How to Choose the Right Bunded Storage Unit for Your Site

Everything You Need to Know About Safe Hazardous Storage

Bunded storage is secondary containment. If a drum splits or a valve fails, the bund catches what comes out before it reaches your floor, your drains or the ground. That is the whole job, and it is why getting the specification right matters a good deal more than getting a keen price on the wrong unit.

Here is what to check before you buy.

What type of bunded storage unit do I need?

Start with volume and location, because those two answers narrow the field quickly.

• Bunded cabinets are the smallest option, usually for indoor use in a workshop or stores. They suit small containers, workshop chemicals and part-used drums.
• Bunded pallets and spill pallets sit underneath drums or IBCs where you need containment but not an enclosure.
• Walk-in bunded units and chemical stores handle higher volumes, are normally sited outdoors, and can be specified with internal shelving, racking and ventilation.

If the unit is going outdoors, you need robust weather protection and a plan for how it will be sited and secured. A fully loaded chemical store is not something you reposition on a whim.

Materials: check compatibility first

Some materials react badly with the substances you are storing, which turns a containment measure into a hazard of its own. Mild steel is fine for oils and fuels but the wrong choice for certain acids, where polyethylene or GRP is safer.

Check your safety data sheets against a chemical compatibility chart before you order. If you are storing more than one substance, check they are compatible with each other as well as with the unit — incompatible substances need segregating, not stacking.

Safety features to check

• Spill containment capacity. See the next section — this is the number that matters most.
• Ventilation. Without it, vapour accumulates inside the unit. With the wrong sort, it escapes somewhere you did not intend.
• Fire resistance. Relevant where you are storing flammable liquids. HSE guidance HSG51, The storage of flammable liquids in containers, sets out good practice for containers up to 1,000 litres and sits alongside your legal duties under DSEAR. Not every unit needs a fire rating, but if yours does, make sure the rating is stated and you know which standard it is measured against.
• Security. Lockable, and sited where unauthorised access is difficult. Theft of fuel and solvents is common, and so is casual interference.
• Access and layout. If a unit is awkward to load, people will leave containers standing outside it — which defeats the point entirely. Internal shelf heights, door width and whether you can get a drum trolley through all matter more than they sound like they should.

How big does the bund need to be?

For oil storage in England, the Control of Pollution (Oil Storage) (England) Regulations 2001 require the bund to hold at least 110% of the container’s capacity. Where there is more than one container, it must hold 110% of the largest, or 25% of their combined total, whichever is greater. Scotland, Wales and Northern Ireland have their own equivalent rules.

110% is the figure most reputable suppliers build to as standard, and it is the first thing to look for on a specification sheet. If a unit does not state its bund capacity, ask. If the supplier cannot tell you, that is your answer.

Compliance and practical requirements

Three separate regimes may apply, and they cover different risks. Knowing which is which saves a lot of confusion:

Then plan the practicalities. Decide how often you will inspect the unit and the bund, who is responsible for doing it, where the spill kit lives, and what happens to anything the bund catches. A bund with six inches of rainwater in it has no spare capacity for a spill.

Choosing a supplier

Buy from someone who will tell you the bund capacity, the material and what the unit is and is not rated for, without being asked twice. If a supplier cannot answer a compatibility question about the substance you are actually storing, that tells you something useful about the rest of the relationship.

Budget matters. But the cost of getting this wrong is a contaminated site and a conversation with the Environment Agency, not a slightly higher invoice.

Frequently asked questions

Does a bunded unit need to be fire rated?

Only where you are storing flammable liquids. HSG51 is the guidance to work from, and your DSEAR risk assessment should tell you what the substance and quantity actually require. A fire rating you do not need is money spent for nothing; one you do need and have not got is a different problem altogether.

How often should a bunded storage unit be inspected?

As a minimum, check that the bund is empty, clean and undamaged, and keep a written record of each check.

Can I store different chemicals in the same bunded unit?

Only if they are compatible with each other and with the material the unit is made from. Incompatible substances need segregating into separate units or separate bunded areas — your safety data sheets will tell you which.

What is the difference between a bunded cabinet and a bunded store?

Scale and location, mostly. A cabinet is a smaller indoor unit for workshop quantities. A walk-in store holds far more, usually lives outdoors, and can be fitted out internally with shelving and ventilation.

Talk to us today

Contact our team at Storage N Stuff and tell us what you are storing and how much of it. We will specify the right unit for the substance, the volume and the site.