Goodbye, Hazen; Hello, Kozeny-Carman

The century-old Hazen formula for predicting the permeability of sand is based only on the D10 particle size. Whereas, the half-century-old Kozeny-Carman formula is based on the entire particle size distribution, the particle shape, and the void ratio. As a consequence, the Hazen formula is less accurate than the Kozeny-Carman formula. It is recommended that the former be retired and the latter be adopted.