The article discusses how different types of soil affect the performance of landfill covers that help prevent water from seeping into the ground. The researchers studied soil properties at three sites in the US to understand how they impact cover design. In Colorado Springs, soil had uniform properties, while in Golden, soil was variable with layers of different textures. In Arlington, Oregon, soil stockpiles posed challenges for characterization. By analyzing soil samples from different depths and locations, the researchers found that soil type and variability play a crucial role in designing effective landfill covers.