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Safety and environmental standards for fuel storage sites
Final report
43
169 The phase of implementing good practice has raised a number of practical issues from the
field. This section of the PSLG Final Report provides further information on these aspects.
Bund lining systems
170 The COMAH Containment policy states that ‘Bunds shall be impermeable’ and that ‘bunds shall
have fire resistant structural integrity, joints and pipework penetrations’. This covers the preparation
of the tank base and foundation plus the selection of lining systems; concrete, earth or polymeric or
polymeric and mineral composites.
171 It is important that protection from fire is included in risk assessment for selecting different
types of lining systems.
172 The series of testing standards BS 476:
Fire tests on building materials and structures: Guide
to the principles and application of fire testing
33
provides a good guide.
173 There is no consolidated set of standards and guidance covering the options for lining
systems for existing tanks addressing both the issue of what to do under the tank and the
application of the selected system.
174 The selection of any system is based on a combination of risk (to the environment and
people), cost and practicality. Any consideration of improvements to lining systems for existing
establishments where the risk is tolerable should be subject to an ALARP assessment.
175 Table 2 provides examples of some commonly used lining systems. Advantages and
disadvantages may vary subject to site conditions. The list is indicative only and not exhaustive.
Fire resistance is covered in the table to reflect the current knowledge of performance based on
product information, performance in fire incidents and some testing that has been carried out by
Operators. Further testing is recommended on the relative performance of these lining systems
where information is lacking. This testing may also be used to optimise system designs.
Table 2
Lining system options
Option
Advantages
Disadvantages
Fire resistance Cost**
Concrete
Proven durability
––
Able to cast around
––
penetrations
Well suited to small
––
congested areas
Hydrocarbon resistance
––
Requires joints for
––
construction and
movement
Requires regular
––
maintenance of joint and
penetration sealants and
cracks
Can buckle under heat
––
Net excavation waste
––
can be high
Potential for settlement
––
and cracking
Very Good
––
Joints and
––
penetrations are
the weakness
High
Bentonite
(geosynthetic
clay liner)
(pre-hydrated
or dry bentonite
requiring in situ
hydration)
Hydrocarbon resistance
––
Lower maintenance
––
Self-sealing properties if
––
punctured.
Pre-hydrated can be
––
laid at performance
specification required
Requires a protection
––
layer.
Potential hidden
––
problems at penetrations.
Potential for drying out
––
on slopes
In situ hydration
––
of dry systems to
achieve performance
specification required
Can be uncertain
––
Good as
––
geotextile mat
protected by
layer of soil/
stone
Medium