The 2000 R.M. Hardy Lecture: Full-scale hydraulic performance of soil-bentonite and compacted clay liners

The results of laboratory and in situ permeability tests can be used to predict the total leakage rate of a soil-bentonite or clay liner. This prediction, however, ignores the large influence that minor defects may have on the total leakage. In Quebec, hundreds of municipal wastewater ponds have been filled with water to measure their total leakage rate before approval. The design criteria and the equations to be used for the full-scale performance test are briefly reviewed with their capacities to detect hydraulic deficiencies. Several case histories are presented to illustrate various problems: excessive leakage of a stable soil-bentonite mix, washing of bentonite in a soil-bentonite mix, internal erosion of a natural clay liner through an inadequate sand filter, and effects of freezing on the total leakage of a clay liner.