
F4, 1x10
-3
0.1
F8, 1x10
-4
Note 1: Provided for illustrative purposes only. For event frequencies refer to section
4.3.4 ‘Determining risk frequencies’. For consequence level, refer to ‘MATTE
thresholds’, section 3.2.
The aggregated mitigated risk to the receptor for all credible scenarios can be calculated
as follows:
Category B mitigated frequency = F5 + F8 = 1x10
-8
+ 1x10
-4
= 1.0001x10
-4
Category A mitigated frequency = Category A frequencies + Category B frequencies
= (F6 + F7) + (F5 + F8)
= 1x10
-7
+ 1x10
-6
+ 1x10
-8
+ 1x10
-4
= 1.0111x10
-4
Guideline – Environmental Risk Tolerability for COMAH Establishments v1.0
Page 40 of 88