A vault is essentially a large box made out of concrete. Originally developed to deter grave robbers in the late 18th century, vaults are sold today as being necessary to keep the ground from sinking and markers from moving. For many years, this kind of settling was dealt with by mounding extra dirt atop a grave and renovating the soil. There are no state or federal laws that require the use of a vault, though a cemetery can insist that one be used. Many cemeteries now make vaults a requisite for burial. Vaults cause Americans to bury each year 1.6 million tons of reinforced concrete. And vaults that drain out the bottom can cause toxins and heavy metals from to go into the ground, and sometimes ground water, at much higher levels than if they were not used.