Secondary containment requirements
Secondary containment requirements for aboveground fuel tanks
Start with the rule that applies to the facility. For EPA SPCC bulk storage, the sizing test is the entire capacity of the largest single container plus sufficient freeboard for precipitation, not a universal percentage.
Buyer impact
What the SPCC containment sizing rule actually says
EPA's SPCC rule uses rated container capacity, not the amount you normally keep in the tank. A common containment area serving multiple tanks is sized around the largest single container and the required precipitation freeboard, provided the overall design satisfies the rule.
Worked planning example
Two 2,000-gallon tanks inside one outdoor containment area
For the federal SPCC bulk-storage sizing test, start with 2,000 gallons, the capacity of the largest single container, then add sufficient freeboard for precipitation. Do not simply multiply total site gallons by a generic 110% rule. Final geometry and freeboard should be confirmed for the actual site and governing requirements.
Secondary containment has more than one regulatory purpose
EPA SPCC is an environmental spill-prevention rule. Fire-code, state, and local programs can separately address tank construction, drainage, spacing, dispensing, and site protection. Meeting one layer does not automatically satisfy the others.
Double-wall tanks can be part of the containment strategy
A double-wall tank provides a secondary shell around the primary tank and an interstitial space that can be monitored for leakage. Whether that construction fully satisfies a specific site's containment obligations depends on the SPCC Plan and any separate state, fire-code, or AHJ requirements.
Read the double-wall fuel tank guide →
Berms, dikes, and common containment still have a place
Site-built containment can make sense around larger tanks, tank farms, or facilities where one containment area serves several containers. Outdoor systems also need operating practices for accumulated precipitation and drainage so required capacity is preserved.
Five containment mistakes that create redesigns
- Using a generic percentage without checking the governing rule.
- Sizing to normal operating volume instead of rated container capacity where full capacity is required.
- Ignoring precipitation freeboard outdoors.
- Assuming “double wall” automatically satisfies every environmental and fire-code requirement.
- Forgetting transfer areas, piping, and dispensing release pathways addressed elsewhere in the facility's spill-control program.
Turn the rule into a tank and site decision
What not to assume
- Do not use a generic 110% shortcut without checking the actual governing rule.
- Do not assume double wall automatically satisfies every site or facility requirement.
- Do not ignore precipitation, drainage, or transfer-area release paths in the containment plan.
Primary sources
- U.S. EPA: Secondary Containment for Each Container Under SPCC
- U.S. EPA: Does SPCC Apply to Your Facility?
- UL Solutions: Aboveground Tank Certification Guide
Trying to choose a containment approach?
Send the tank size, number of tanks, site location, and whether the project is dispensing fuel. We can help identify the questions to resolve before you build a berm or buy a double-wall tank.
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