What is "phase separation," and how can it occur in USTs?

Phase separation refers to the phenomenon where water and gasoline separate from each other within an underground storage tank (UST). This occurs when water enters the tank, often due to leaks, rainfall, or condensation, leading to a distinct separation of the gasoline and water layers. The gasoline, being lighter, floats on top of the water.

When phase separation happens, it significantly impacts fuel quality and usability. The presence of water in the fuel can cause engine performance issues, as water does not combust, leading to potential damage to engines and other fuel handling equipment. Understanding this process is critical for UST operators in order to implement proper monitoring and maintenance practices to prevent phase separation and ensure compliance with environmental regulations.

Other options do not accurately describe phase separation; for example, mixing different fuels does not pertain to the separation process, and phase separation is not a technique used to enhance fuel efficiency. Additionally, while reactions with tank materials may affect fuel quality, it is not the same as the phase separation process caused specifically by water intrusion.