Leakage rate calculations for both low permeability soil liners and co
mposite liners using flexible membrane liners (FMLs) overlying low-per
meability soil are developed Latin-Hypercube simulations with uncertai
nty assigned to the soil liner hydraulic conductivity value and the sp
atial frequency of FML holes are used to examine: the variability in t
he liner leakage rates. The low-permeability soil hydraulic conductivi
ty is the parameter with the greatest effect-on landfill liner leakage
s rates. Composite liners have a significant impact on reducing leakag
e-rates through the landfill liner.