Are you building or growing? Here's some info on clay soil.
http://extension.oregonstate.edu/gardening/how-improve-clay-soil
http://extension.oregonstate.edu/gardening/how-improve-clay-soil
https://en.wikipedia.org/wiki/UltisolUltisols can have a variety of clay minerals, but in many cases the dominant mineral is kaolinite. This clay has good bearing capacity and no shrink–swell property. Consequently, well-drained kaolinitic ultisols such as the Cecil series are suitable for urban development.