Abstract: A secondary containment and drainage system for an above-ground storage tank is described, in which small quantities of leaked or overflowing liquid are temporarily stored in a housing above the internal storage tank. This fluid can be easily removed from the housing for re-use or at least removed without the time consuming process of emptying and cleaning the overfill dike that surrounds the tank. When greater quantities of liquid leak from the input port of the storage tank, the overflowing liquid is drained into the dike through a drainage pipe that extends from the housing, through the internal storage tank, and into the dike. The dike is enclosed by a roofing structure that forms a seal to prevent contamination when liquid is drained into the dike.