Abstract: The Invention is an underground storage tank apparatus and method. A buried underground storage tank has a tank sump and a manway defined by a manhole skirt side wall communicating from the surface of the ground to the tank sump. A sediment trap is disposed annularly within the manway and intercepts water and sediment flowing down the manhole skirt wall. An inside wall of the sediment trap is in an annular spaced-apart relation with a tank sump perimeter watt, which together define an annular space interior volume that receives water that overtops the sediment trap inside wall and which receives liquid that overtops the tank sump perimeter wall.