The first step is to find every hazard of the excavation work, looking at the physical environment, the equipment, materials and substances, the tasks and how they are done, and work design and management. Methods include inspecting the site and the work, talking to workers, manufacturers, suppliers and specialists, and reviewing records and incident reports. Hazards particular to excavation include: buried essential services carrying gas, water, sewage, telecommunications, electricity, chemicals, fuel or refrigerant; earth or rock falling or dislodging; falls between levels; falling objects; poorly placed spoil, plant or loads; instability of adjoining structures; previously disturbed ground; instability from people or plant near the edge; water or other liquid, including in-rush; hazardous manual tasks; hazardous chemicals in the soil; hazardous atmospheres, for example from methyl ethyl ketone solvent applied to PVC pipe joints in trenches with poor ventilation; hazardous noise and vibration; and overhead services such as powerlines or ground-mounted services such as transformers and gas and water meters.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.