Abstract: A secondary containment structure for the safe storage of hazardous materials held in primary containers, such as drums, cans and bottles. In large sizes, the containment structure is adapted to function as a pallet or as the floor of a building or shelter for primary containers. The structure includes a core formed of an end-grain balsa wood base and a rectangular frame placed thereover formed of the same or similar material to define the bed and the side walls of a sump. The inner edges at the upper end of the frame are indented to create a ledge to accommodate a fiberglass grating. The containers to be stored are seated on the grating, whereby leakage or spillage from the containers are collected in and confined to the sump. Laminated to the exposed surfaces of the core is a layer of a fiberglass-reinforced plastic material, whereby the resultant laminate, though light in weight, is of exceptional strength.