Secondary containment is required for which UST systems?

Secondary containment is a crucial safety feature for various underground storage tank (UST) systems, primarily designed to prevent the release of hazardous substances into the environment in the event of a primary containment failure. The correct answer identifies that Category 3 UST Systems and their associated piping specifically require secondary containment to enhance environmental protection.

Category 3 UST Systems refers to those that may pose a greater risk of product release due to their operational characteristics or the environment they are in. For example, if these systems are located near sensitive areas, such as groundwater sources, the additional layer of protection provided by secondary containment becomes critical. This containment can be a double-walled tank design or a separate containment structure that can capture leaks or spills, thus preventing contamination.

This requirement is not universally applied to all UST systems, which is why the other choices do not fit. Some UST systems might not be categorized under Category 3 or may have smaller storage capacities, which leads to different regulatory requirements regarding containment measures. Therefore, focusing on Category 3 UST systems highlights the need for increased safety protocols where there is a heightened potential risk.