Observations of Field Condition of an Exposed Geosynthetic Liner System

Abstract

Preliminary field observations during the removal of a composite geosynthetic liner system that had been exposed for more than a decade are presented. The liner system was installed at a cell in a Subtitle D municipal solid waste landfill in San Luis Obispo, California (USA). The liner system consisted of (from top to bottom) a 1.5 mm-thick black HDPE geomembrane, a needle-punched geosynthetic clay liner (GCL), and a compacted subgrade. The liner system was not covered at any time since construction. The sides of the cell were relatively steep at 2H:1V slopes. Initially, the geomembrane was removed followed by removal of the geosynthetic clay liner. The geosynthetic clay liner panels were observed to be separated at multiple locations with gaps up to 220 mm wide and up to approximately 17 m long. The GCL also was relatively dry with granular consistency. In addition, a significant amount of bentonite that migrated from the GCL had accumulated between the GCL and the geomembrane at the toe of the slope.