Expansive soils shrink when dry and swell when wet. This movement can exert enough pressure to crack sidewalks, driveways, basement floors, pipelines and even foundations. Pressures can be as great as 15,000 pounds per square foot. Expansive soils are found throughout Colorado. Parts of the major population centers along the Front Range and on the West Slope are located on expansive soils.
Soil surveys provide general information about soils in an area.
They are available from the Natural Resources Conservation Service, U.S. Department of Agriculture. However, maps provide only generalized locations. Before construction, test the soil on a specific site. Not all expansive soils have the same swell potential. Tests can determine the swell potential of a particular soil and the probability for structural damage.