To qualify as an "Underground Storage Tank", the volume of the tank and pipes must be what percentage or more below the surface?

To qualify as an "Underground Storage Tank" (UST), the definition typically requires that at least 10% of the tank's total volume, including any associated piping, must be located below the surface of the ground. This definition is set forth by the Environmental Protection Agency (EPA) and under various state regulations governing underground tanks. The purpose of this classification is to distinguish USTs from above-ground storage tanks, which pose different risks and regulatory requirements.

The 10% threshold is significant because it recognizes the potential environmental risks posed by tanks that are predominantly buried. Tanks that meet this percentage are subject to stringent regulations and oversight to ensure the safe containment of hazardous materials and to prevent soil and groundwater contamination.

Understanding this threshold is crucial for compliance with environmental laws and regulations, ensuring proper management and mitigation of any potential risks associated with the storage of hazardous substances underground.