Transit times through compacted clay liners

Transit time, or time taken by waste liquid to move through the thickness of the liner, is a short-term performance parameter which can be used to determine the necessary liner thickness. In order to predict the transit time for a given liner configuration, one should be able to analyze the transient flow situation in which a wetting front of waste liquid moves through the initially unsaturated compacted clay mass. The analysis is further complicated by the fact that the liquid movement takes place along preferred paths and not uniformly throughout the entire cross-section. This paper reviews the current methodology for simulating the above flow condition and how they may be used for transit time prediction.