An investigation was conducted to characterize the hydraulic conductivity of a shallow clay till aquitard over which a municipal solid waste landfill was being sited. Hydraulic conductivity tests were conducted in the laboratory on specimens removed from the till in thin-wall sampling tubes (71 mm diameter) and as large hand-carved blocks (460 mm diameter). Field hydraulic conductivity was measured using a slug test. Tests on specimens from the sampling tubes indicated that the hydraulic conductivity of the till was very low (10⁻⁹ to 10^-8 cm/s). The slug test and tests on large blocks containing fractures yielded much higher hydraulic conductivities, on the order of 10⁻⁶ cm/s. This difference in hydraulic conductivities is attributed to fractures, which were evident in the block specimens. Testing of the block specimens at higher overburden stresses showed that the hydraulic conductivity decreased by one order of magnitude as the overburden stress increased from 35 kPa to 175 kPa, apparently due to closure of the fractures.