A database is described that contains results of laboratory measurements of hydraulic conductivity and associated soil properties performed on compacted clay samples from two Belgian landfills. The measurements were conducted on a base liner of one landfill and a capping liner of another. The data were used to evaluate hydraulic conductivity and compaction conditions and to compare the results with quality control testing and acceptance standards of the clay prior to construction. The variability of the test results is evaluated and checked against the acceptance standards. The base liner properties are well within the acceptable standards. However due to difficult compaction conditions on the side slopes, some samples of the capping liner failed the acceptance criteria. Through an evaluation procedure which takes into account the variability and probability of exceeding of the acceptance standards, the conductivity performance of both liners is accepted.
Compacted clay liners are widely used as hydraulic barriers in waste containment facilities. To be effective, a compacted soil liner should have low hydraulic conductivity, which in many cases is prescribed in standards or project specifications. (Rowe 1997; Areias et al. 1998). Evaluation of such liners, both from a design point of view as well as in the testing of the actual liner, is of great importance as processes involving ground water flow and contaminant transport are relatively slow and the effectiveness of the liners in situ cannot be measured immediately. Results have shown that a more rigid approach to the design process and quality control is necessary to be able to compare the actual performance of the liner based on test results with the original design criteria. Results are used statistically to determine whether or not the performance of the liners meets the design specification by taking into account the variability of the results.
