In the eastern United States, auger mining is used on hillside terrain. It requires a surface cut to allow the auger access to the coal. It is also used to recover part of the coal left from underground mining. Auger mining is mostly used in conjunction with strip mining. Coal mining by the auger method entails boring horizontal or near-horizontal holes in an exposed face of the coal and loading the coal removed by the auger. Single, dual, or triple auger heads can remove up to 90 inches of coal for over 200 feet. Augering is used to supplement recovery at contour or strip mines when the overburden becomes too great to be economically removed. It is also used where the terrain is too steep for overburden removal and where recovery by underground methods would be impractical or unsafe.