Originally developed to deter grave robbers in the late 19th century, vaults are required today by many cemeteries in order to help prevent the ground from sinking and markers from moving. There are no state or federal laws requiring the use of a vault, though cemeteries are allowed to have policies that do. Some conventional cemeteries now offer consumers the option of paying additional amounts of money in an endowment care funds to handle potential maintenance associated with vaultless burial. Many however, offer vaultless burial at no additional charge. While the concrete and metal in vaults are considered "natural" to some, the manufacturing and transporting of vaults utilizes a tremendous amount of energy and contribute to 1.6 tons of reinforced concrete being produced. Vaults are not required in GBC approved Hybrid Burial Grounds and prohibited in Council certified Conservation and Natural Burial Grounds.