Secondary Containment — Definition and Common Types

Secondary Containment — Definition and Common Types

What secondary containment is

Secondary containment refers to a passive or active barrier system placed around primary storage or process equipment to catch, hold, and control released liquids or solids that might escape from tanks, drums, piping, or other containers. The goal of secondary containment is to prevent migration of hazardous or polluting materials off-site or into storm drains, soil, or groundwater while responders take action.

Why secondary containment matters

Secondary containment reduces environmental risk, protects worker safety, and limits regulatory liability. A properly sized and maintained secondary containment system mitigates the consequences of failures such as overfills, corrosion-induced leaks, vehicle impact, or accidental discharge during transfer operations. For warehouses, manufacturing sites, fuel depots, and chemical plants, secondary containment is a fundamental element of an effective pollution prevention and emergency response strategy.

Common types of secondary containment

Secondary containment systems are selected based on the stored material, volumes, operational constraints, and applicable regulations.

Typical options include:

• Bunds and diked areas — Earthen, concrete, or steel walls surrounding storage tanks or tank groups that form an enclosed basin. Bunds are widely used for aboveground tanks and can be either permanent (concrete-lined) or temporary (portable barriers).

• Double-walled tanks and piping — A primary vessel contained within a secondary shell that provides space for leak detection and containment, common for high-risk liquids such as fuels and solvents.

• Containment pallets and sumps — Palletized units and recessed sump areas used for individual drums, IBCs (intermediate bulk containers), or small equipment to capture drips and small spills.

• Lined trenches and impermeable liners — Synthetic liners (HDPE, PVC) or concrete with protective coatings used to keep liquids from infiltrating soil, often paired with slope designs to an accessible collection point.

• Spill berms and portable dikes — Deployable barriers for temporary operations or emergency containment when a fixed system is impractical.

• Catch basins and retention ponds — Larger-scale containment for runoff or transfer operations, often combined with treatment systems or controlled discharge options.

Key design principles

Design of secondary containment should follow several basic principles: compatibility (materials must resist degradation by stored substances), capacity (sufficient volume to hold anticipated releases plus margin), impermeability (to protect soil and groundwater), and accessibility (for inspection, maintenance, and recovery). Typical sizing rules used by many facilities and guidance documents include designing to contain at least the volume of the largest single container plus freeboard, or a specified percentage of total on-site inventory — however, regulatory thresholds and formulas vary by jurisdiction, so confirm local requirements.

Detection and drainage

Containment basins are often equipped with leak detection alarms, sight glasses, or monitoring wells so releases are identified quickly. Drainage design must avoid accidental releases: drains should be manually controlled or routed to a holding tank rather than open to sewer or storm drains. Some designs include sumps with pumps and automatic isolation valves to allow recovery while preventing unauthorized discharge.

Materials and chemical compatibility

Selection of construction materials influences longevity and effectiveness. Concrete with protective coatings, reinforced HDPE liners, stainless steel, and specially formulated coatings are commonly used. Compatibility tables and chemical resistance charts should guide the choice of lining and containment pallet materials for acids, bases, solvents, fuels, and specialty chemicals.

Examples from practice

In a distribution warehouse storing drums of concentrated cleaning chemicals, secondary containment frequently takes the form of containment pallets sized for individual drums and a concrete bermed area beneath shelving storing multiple containers. At bulk fuel depots, double-walled tanks with leak detection and perimeter bunds are common. In a small manufacturer using solvent baths, a lined trench with a pump-back system and manual isolation valves allows controlled recovery of accidental discharges.

Regulatory and operational notes

Many permitting programs and environmental regulations require secondary containment for certain classes of materials. Operators should document their design rationale, perform periodic inspections, maintain records of repairs and tests, and integrate containment into emergency response plans. Secondary containment is not a substitute for good operational controls—proper handling, training, and maintenance remain essential.

Summary

Secondary containment is a practical, proven layer of protection that minimizes the impact of spills and leaks. By matching the type of containment to the chemical hazards, expected volumes, and site operations, facilities can protect health, the environment, and business continuity while meeting regulatory expectations.