What component may be included in underground storage systems alongside the tank?

Vapor-recovery piping and equipment is an essential component of underground storage systems alongside the tank. This system is crucial for managing vapors that may be released during the filling, dispensing, and storage of fuel and other volatile liquids. The vapor recovery system captures and recycles vapors that would otherwise escape into the atmosphere, thereby reducing air pollution and enhancing safety by minimizing the risk of explosion or fire due to flammable vapors.

Vapor recovery is especially important in maintaining compliance with environmental regulations that aim to control emissions from storage tanks. This equipment works in conjunction with the tank to ensure that any vapors generated are processed and reused rather than vented.

Other components mentioned, while important in different contexts, do not typically accompany underground storage tanks in the same way. Electrical wiring may be necessary for operational systems, but it is not a primary component directly related to the storage and containment function. An overfill prevention system is critical for preventing spills during tank filling, but it is a separate device rather than a component that sits alongside the tank. Ventilation ducts are not usually part of underground storage systems as they pertain more to building air management.