Wall-type bunds / dikes for storage compounds should be from 0.5 m to 1.5 m high (1.5 ft. - 5 ft. - check local codes and regulations), depending on the required containment capacity and the distance to the container. The closer the wall to the container, the higher the wall has to be.
If the liquid to be stored is classed as a dangerous substance, make an allowance for the trajectory of a liquid leak, assuming a full tank with an elevated point of leakage. You might need to install a splatter shield, or have a generous distance between the tank and the bund / dike wall; half the height of the tank would be appropriate.
For solids storage compounds, it is important to consider the transfer equipment requirements. For example, conveyors are constrained by maximum gradients so may require greater distances to climb over bund / dike walls.