Hello everyone. Is a permeability value of 100ft/day (0.35mm/s) typical for a free draining soil?. Is not this value too low? The CALTRANS design guide has this value when identifying a free draining soil, but I believe it is too low (especially when the minimum permeability values recommended for a drainage layer in the DG 2002 is 1000ft/day). Could this be an error in the Caltrans guide, or is this correct? What is a typical permeability value range for a free draining soil? Thank you very much for any help/information on this matter.
http://physics.uwstout.edu/geo/perm_dewat.htm For a discussion of permeability. Coarse gravel has a permeability factor of less than 1/10th of a cm/sec. (high) Clean sand 0.1 to 0.001 cm/sec (medium) Dirty sand 0.001 to 0.00001 cm /sec (low) Silt 0.00001 to 0.0000001 cm/sec (very low) Clay less than 0.0000001 cm/sec (impervious) Check the Design Guide for what factor is being described.