The purpose of a tank foundation is to provide a level surface for the tank and to equally transmit the load of the tank and its contents to the soil. The tank foundation elevates the floor of the tank above grade which will minimize the amount of corrosion that the tank will see. The tank foundation is usually concrete placed on compacted soil. The foundation can be a concrete ring that is filled with pebble granite or sand.
Alternatively, a concrete slab can be used. A concrete slap type foundation can be designed such that observation channels are built into the foundation. If the floor of the tanks leaks, the liquid will flow through the channel to make identification easier.
The foundation must sit on compacted soil or settling may occur which, in extreme cases, could cause the tank to overturn during a seismic event. Regardless of the type of foundation used, the outer part of the foundation is called the shoulder. The purpose of the shoulder is to support the tank wall.