In traffic areas, what is the required inches of compacted backfill and paving between the top of piping and grade?

In traffic areas, the requirement for compacted backfill and paving is set to ensure that underground storage tank (UST) systems, particularly the piping, are adequately protected from potential damage due to vehicle traffic. The correct requirement is 18 inches of compacted backfill and paving between the top of the piping and the ground grade.

The primary reason for this specification is safety and structural integrity. A minimum of 18 inches helps to distribute the load from traffic above, minimizing the risk of stress on the piping that could lead to cracking or failure. This distance also allows for adequate soil cover, which can absorb and dissipate some of the impact from traffic, providing a buffer against the stresses that might be applied to the piping.

When considering the other options, while they may seem reasonable, they do not meet the specific standards and guidelines intended for maintaining the durability and operational safety of underground storage systems in areas subject to vehicular traffic. The 18-inch requirement creates a balanced approach that addresses both safety and practicality for UST systems.