A containment system comprising a flexible bladder having at least one opening through which a liquid or other fluid or material can be pumped or transferred into or out of the bladder. The bladder has a contracted and an expanded or semi-expanded state. A support structure surrounds the side surfaces of the bladder and provides lateral support to the bladder when the bladder is in an expanded or semi-expanded state. The support structure comprises a plurality of panels that are seperably connected to one another to form an enclosed walled support structure. The at least one opening in the bladder is operatively connected to a point exterior to the support structure to permit the bladder to be filled or evacuated from a position exterior to the support structure.