The Greys series consists of very deep, well drained soils that formed in loess and silty alluvium from loess. These soils are on foothills, fan terraces, ground moraines, and mountain footslopes. Slopes are 1 to 30 percent.
Permeability is moderately slow.
Greys silt loam, quaking aspen. There are no other series in the same family. Similar series are the Willow Creek , Bozeman , Lanark , and Robana series. Willow Creek soils lack E horizons. Bozeman, Lanark and Robana soils have mollic epipedons greater than 16 inches thick.