Secondary Containment Guidelines

In an effort to reduce or eliminate environmental contamination, secondary containment is required by law for all regulated hazardous materials. Secondary containment is one step in a multi-tiered approach to environmental protection that includes stage one and stage two vapor recovery as well as spill prevention.

What is it

It is a system set in place to protect the environment from spillage, overfill, or leakage from storage tanks housing hazardous materials. Typically, secondary storage will be a dike system, concrete vault, or double wall steel storage tank. These secondary systems must have sufficient volume to hold all of the primary tank’s liquid capacity plus a hefty extra percentage to ensure proper containment.

Secondary Containment Guidelines

When storing and dispensing hazardous materials, great care must be taken to contain and spills or leakages that may occur. To ensure continued environmental protection and health, the EPA has set forth guidelines regarding the proper implementation of secondary containment.

Secondary Containment Volume

The secondary volume of a single storage tank must be at least 110% of the tank. Facilities with more than one tank must have secondary containment of at least 150% of the largest tank’s volume or 10% of the total volume of all containers, whichever is greater.

If the secondary system is open to rainfall, the system must be hold at least 4.5 inches of rainfall over the required containment volume. Secondary containment systems open to fire sprinklers must hold the water from said sprinklers for at least 20 minutes while still maintaining the required containment volume.

Secondary Containment Construction

The containment system must be constructed of materials that, at the least, can contain any spills or leakages between inspection periods.

Overfill Protection

Overfill protection must be provided in some form for the tank’s primary containment vessel. Overspill protections devices can include:

  • High-level alarms
  • Over spill buckets
  • Sump pumps

Material Separation

Materials that may hazardous conditions such as fires and explosions, production of flammable or toxic gases, or primary or secondary tank containers when mixed must be separated in both the primary and secondary to avoid intermingling of these substances.


Drainage from this type of containment systems must be controlled at all times. Rainwater or sprinkler discharge collected by the secondary containment system must be found to be environmentally safe before it can be released. Drainage systems must remain closed, and pumps must be off if the drainage process is un-monitored.

Things to Remember

  • Keep storage areas locked at all times. Unauthorized access may lead to injury or storage tank damage.
  • Cover secondary containment systems to prevent rainfall entry.
  • Test secondary containment systems regularly to ensure they are sealed tight.
  • Surfaces must be coated with approved products to protect the containment system’s surface.
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