Hydraulic conductivity is commonly estimated from grain size characteristics of unconsolidated sediments. We present an extensive set of air-permeability and grain size measurements from a heterogeneous aquifer. These data are unique in that the hydraulic conductivity measurements are made on undisturbed in-situ sediment and, like the grain size measurements, have a small sample volume size (<1200 cm3). Hydraulic conductivity estimated from grain-size has a higher mean and a lower variance than direct measurements. While grain size estimates of hydraulic conductivity do not correspond well to field measured hydraulic conductivity, spatial correlation of the two data sets is a quite similar.