Secondary Containment — Design, Regulations, and Types

Secondary containment is a protective system that captures leaks and spills from primary storage to prevent environmental release and workplace hazards. It includes bunds, dikes, double-walled tanks, spill pallets, and similar measures.

Secondary Containment — Design, Regulations, and Types

Secondary Containment refers to engineered measures placed around primary storage or process equipment to capture/releases of hazardous or polluting liquids, preventing them from reaching the environment, drains, or areas where they could create safety or regulatory problems.

The purpose is straightforward and practical: if the primary container fails, the secondary system contains the product so it can be recovered, treated, or disposed of safely.

Design and implementation of a secondary containment system start with a clear risk assessment. Consider what substances are stored, the maximum single container size, anticipated release scenarios, proximity to storm drains or sensitive receptors, and local regulations.

Secondary containment systems vary widely by application and material, and common types include:

• Bunded Areas and Dikes — Continuous walls or curbs around tanks, drums, or chemical storage areas that form an enclosed reservoir.

• Spill Pallets and Trays — Portable containment for drums and small containers, often polyethylene or steel with sump capacity sized to hold worst-case spills.

• Double-walled Tanks and Piping — Tanks or piping systems constructed with an inner primary wall and outer secondary wall, with leak detection between them.

• Containment Sumps and Curbed Floors — Recessed or sloped floors that direct liquids to a sump for recovery or controlled treatment.

• Temporary Berms and Portable Bunds — Modular or inflatable containment used for temporary storage or emergency response.

Key design considerations

Compatibility of containment materials with stored liquids, structural integrity, capacity, freeboard, and access for inspection and cleanup. Effective secondary containment usually provides the capacity to capture the largest foreseeable release plus a safety margin. Industry practice often requires capacity sufficient for the largest single container plus additional allowance to account for precipitation or sloshing when outdoor storage is involved.

Regulatory drivers differ by jurisdiction and by the type of material stored. For example, oil storage often falls under specific rules that mandate secondary containment and written spill prevention plans, while hazardous chemicals can be covered by workplace safety and environmental regulations.

Designers should consult national and local regulations, such as oil spill prevention programs, hazardous waste rules, and stormwater requirements, and align designs with recognized standards and guidance from agencies and industry bodies.

Construction materials

Concrete, coated steel, high-density polyethylene, and chemically resistant liners. Each material has tradeoffs: concrete is durable and common in fixed bunds, but needs appropriate coatings and joints to resist chemical attack; polyethylene is corrosion-resistant and low-maintenance but can be vulnerable to UV and mechanical damage. Drainage within bunds should be controlled: drains used for removal must be lockable or have valves and be connected to recovery systems to prevent accidental discharge to sewers or storm drains. Inspection and maintenance are essential.

Typical practices

Routine visual inspections for cracks, corrosion, or accumulated liquids, functional checks of valves and leak detection systems, periodic integrity testing, and immediate remediation of defects. Recordkeeping of inspections, repairs, and training helps demonstrate due diligence and can support compliance during audits.

Operational integration is also important. Good secondary containment is complemented by spill response plans, trained personnel, spill kits positioned where needed, clear signage, and safe procedures for transferring liquids to minimize overfills and accidental releases. Engineering controls alone are not sufficient unless accompanied by robust operating practices.

Common mistakes

Underestimating containment capacity, using incompatible materials, allowing unsecured drains, neglecting maintenance, and failing to consider stormwater when containment is outdoors. Practical examples include a manufacturing plant that retrofit its drum storage area with spill pallets and absorbents to eliminate floor drains that previously allowed accidental discharges to municipal sewers, and a fuel depot that installed double-walled tanks with interstitial monitoring to detect leaks early.

In Summary

Effective secondary containment is a combination of sound engineering, regulatory awareness, and disciplined operations. When done well it protects people, compliance status, assets, and the environment, while reducing the costs and reputational risks associated with spills.