Storage tanks are underground and aboveground structures of different shapes, sizes and designs. These structures can have volumes ranging from 5 to 120,000 m3. Refined oil products are generally kept in steel tanks as well as tanks made of reinforced concrete with oil product resistant internal steel cladding. Petroleum and heavy oil products are normally stored in reinforced concrete tanks. Stainless steel structures are employed where storage requirements are particularly high, such as for potable water. Horizontal tanks are supplied to their installation site already assembled. They are used for transport and storage of oil products at oil distribution terminals and active on-site depots.