ABSTRACT
The evaluation of the suitability of a clay liner has often focused on the hydraulic conductivity. Diffusion involves the movement of contaminants from points of high chemical concentration to points of lower chemical concentration. Advection dominates over diffusion for Darcy velocities greater than 0.02 m/annum in the case considered here. Both advection and diffusion play a very important role for intermediate velocities. The Confederation Road landfill near Sarnia, Ontario is one of the best-documented case histories where the migration of contaminants. The process of collecting and treating leachate involves the removal of mass from the landfill and hence a decrease in the amount of contaminant that is available for transport through the liner and into the general groundwater system. An important practical consequence of the foregoing is that its not necessarily conservative to design only for the maximum and minimum expected velocities in the aquifer.
