Lunne et al (1997) suggested an approximate method to estimate soil permeability (hydraulic conductivity) from the CPT via the Soil Behavior Type (SBT) chart using non-normalized cone resistance and friction ratio. This was based on the basic observation that sands typically have high permeability and clays low permeability and that the CPT can be used to estimate soil type and hence, soil permeability. However, Lunne et al (1997) suggested a wide range of values for soil permeability in any given soil type. In recent years, increasing use has been made of the Soil Behavior Type Index (Ic) using normalized CPT results as a means to vary empirical correlations as a function of soil type. This can also be applied to the correlation between soil type and permeability to produce the following simplified relationship: