Evaluation of Atactic Polypropylene (APP) geomembranes used as liners for salt ponds

Abstract

This study focused on evaluating the longevity of Atactic Polypropylene (APP) used as a geomembrane (GM) to line ponds that collect runoff water from salt handling facilities. Samples of APP were exhumed from the ponds that have been in service for 6-, 25-, and 44-years and evaluated in the laboratory. Tests were conducted to analyze the surface cracks and textures, tensile properties, puncture resistance, and ability to hold water (permeability). Control tests were conducted with virgin APP GM. Results were compared based on the difference in the age of the APP, location of where the APP samples were obtained within the side slope of the pond (i.e., submerged, and above water level), and orientation of the side slope in relation to the sun (e.g., east, west, north, or south). Based on the field observations and laboratory evaluations, it was determined that exposure to sunlight accelerates the degradation more so than the chemical degradation that occurs due to the salt content within the pond water. The samples exhumed from the north slope (south-facing) had more severe degradation due to high solar radiation energy deposition.