When a trench runs beside an old service line, spoil should go on the opposite side so previously weakened ground is not overloaded. Where fences, buildings or trees force spoil close to a trench and its weight could overload the sides, the ground support should be strengthened at those spots and toe boards or similar barriers may be needed to stop material falling in. Loose soils settle at characteristic slopes, sometimes called the angle of repose, but the Code warns that basing the safe slope of an excavation on that angle is poor practice even where the two happen to be similar.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.