A bund may not be necessary if the site is isolated from the drainage system, I used to work on a chemical site where this was the case. There could be underground containment to protect against spills contaminating the environment.
You could also have a some sort of gauge or other indicator showing how full it is, either a analogue needle on a scale (like a petrol gauge in a car) or a lcd display showing the contents in litres or kgs etc. We used both.
Martin