Secondary Containment
Secondary containment is a practical, proven way to reduce the risk of pollution incidents when you store, decant, or handle liquids such as oils, fuels, coolants, chemicals, and trade liquids. In simple terms, it is a second “line of defence” designed to catch leaks, drips, overfills, and container failures before they can spread across floors, enter drains, or reach the environment.
Why secondary containment matters
A small, unmanaged leak can quickly become a safety issue (slips, fire risk, exposure) and an environmental incident if it reaches drainage or surface water. UK government guidance for businesses highlights the importance of preventing oil and chemical pollution and controlling where contaminated run-off can travel.[1]
Secondary containment helps you:
- Reduce clean-up time and cost by keeping spills in a controlled footprint
- Protect drains, interceptors, and outfalls from contamination
- Support compliance by demonstrating sensible prevention and control measures
- Improve housekeeping and reduce recurring drips in maintenance areas
Common secondary containment options
The “right” containment depends on your containers, site layout, and the liquids involved. Typical options include:
- Bunds (masonry, concrete, coated, or prefabricated) around tanks or storage areas
- Spill pallets and bunded pallets for drums and small containers
- IBC bunds and sump platforms for 1,000-litre IBCs
- Drip trays under pumps, valves, small containers, and frequent decant points
- Portable bunding and berms for temporary works, outdoor tasks, and maintenance shutdowns
- Drain protection as a rapid “protect the drain first” control during an incident
Useful related guidance and product guidance on Serpro includes:
Sizing and capacity basics
Capacity is a core principle of secondary containment. For oil storage, GOV.UK guidance sets out widely used rules of thumb, including 110% capacity for single containers, and for multiple containers the greater of 110% of the largest container or 25% of the combined capacity.[2] NetRegs also summarises the 110% / 25% approach for secondary containment systems (bunding).[3]
In practice, “usable capacity” matters as much as the headline number. You should consider displacement from:
- Container feet, frames, and pallet bases
- Pipework, pumps, and supports within the bund footprint
- Rainwater in outdoor installations (and how it will be managed)
For more detailed design considerations, see: Bund design guidelines.
Installation and layout tips that improve real-world performance
- Keep containment close to the risk: place trays/pallets directly under likely leak points and decanting locations
- Separate incompatible liquids: where substances should not mix, use separate containment and clear labelling
- Protect drainage routes: identify gullies and low spots; plan quick-deploy drain protection as part of your spill response
- Choose compatible materials: ensure the bund/tray material is suitable for the liquids stored (including temperature and exposure)
Inspection, maintenance, and records
Regular maintenance and inspection of secondary containment systems are vital to their effectiveness:
- Routine checks: Conduct regular inspections to ensure that the integrity of the containment system is intact and that there are no visible signs of damage.
- Cleanliness: Keep the containment area clean and free from debris that could obstruct drainage or containment functions.
- Documentation: Maintain records of inspections and maintenance activities to ensure compliance with regulations and to track any issues that arise.
For more detailed guidance on spill prevention and run-off control around chemical handling areas, refer to the GOV.UK guidance on pollution prevention for businesses.[1]
For further information on secondary containment systems, visit Serpro's secondary containment page.