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Safety and environmental standards for fuel storage sites
Final report
56
12 x 12
fire resistant sealer
(both sides)
Flexcell or similar approved
25ø fire retarding rope
Stainless steel waterstop
25
25
100
25
6000
(typical)
6000
(typical)
100 25
25
Notes: 1:
Fire retarding rope to be placed on both sides of an internal bund wall
All measurements in millimetres
2:
Waterstop, rope and fire resistant sealer to be omitted in bundwalls footings
3:
Stainless steel for waterbar to be grade 316 and 1.0 mm thick
Figure 12
Example puddle flange cast into a bund wall
Secondary containment systems under tanks
218 In addition to overfill events which are within PSLG scope, there have been a number of
significant leaks of gasoline, kerosene and diesel from the base of storage tanks.
219 It is important that secondary and tertiary containment systems are designed to deal with
both types of event.
220 The following provide additional guidance:
API 650
■
■
Welded tanks for oil storage
– Appendix I is the fundamental classic guide to prevent
bottom leakage from storage tanks.
API 340
■
■
Liquid release prevention and detection measures for aboveground storage tanks
.
38
API 341
■
■
A survey of diked-area liner use at aboveground storage tank facilities
.
39
EEMUA 183
■
■
Guide for the prevention of bottom leakage from vertical cylindrical steel storage
tanks
– Chapter 3 also provides similar data, but again quotes the API 650 and the repair
guide API 653.
BS EN 14015
■
■
Specification for the design and manufacture of site built vertical cylindrical flat-
bottomed above ground storage tanks
.
Basis for bund capacity based on tank capacity
221 Within the PSLG Final Report, particular emphasis is given to overfill prevention as this is the
primary means by which this major accident hazard can be prevented. In assessing what overfill
prevention measures are required to reduce the risk to the environment to ALARP, the existing
capacity of the bund and the tank level it was based on must be taken into account to determine
the potential environmental consequences, eg whether the spillage is likely to be retained by the
secondary containment system. If the overfill prevention system and the primary containment
measures as a whole are in accordance with good practice, the risk to the environment is reduced.
222 The COMAH Containment policy states that: ‘Bunds shall have sufficient capacity to allow for
tank failure and firewater management. This will normally be a minimum capacity of either 110%
of the capacity of the largest tank or 25% of the total capacity of all the tanks within the bund
whichever is the greater.’ It is unclear what is meant by ‘capacity’.