For non-vehicular uses such as embankment stabilization, the maximum slope is determined by the angle of repose of the bedding sand, typically around 35 to 38 degrees. For vehicular traffic, the highest slope in use is 18% (about 10 degrees) in a street in Colman, California. Special consideration is given to the drainage of the bedding sand at the bottom of the slope. Contact ICPI for details and guidance. Intermittent concrete header beams are generally not required.