Case History of an Exhumed Landfill Double Liner System

摘要

The opportunity of exhuming and evaluating various components of a double lined landfill system after 23 years of service is presented herein. The primary geomembrane (textured, 1.5 mm thick, HDPE) was evaluated and all eleven test properties were very close to the original properties and within current specification values. This was likewise the case for both extrusion and hot wedge seams. The geonet leak detection layer (4.4 mm thick, biplanar, HDPE) was in its original condition since no evidence of leachate was indicated. That said, the plastic cable ties holding the geonet sheets together were all broken in a brittle manner. The compacted clay liner beneath the secondary geomembrane was observed to have numerous long vertical cracks up to 15 mm wide throughout its thickness. The intact sections between the longer vertical cracks were striated with smaller cracks in all directions. While the clay's moisture content was 12%, the moisture content was likely higher during placement and subsequent shrinkage is the probable cause of the cracking.