Before excavation work begins, the PCBU has extra duties under WHS Regulation 305 to manage four risks: a person falling into the excavation; a person being trapped when the excavation collapses; a person working in the excavation being struck by something that falls; and exposure of a person in the excavation to an airborne contaminant. In doing so the PCBU must take account of all relevant matters, including what the excavation is, what the work involves and the range of possible methods for doing it, and, where relevant, how people will get into and out of the excavation.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.