What is a bunded tank and do I need one for my diesel generator?

Date: 17/10/24

When purchasing or hiring a diesel generator, you'll require a bulk fuel tank to safely store the diesel that powers it. In most cases, it's now a legal requirement for these tanks to be bunded.

This requirement was introduced because bunded tanks offer more environmental protection than single-skin tanks (those without a bund) and are the safest way to store fuel. In this article, UK Sales Manager Russell Pritchard explains what bunded tanks are, why they are needed, and how to ensure you comply with relevant regulations when using a diesel generator.

Please note: The regulations we focus on here apply to commercial storage in England and Wales. While advice across all areas of the UK is broadly similar, there are important aspects that differ.

What is a bunded tank?

A bunded tank has an "outer bund," meaning it has two "skins" – essentially, it's a tank within a tank. The diesel is held in the inner tank (or skin), and the outer skin provides secondary containment and protection. 

Bunded tanks offer added protection against contamination and leakages, making them the safest way to store fuel. If the inner skin cracks, the bund will retain the fuel, preventing environmental damage to the surrounding area.

Do I need a bunded tank?

Anyone storing fuels is required to do so in a safe, responsible, and environmentally friendly way. However, the exact requirements differ depending on where and how your generator will be used.

If you are storing diesel in a container with a capacity of 200 litres or more on commercial premises, you must follow the oil storage regulations for businesses – the Control of Pollution (Oil Storage) (England) Regulations 2001, known as COPSR. Properties used for business purposes and public sector buildings, such as schools, hospitals, and leisure centres, are all classified as commercial premises under the regulation.

The primary intention of COPSR is to protect the oil from the environment and the environment from the oil. While it doesn't set any limits on how much diesel you can store, it contains several key rules on how you store it.

What does this mean for stand-by generators kept for emergency use?

The official wording in COPSR can be technical, but essentially, a bulk fuel tank for a stand-by generator used in a commercial setting needs to:

• Be installed in the right place to avoid damage while allowing for safe filling and maintenance access.

• Be strong enough to withstand ordinary use.

• Have a secondary containment feature to reduce the risk of oil leaking into the environment.

This secondary containment can either be a drip tray or a bund. However, in practice, a bund is a simpler solution, especially for larger storage tanks.

A bund, meanwhile, can either be ‘integrally bunded’, where the outer shell of a tank manufactured as part of the tank system, or an external bund – a structure made from masonry or concrete within which the container is stored.

For obvious reasons, an integrally bunded tank is preferable in almost all installations.

Bund requirements

The bund must meet ISO 9001 and DSEAR Regulation 6(4)(e) requirements, meaning that it:

• Can hold 110% of the tank's capacity.

• Is impermeable to oil and water.

• Has a lifespan of 20 years with maintenance.

• Does not have any pipe, valve, or other opening in the base or walls that would allow it to be drained.

• Contains every part of the oil storage container and associated equipment, such as valves.

Any business that stores more than 200 litres of diesel is also required to obtain an oil storage certificate from their local council, to demonstrate compliance with all necessary requirements.

What happens if I don't follow the rules?

If you do not follow the relevant requirements for storing oil, you could be fined or prosecuted. 

The Environment Agency can also serve an anti-pollution works notice if your storage container isn't up to legal standards, forcing you to bring it up to code or even replace it to avoid legal action.

If you're unsure if you are meeting the requirements of the regulations, you can always contact the Environment Agency for advice.

However, when you work with a specialist like Central Power Services, the stress is taken away. We develop and provide bespoke compliant diesel storage solutions for all our customers, alongside fuel management services that ensure the tanks are always topped up and provide maximum reliability.

If you want to find out more about how we can help you, get in touch on 0845 437 9750.

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