Bunding Best Practices

Bunding (secondary containment) is one of the simplest, most effective ways to reduce the risk of pollution, slips, fire hazards and costly clean-up when storing waste oil, fuels, coolants, cutting fluids or other liquids. A well-designed bund helps you contain leaks at source, keep spill response manageable, and demonstrate good environmental control during audits and inspections.

This page summarises practical best practice points you can apply on most sites, alongside UK guidance links for further reading.

1) Start with the basics: what “good” looks like

A bunded area should:

Contain foreseeable leaks and minor spills from the containers inside it.
Prevent escape to drains, soil and watercourses (including via cracks, pipe penetrations and open valves).
Remain usable in day-to-day operations (safe access, clear labelling, easy inspections).
Be supported by a simple, documented inspection and maintenance routine.

2) Capacity: design for realistic containment

As a rule of thumb, UK guidance commonly references bund/secondary containment capacity of 110% of the largest container and, where multiple containers share a bund, 25% of total stored volume (whichever is greater).¹² Always confirm what applies to your site (for example, by location, regulator, or specific substances stored).

Practical tip: Don’t forget displacement. Pallets, racking, tank feet and stored items reduce effective capacity. If you are close to the limit on paper, you may be under-capacity in real use.

3) Material selection and compatibility

Choose bund materials that resist the liquids stored and the environment they’re used in:

Concrete (often with a suitable chemical-resistant coating/liner) for long-term installations.
High-density polyethylene (HDPE) or other engineered polymers for many oils and fuels, especially for modular containment systems.
Steel bunds where appropriate, with protective coatings and corrosion control.

Compatibility matters: some chemicals, cleaning agents, and additives can degrade certain plastics and coatings over time. If you’re storing mixed fluids (for example oils plus degreasers), confirm material compatibility from manufacturer data and your COSHH assessments.

4) Keep it liquid-tight: base, walls, joints and penetrations

Many bund failures happen at weak points rather than the main wall. Best practice checks include:

Crack control and sealing (especially in concrete bases).
Bund wall-to-base joints sealed and protected from impact.
Pipework penetrations properly sealed (avoid unprotected holes through bund walls).
No open outlets that allow liquid to escape—bund drains should be locked/controlled and managed properly (see drainage section).

5) Drainage management: rainwater is not “free to drain”

Rainwater and wash-down water commonly accumulate in outdoor bunds. If you allow bunded water to build up, you lose capacity; if you drain it incorrectly, you risk pollution.

Best practice is to:

Use a controlled, lockable drainage point (not left open).
Check water for visible sheen/contamination before removal.
Dispose of contaminated liquids appropriately (often as waste), following site procedures and waste contractor guidance.
Where suitable, consider management systems such as oil/water separation arrangements—only where permitted and correctly maintained.

UK guidance on oil storage and secondary containment provides practical context on bund capacity and good control measures.¹²

6) Housekeeping: bunds should not become storage bays

Clutter reduces capacity, hides leaks, and slows response. Keep bunds tidy:

Store only what must be inside the bund (avoid unnecessary packaging, empty containers, loose absorbents, or general waste).
Keep access routes clear for handling and emergency response.
Use labelled storage positions to avoid “temporary” items becoming permanent.

7) Regular inspections and documented checks

Frequent inspections catch small issues before they become expensive incidents. A sensible routine typically includes:

Daily/weekly visual checks: leaks, staining, pooled liquids, blocked drains, impact damage.
Monthly recorded inspections: condition of walls/base, joints, penetrations, corrosion, signs of chemical attack.
After any incident: confirm bund integrity and capacity before returning to normal operation.

Document inspections for audit and compliance purposes. If you need an internal reference point, see: Regular inspections.

8) Training and awareness: make bunding “normal work”

Bunding only works if people use it correctly. Make sure all relevant staff understand:

Why bunding matters (environmental harm, legal duties, business disruption).
What to do if they see staining, leaks, or bunded water with an oil sheen.
How to isolate drains and deploy spill response equipment quickly.
Who to notify and how incidents are recorded.

9) Integrate bunding with spill response

Bunds reduce spread, but you still need response equipment sized for your risks. Practical considerations include:

Position spill kits near the risk (not buried in a store at the far end of site).
Match absorbents to the liquid (oil-selective for hydrocarbons, chemical absorbents where required).
Include drain protection where a release could reach surface water drains.

Related Serpro pages you may find useful: