Bund
Bunds provide a ‘second line of defence’ for controlling hazards events. They are a form of enclosure that surrounds drums or tanks, providing emergency containment in the event of a failure. Bunds can help to stop hazardous materials such as flammable or toxic liquids leaking onto the ground or into surface water, protecting the environment from chemical spills.
Typically, bunds are constructed using concrete or masonry, which may be reinforced and lined depending on the volume and nature of the material being stored. They wrap around single tanks or a group of tanks and provide secondary containment should the primary containment fail.
In many countries bunds are a legal requirement for the storage of certain materials. In the UK, it is best practise to bund hazardous materials unless a risk assessment shows that this is not necessary.
Generally, bund capacity should be 110% of the largest tank or 25% of the total tank capacity, whichever is the greater. Space can be limited on many sites, so a small footprint can be desirable. The higher the bund walls the smaller the area required for the same bund capacity. However, there are limits as to how high the bund walls can be in order that they do not prevent firefighting or more general access and to allow natural ventilation. As a consequence, they are typically 1 to 1.5 metres high. However, in some circumstances they may be as high as the tanks themselves.
Ideally, the bund should be protected from rain accumulation, if not rainwater will need to be removed at regular intervals, to ensure the bund has sufficient remaining capacity in the event of a tank failure. This can be achieved by a valved drain that is opened to remove accumulated water. However, regimes must be in place to ensure that the valve is generally closed, and to prevent drain blockage.
It is normal to limit the number of tanks in a single bund to 60,000 m3 total capacity. Incompatible materials should have separate bunds.
Bunds should be hydrostatically tested after construction is completed, before tanks are positioned within the bund walls. It is important that bunds are tested regularly after being constructed to ensure they continue to provide the protection that is required.
Alternatives to bunds include earth dikes, sumps and interceptors.
In addition, bunded tanks are available that include a second skin protecting agianst leakage and meaning a separate bund wall may not be necessary.
NB The SuDS Manual published by CIRIA in 2015 defines a bund as: ‘A barrier, dam or mound usually formed from earthworks material and used to contain or exclude water (or other liquids) in/from an area of the site.’
Containment systems for the prevention of pollution, Secondary, tertiary and other measures for industrial and commercial premises (CIRIA C736), published by CIRIA in 2014, defines a bund as: ‘A facility (including walls and a base) built around an area where potentially polluting materials are handled, processed or stored. This is for the purposes of containing any unintended escape of material from that area until such time as remedial action can be taken. Bunds are usually structurally independent from the primary containment tank.’
See also: Banding for an alternative definition.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
The CIAT principal designer register
Providing assurance and verification of the capability and competence of registered ATs.
Building Safety recommendations and Northern Ireland
The NI roadmap to improving safety in high rise residential.
BSA residential sector competence standards guidance
BSAS 01:2024 Organisational Capability Management System Standard - Competence Assurance.
Specifying rendered external wall insulation for fire safety
How to interrogate the evidence provided to the specifier.
The benefits of writing articles for your organisation
How to create a profile for your organisation and publish for free.
No Falls Week. The importance of safe working at height
What to expect and what is on offer to avoid accidents.
Scottish Government action to reach net-zero targets
Retrofit expert group highlight critical actions needed.
A forward thinking, inclusive global community of members.
From engineered product life-spans, to their extension.
Circular economy in the built environment
A brief description from 2021. Where are we now?
CLC publishes domestic retrofit competency framework
Roadmap of Skills for net zero.
Understanding is key to conservation.
Open industry engagement survey seeks responses
Institutions and the importance of engagement.
National Retrofit Hub unveils new guide
Digital Building Logbooks and Retrofit: An Introduction.