Level fields can be drained as long as minimum grades of 0.05 to 0.1% are maintained for tile laterals. A tile at 0.1% grade has 1 foot of fall per thousand feet. On level ground this means that the tile depth would vary by 1 foot over 1000 ft. A typical drainage system provides an outlet where tile can drain freely (by gravity) into a surface ditch. Where topography does not allow for a gravity outlet, pumped outlets are used, provided a surface waterway exists to discharge the drainage water. A pumped outlet or "lift station" provides the lift required to get the drainage water from the elevation of the tile, to the ground surface and into the receiving waterway. Pumped outlets add to the initial outlay and operation/maintenance costs of the drainage system, but have proven to be economically feasible in many situations. A pumped outlet station includes sump, pump, and discharge pipe. Important design features include size and shape of sump and capacity of the pump.