Experiments conducted to quantify potential leakage from holes in two geomembranes [1-mm-thick linear low-density polyethylene (LLDPE) and 2-mm-thick high-density polyethylene (HDPE)] placed on a silty-sand [underliner hydraulic conductivity (kUL), 1.1x10-7kUL1.2x10-5m/s], or pea gravel (kUL=1x10-2m/s) underliner (foundation/subgrade) and covered with saturated fine tailings at 65% initial solids content are discussed [tailings hydraulic conductivity (kT), 2.9x10-8kT1.6x10-6m/s]. Tests results show that the overlying tailings, with a kT<kUL, filled the geomembrane hole and had a larger effect on flow through the hole than the underliners examined. For the tested conditions, leakage through 10 and 20-mm-diameter holes were essentially the same whereas the leakage through a 1.5-mm-diameter hole was three orders of magnitude lower. Introduction of a 580g/m2 nonwoven needle-punched geotextile (GTX) layer between the geomembrane and tailings increased the flow by approximately 60%. A gap below geomembrane hole attributable to a stone on the underliner filled with tailings, which flowed through the hole. The evidence of fines migration through the hole, from the tailings to the underliner is discussed.