Comment by wiradikusuma

"Excavation cave-ins cause serious and often fatal injuries to workers in the United States. An analysis by the National Institute for Occupational Safety and Health (NIOSH) of workers' compensation claims for 1976 to 1981 in the Supplementary Data System of the Bureau of Labor Statistics suggests that excavation cave-ins caused about 1,000 work-related injuries each year. Of these, about 140 result in permanent disability and 75 in death. Thus, this type of incident is a major cause of deaths associated with work in excavations and accounts for nearly 1% of all annual work-related deaths in the nation."

http://www.cdc.gov/niosh/docs/85-110/