What depth of cover is required for backfill material in traffic areas according to NFPA 30?

The requirement of 3 feet of earth as the depth of cover for backfill material in traffic areas, according to NFPA 30, ensures the protection of underground storage tanks from mechanical damage that could be caused by vehicles. This depth provides sufficient weight and insulation to shield the tanks from stress that may occur from the movement of heavy equipment or vehicles on the surface.

In traffic areas, the risk of puncture or impact increases significantly, making it imperative to have a robust layer of earth above the tanks. NFPA 30 guidelines are based on safety assessments that suggest this depth is optimal for minimizing risks while also considering construction feasibility and the integrity of the tanks.

Having a cover depth that is either too shallow or too deep could lead to vulnerabilities or unnecessary complications, such as challenges in maintenance or increased costs without proportional benefits. Therefore, the 3-foot requirement balances these factors to ensure safety and practicality in the management of underground storage tanks in areas with traffic.