Forensic analysis of excessive leakage from lagoons lined with a composite GCL

A forensic investigation of excessive leakage from two lagoons is described. The lagoons were lined with a composite geosynthetic clay liner (GCL) consisting of a thin geomembrane laminated to one side of a conventional GCL (i.e. granular bentonite encased between two geotextiles). The GCL was installed with the geomembrane in contact with the subgrade. Layers of sand (150 mm) and gravel (300 mm) were placed on top of the GCL to protect it from wave action. Field-scale leakage rates were estimated by monitoring water levels with a graduated rod and by measuring the pressure at the bottom of each lagoon using pressure transducers. In addition, leakage through the GCL panels was measured in situ with sealed double-ring infiltrometers and in the laboratory using flexible-wall permeameters. Leakage rates for the overlaps were measured in the laboratory with flow box tests on GCL specimens from the lagoons. Tests were also conducted to assess the swelling capacity and ionic composition of the exchange complex ...