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• January 22, 2019

Secondary Containment for Industrial Tanks: Requirements & Guide

Industrial storage tanks hold chemicals, oils, wastewater, fuels, and other liquids used in manufacturing and processing operations. Although a properly designed primary tank provides the main barrier against leaks, facilities may also need a secondary containment system.

Secondary containment provides an additional barrier around a storage tank or group of containers. It helps capture leaks and spills before they reach soil, groundwater, storm drains, sewers, waterways, or occupied areas.

For facilities that store hazardous materials, choosing the right secondary containment system is an important part of spill prevention and environmental protection.

However, secondary containment requirements are not identical for every tank or facility. Requirements can depend on the material stored, tank configuration, facility operations, and applicable federal, state, and local regulations.

What Is Secondary Containment?

Secondary containment is a protective system installed around a primary storage tank or container.

The primary tank stores the material under normal operating conditions. If the primary tank leaks or loses its integrity, the secondary containment system provides another barrier to help control the released material.

Common secondary containment systems include:

• Concrete containment areas
• Dikes and berms
• Containment basins
• Spill curbing
• Lined containment areas
• Containment pallets for smaller containers
• Double-wall tanks with an interstitial space
• Other engineered containment or diversionary systems

The appropriate solution depends on the tank, stored material, facility layout, environmental conditions, and applicable regulations.

Why Is Secondary Containment Important?

A tank failure can release a significant volume of liquid in a short period. Without adequate containment, the released material can travel across a facility and enter areas that are difficult or expensive to clean.

Secondary containment can help facilities:

• Limit the spread of spills
• Protect soil and groundwater
• Reduce the risk of environmental releases
• Prevent incompatible materials from mixing
• Protect storm drains and drainage systems
• Improve spill-response operations
• Reduce potential cleanup costs
• Support regulatory compliance
• Protect workers and surrounding property

For oil-storage facilities subject to the EPA’s Spill Prevention, Control, and Countermeasure (SPCC) requirements, appropriate containment or diversionary structures are required to prevent discharges.

Which Industrial Tanks May Need Secondary Containment?

Secondary containment can apply to many types of industrial storage systems.

Examples include:

• Above-ground chemical storage tanks
• Oil storage tanks
• Fuel storage tanks
• FRP storage tanks
• Polyethylene storage tanks
• Carbon steel tanks
• Stainless steel tanks
• Alloy tanks
• Waste storage tanks
• Industrial wastewater tanks
• Oil-filled equipment
• Groups of bulk storage containers

The exact requirements depend on the application and the regulations that apply to the facility.

For example, EPA’s SPCC requirements apply to certain non-transportation-related facilities based on factors such as aggregate oil storage capacity and the reasonable expectation of a discharge to navigable waters or adjoining shorelines.

Therefore, facilities should evaluate the applicable regulations before selecting a containment design.

Types of Secondary Containment Systems

Different facilities use different containment methods. The best solution depends on the tank design, material stored, available space, and site conditions.

1. Concrete Containment Areas

Concrete containment areas can surround one or more tanks.

They can provide a durable barrier when properly designed and maintained. However, the concrete must be compatible with the stored material. In some applications, the containment area may also require a protective coating or liner.

Cracks, joints, penetrations, and drainage points require careful attention because they can become potential leak paths.

2. Dikes and Berms

Dikes and berms create a raised barrier around a tank or storage area.

They can work well for outdoor tanks and large-volume storage applications. The containment area must provide enough usable capacity and should account for factors such as precipitation when required by the applicable regulation.

3. Containment Basins

A containment basin provides a defined area for collecting leaked or spilled material.

Facilities can construct basins from concrete, steel, fiberglass, or other chemically compatible materials, depending on the application.

4. Double-Wall Tanks

A double-wall tank contains the primary tank inside a second wall.

The space between the two walls provides an additional barrier. Some double-wall systems also include leak detection.

This design can reduce the need for a separate external containment structure in certain applications. However, facilities must still evaluate applicable regulations and site-specific requirements.

5. Lined Containment Areas

A liner can provide additional protection where the underlying construction material may not provide sufficient chemical resistance.

The liner material should match the chemical characteristics of the stored product.

Compatibility matters because some chemicals can attack coatings, plastics, concrete, or other containment materials.

Secondary Containment Material Compatibility

Secondary containment should not simply be strong. It must also be compatible with the material it may need to contain.

Consider factors such as:

• Chemical concentration
• Chemical composition
• Operating temperature
• Exposure time
• UV exposure
• Abrasion
• Corrosive properties
• Potential reaction with the containment material

For example, a containment system designed for water may not be suitable for a concentrated chemical.

Likewise, a material that performs well at ambient temperature may not provide the same performance at elevated temperatures.

Therefore, material compatibility should be evaluated as part of the tank and containment design.

How Much Secondary Containment Capacity Is Required?

This is one of the most important questions when designing a containment system.

There is no single containment percentage that applies universally to every industrial storage tank in every regulatory situation.

The required capacity depends on the applicable regulation and the type of material or facility involved.

For example, EPA’s SPCC requirements for bulk storage container installations require secondary containment for the capacity of the largest single container, along with sufficient freeboard to contain precipitation. EPA states that facilities should consider precipitation when determining adequate containment capacity.

Other regulatory programs can use different sizing requirements.

For example, certain hazardous-waste tank requirements use a 110% design-capacity criterion for the largest tank within the containment boundary and address precipitation separately.

Some state requirements also establish specific containment-volume criteria.

Because of these differences, facility owners should not assume that a single 110%, 150%, or 10% calculation applies to every project.

The applicable regulation should determine the required containment capacity.

Example: Calculating Containment Capacity

Suppose a facility has several tanks in one containment area.

The design team should first determine:

1. The capacity of each tank.
2. Which regulation applies.
3. Whether the regulation requires containment based on the largest tank, aggregate capacity, or another criterion.
4. Whether precipitation must be included.
5. Whether the containment area can prevent overflow.
6. Whether the containment material is compatible with the stored liquid.

For an SPCC-regulated bulk storage installation, EPA requires containment for the largest single container plus sufficient freeboard for precipitation.

This approach is more reliable than applying a generic percentage without considering the regulatory context.

Secondary Containment for Multiple Tanks

A common industrial installation may contain several tanks in the same area.

A shared containment system can be practical when the tanks store compatible materials and the containment design meets applicable requirements.

However, facilities should consider the consequences of a simultaneous release or the mixing of incompatible chemicals.

For example, storing two chemicals inside the same containment area may create an additional hazard if the chemicals react when mixed.

Therefore, tank grouping should consider:

• Chemical compatibility
• Tank capacity
• Spill pathways
• Drainage
• Containment capacity
• Fire hazards
• Emergency response
• Regulatory requirements

EPA also recognizes that multiple containers can use a common containment or collection area under applicable SPCC requirements rather than requiring separate containment for every individual container.

Secondary Containment for Chemical Storage Tanks

Chemical storage requires special attention because a spill can create more than an environmental problem.

A released chemical can:

• Corrode equipment
• Damage concrete
• React with another chemical
• Create toxic vapors
• Create a fire hazard
• Damage nearby piping and electrical equipment
• Enter stormwater systems
• Create worker-safety risks

For this reason, the containment material should be compatible with the chemical.

The containment design should also consider the chemical’s concentration, temperature, and expected exposure duration.

Facilities should review the Safety Data Sheet (SDS) and applicable engineering requirements when evaluating chemical containment.

Secondary Containment for Above-Ground Storage Tanks

Above-ground storage tanks can provide easier access for inspection and maintenance. However, a leak from a large above-ground tank can spread quickly across a facility.

A secondary containment area can help control that release.

When designing containment for an above-ground tank, consider:

• Tank capacity
• Tank diameter and footprint
• Containment-wall height
• Available free volume
• Precipitation
• Drainage
• Tank connections
• Valves and piping
• Transfer areas
• Access points
• Inspection requirements
• Chemical compatibility

For outdoor installations, precipitation can significantly affect the usable capacity of the containment area. EPA specifically addresses freeboard for precipitation under its SPCC bulk-storage requirements.

Secondary Containment and Stormwater

Stormwater creates an important design consideration for outdoor containment.

Rainwater can accumulate inside a containment area and reduce the available volume.

Therefore, facilities need a suitable method for managing accumulated precipitation without allowing contaminated water or spilled material to escape.

EPA guidance recommends maintaining adequate containment capacity and provides specific considerations for precipitation under the SPCC rule.

Facility operators should also follow applicable procedures before releasing accumulated water from a containment area.

Inspection and Maintenance of Secondary Containment

Installing containment is only the first step.

The system should remain functional throughout the life of the tank.

Regular inspections should look for:

• Cracks
• Corrosion
• Damaged liners
• Deteriorated coatings
• Failed seals
• Open or damaged drains
• Structural damage
• Blocked drainage paths
• Chemical deterioration
• Accumulated liquids
• Vegetation or debris
• Damaged containment walls

EPA’s SPCC guidance also addresses inspection, evaluation, and testing of equipment and containment systems.

Facilities should document inspections and correct deficiencies promptly.

Common Secondary Containment Mistakes

Several design and maintenance mistakes can reduce the effectiveness of a containment system.

Using the Same Material for Every Chemical

A containment material that works for one chemical may fail when exposed to another.

Better approach: evaluate chemical compatibility before selecting the containment material.

Ignoring Precipitation

Outdoor containment areas can lose available capacity when rainwater accumulates.

Better approach: account for precipitation and follow the requirements of the applicable regulatory program.

Treating a Generic Percentage as a Universal Rule

Different regulations can establish different containment requirements.

Better approach: identify the applicable federal, state, and local requirements before finalizing the design.

Allowing Uncontrolled Drainage

An open drain can allow spilled material to escape the containment area.

Better approach: design drainage and release points so they do not defeat the containment system.

Neglecting Cracks and Coating Damage

A damaged containment structure may not perform as intended during a spill.

Better approach: inspect containment areas regularly and repair deficiencies promptly.

Secondary Containment vs. Double-Wall Tanks

Secondary containment and double-wall tanks provide additional protection, but they use different approaches.

A conventional secondary containment system creates a separate containment area around the primary tank.

A double-wall tank incorporates the additional barrier into the tank itself.

The appropriate solution depends on:

• Tank size
• Material stored
• Site limitations
• Installation requirements
• Leak detection requirements
• Applicable regulations
• Project cost
• Maintenance requirements

In some applications, a double-wall tank may be practical. In others, an external containment system may provide a better solution.

The design should match the specific application rather than relying on a one-size-fits-all approach.

Regulatory Considerations for Secondary Containment

Industrial facilities may need to comply with several layers of regulation.

Depending on the application, these can include:

• Federal requirements
• State environmental regulations
• Local regulations
• Fire codes
• Building codes
• Occupational safety requirements
• Industry-specific standards
• Facility-specific permits

For example, the EPA’s SPCC rule applies to certain non-transportation-related facilities that meet specified oil-storage and discharge-risk criteria.

Underground storage tanks can fall under different regulatory requirements. EPA’s UST requirements include specific secondary-containment and interstitial-monitoring provisions for certain new and replaced tanks and piping.

Therefore, facility owners should identify the regulations that apply to their specific tank system before selecting the containment design.

How GSC Tanks Can Help With Industrial Tank Projects

Selecting the right storage tank involves more than choosing a capacity.

The tank material, stored product, operating conditions, tank configuration, site requirements, applicable standards, containment strategy, and maintenance requirements all influence the final solution.

GSC Tanks provides industrial storage tank solutions in materials including fiberglass/FRP, polyethylene, carbon steel, stainless steel, alloy, and reinforced concrete, allowing tank selection to match different industrial applications.

For a new tank project, facilities should evaluate the complete system rather than considering the primary tank alone.

That includes:

• Primary tank design
• Material compatibility
• Tank capacity
• Tank configuration
• Secondary containment
• Piping and fittings
• Linings and coatings
• Installation requirements
• Inspection and maintenance

Secondary Containment Checklist

Before finalizing an industrial tank project, review the following:

• Identify the material being stored.
• Confirm the tank capacity.
• Determine the applicable regulations.
• Evaluate chemical compatibility.
• Select an appropriate containment material.
• Determine required containment capacity.
• Consider precipitation for outdoor installations.
• Review drainage and discharge points.
• Consider incompatible materials stored nearby.
• Evaluate tank connections and transfer areas.
• Establish inspection procedures.
• Plan for spill response.
• Document the containment design and supporting calculations where appropriate.

Frequently Asked Questions

What is secondary containment for an industrial storage tank?

Secondary containment is an additional barrier around a tank or group of containers. It helps capture leaks and spills from the primary tank and reduces the risk of uncontrolled releases.

Is secondary containment required for every industrial tank?

Not necessarily. Requirements depend on the stored material, tank type, facility operations, and applicable federal, state, and local regulations.

How much secondary containment is required for a storage tank?

There is no universal percentage for every industrial tank. The required capacity depends on the applicable regulatory program and project conditions. For example, EPA SPCC requirements for bulk storage address the capacity of the largest single container plus sufficient freeboard for precipitation.

Is 110% secondary containment always required?

No. 110% should not be treated as a universal requirement for every industrial tank. Different regulations and applications use different containment criteria.

What materials can be used for secondary containment?

Common materials include concrete, steel, fiberglass, liners, coatings, and other chemically compatible materials. The correct material depends on the stored substance and operating conditions.

Can multiple tanks share one secondary containment area?

Yes, in appropriate applications. However, the design must account for the tanks’ capacities, stored materials, chemical compatibility, drainage, and applicable regulatory requirements. EPA’s SPCC guidance allows common containment arrangements for multiple containers in certain circumstances.

Does secondary containment need to account for rainwater?

For many outdoor applications, precipitation can affect available containment capacity. Applicable regulations should determine how precipitation and freeboard must be addressed. EPA specifically considers precipitation in its SPCC bulk-storage containment requirements.

What happens if secondary containment is damaged?

Cracks, corrosion, failed liners, or damaged containment walls can reduce the system’s ability to contain a spill. Facilities should inspect containment systems regularly and repair deficiencies promptly.

What is the difference between secondary containment and a double-wall tank?

Secondary containment generally uses a separate barrier around the primary tank. A double-wall tank incorporates a second wall into the tank structure itself. The appropriate solution depends on the project and applicable requirements.

Conclusion

Secondary containment plays an important role in responsible industrial liquid storage.

However, effective containment requires more than simply building a wall around a tank. The design must consider the stored material, tank capacity, chemical compatibility, precipitation, drainage, site conditions, and applicable regulations.

Most importantly, facilities should avoid applying a generic containment percentage to every project. Regulatory requirements can vary significantly by application.

A properly selected tank and containment system can help facilities reduce spill risks, protect the environment, support regulatory compliance, and improve overall facility safety.

For industrial storage tank projects, working with an experienced tank manufacturer can help ensure that the tank, materials, configuration, and containment strategy work together as part of the overall system.

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