A significant number of deaths and injuries in sewer and watermain work are directly related to trenching. Trenching fatalities are mainly caused by cave-ins. Death occurs by suffocation or crushing when a worker is buried by falling soil. Over half of all powerline contacts involve buried cable. Before excavating, the gas, electrical, and other services in the area must be accurately located and marked. If the service poses a hazard, it must be shut off and disconnected. Read more here.
IHSA (1991): Trenching Safety - Introduction to Trenching Hazards. Mississauga: Infrastructure Health & Safety Association URL [Accessed: 16.05.2019]