This webinar will provide insight into the interface strengths that should be used on the base and sideslope of a geosynthetic lined slope and the accompanying factors of safety. Numerical analyses will be presented that show the residual, large displacement, or post-peak interface strengths that should be used on the sideslope depending on the length and inclination (3H:1V to 6H:1V) of the sideslope. Finally the impact of liquid and buildup of fines on the textured geomembrane/nonwoven geotextile and drainage geocomposite interfaces will be discussed using the results of direct shear and ring shear tests on these interfaces. 1.0 PDH