In what situation is it mandated to provide secondary containment for aboveground tanks?

Providing secondary containment for aboveground tanks is mandated particularly in situations where there is a risk of high intensity liquid pool fires. The reasoning behind this is centered on safety and environmental protection. High intensity fires can lead to significant damage and pose a threat to both life and property, especially if a flammable liquid were to spill or leak from the tank. Secondary containment systems, such as dikes or double-walled tanks, help ensure that any spilled liquid is contained, preventing the spread of fire and mitigating environmental harm.

In scenarios where tanks are situated indoors, while safety considerations are critical, the mandate for secondary containment is often tied to the nature of the substance contained and the specific risks associated with it, rather than the location alone. Similarly, tanks used for non-flammable liquids may necessitate different safety measures that do not always include secondary containment, thus making the specific risk associated with flammable materials central to the requirements. The threshold of 100 gallons indicates capacity but does not inherently dictate containment requirements without consideration of the risks involved.