The BBC and the Dome Corporation of America say that rock salt storage facilities are in the shape of domes so that trucks can easily enter and leave the storage area without having to go around trusses or roof supports. Structures with domes have high interior spans that give bulldozers and dump trucks room to move around.
Large doors on the front of storage units keep the rain out. Because salt is corrosive, salt storage areas with domes are made of things like protected concrete, wooden beams, and roof shingles. More than 19,000 tonnes of sand can fit inside a concrete dome with a diameter of 150 feet and walls that are 12 feet high. The BBC says that larger salt storage facilities in Great Britain can hold between 2,000 and 3,000 metric tonnes of salt.