A bunded zone features a low wall encircling the storage vessel, either above ground or sunk into a pit. The wall and the floor area within it are lined and fully sealed to prevent leakage, and are constructed from materials that will chemically resist the stored contents. A bunded zone can contain any number of storage vessels, providing the contents of all vessels are compatible with each other and will not cause a hazardous chemical reaction if they come into contact. For this reason, a bunded zone is a more cost-effective option than several separate bunded tanks as the storage tanks can be single-skinned.