Figure 1 Trench Safety
I’ve heard a safety professional describe a trench as a grave without the ends. They were referring to the fact that unless the trench is shaped and shored (using wood etc to support the face of the trench walls) correctly then it can collapse on those working at the bottom of the trench. In the US alone, this accounts for 5000 injuries and 100 fatalities per year. Similarly, in the UK trench safety injuries are ongoing.
In New Zealand the Department of Labour has provided an excellent code on best practices for excavation and trenching. Please read it and apply it to your business. The following video shows an inspector stopping work until a trench can be made safe; watch and apply trench safety techniques to your business.