Secondary containment — commonly referred to as bunding — is one of the most critical components of a compliant liquid chemical or fuel storage system. When a primary container fails or a spill occurs, a correctly specified bund is the last line of defence before hazardous substances reach drains, groundwater, or the surrounding environment. The question facing many site managers is not whether to bund, but which type of bunding best suits their operational needs.
The Legal Requirement for Bunding
UK legislation mandates secondary containment for a wide range of liquid storage scenarios:
- Water Resources Act 1991 — prevents pollutants entering controlled waters; bunding is a key compliance measure
- Control of Pollution (Oil Storage) (England) Regulations 2001 — requires bunding for above-ground oil storage containers above 200 litres
- COMAH Regulations 2015 (Control of Major Accident Hazards) — applies to sites storing large quantities of dangerous substances
- COSHH Regulations 2002 — spill containment as a control measure for hazardous substances
- Environmental Permitting (England and Wales) Regulations 2016 — permit conditions commonly require secondary containment
The Environment Agency's guidance on oil storage states that bunds must hold at least 110% of the largest container's capacity, or 25% of the total storage volume (whichever is greater). This 110% rule is widely adopted as best practice for all liquid containment scenarios, not just oil.
Permanent Bunds: When They Work Best
A permanent bund is a fixed structure — typically constructed from concrete, masonry, or steel — integrated into the fabric of a building or hardstanding area. These are most appropriate for:
- Fixed bulk storage tanks (fuel, chemicals, IBC farms)
- Large-volume storage that is unlikely to be relocated
- Sites with planning consent and capital budget for civil works
- High-risk or COMAH-regulated sites where robustness and longevity are paramount
Advantages of permanent bunds include structural integrity, high capacity, resistance to impact, and longevity. However, they require civil engineering work, are inflexible once built, and cannot be adapted quickly if storage requirements change.
Portable Bunds: Flexibility Without Compromise
Portable bunding — also called folding bunds, flexible bunds, or spill pallets — offers a practical alternative or complement to permanent bunding. Modern portable bunds are manufactured from high-density polyethylene (HDPE), steel, or coated geotextile materials and can accommodate single or multiple containers without the need for civil works.
| Feature | Portable Bund | Permanent Bund |
|---|---|---|
| Installation | No civil works required | Requires civil engineering |
| Relocation | Easy — deploy anywhere | Fixed once built |
| Capacity | Typically up to 4,000L (larger folding bunds available) | Effectively unlimited |
| Cost | Lower upfront cost | Higher capital expenditure |
| Maintenance | Regular inspection, cleaning | Periodic structural inspection |
| Chemical resistance | Select grade to match substance | Concrete may require lining for acids |
| Emergency use | Ideal for temporary or incident use | Not practical for emergency deployment |
Types of Portable Bund
The portable bunding market offers several distinct product types to meet different scenarios:
- Spill pallets — rigid HDPE or steel platforms with integral sump; ideal for drums, IBCs, and small tank storage; compliant with 110% rule for single containers
- Folding fabric bunds — geotextile walls on a frame; deploy rapidly around existing storage; available in large formats for vehicle or plant decontamination areas
- Drive-over bunds — low-profile with ramps; allow forklift access while maintaining containment; suitable for IBC and drum storage in busy warehouses
- Emergency spill bunds — lightweight, deployable within seconds; used during deliveries, transfers, or spill incidents to rapidly contain liquids
- Chemical-resistant bunds — specialist materials (e.g., HDPE, stainless steel) for aggressive acids, alkalis, or solvents
Choosing the Right Solution for Your Site
The right choice depends on your specific hazard profile, volume of storage, operational flexibility, and site constraints. As a starting point, ask:
- Is this storage permanent, or might it move? (Portable if flexible)
- What is the total volume to be contained? (Confirm 110% compliance)
- What substances are stored? (Verify chemical compatibility)
- Do vehicles need access to the bunded area? (Consider drive-over options)
- Is an emergency deployment capability needed? (Emergency bunds or drain covers)
At Spill Control Products UK — Bunding and Secondary Containment, we supply a comprehensive range of portable bunds, spill pallets, and folding bunds to suit all scenarios. Our team can help you select the correct capacity and specification for your storage arrangement, ensuring full compliance with the 110% rule and Environment Agency guidance.
Pair your bunding with drain protection equipment and spill kits for a fully integrated secondary containment strategy.
Need expert advice? Call 01744 520 110