- 488 workers have died in trenching or excavation cave-ins over the past 9 years—an average of 54 fatalities per year
- 64% of fatalities in trenches occurred at depths of less than 10 feet
- 68% of those fatalities occurred in companies with fewer than 50 workers
- 46% of the deaths occurred in small companies with 10 or fewer workers
- Lack of a protective system is the leading cause of trench-related fatalities
- Most incidents involve excavation work related to water, sewer, pipeline, and communications and power-line construction
The unfortunate and unnecessary death of an Edmonton excavation worker in a completely preventable trench collapse on April 30 has once again highlighted the need for better excavation safety training. The worker was trying to access the water main located in a 2 to 3 meter (6.5 to 10 feet) trench located on a residential construction in-fill project burying him alive under more than a meter of clay. Just in case you’re wondering one cubic meter of soil weighs between 1.2 and 1.7 metric tonnes, or between 1,200 and 1,700 kilograms. That equates to roughly 2,645 and 3,747 pounds, or between 2.6 tons and 3.7 tons, per cubic meter. This amount of weight will crush and suffocate you within minutes. OH&S is currently investigating the incident.
Regardless of whether you are working on a residential construction site, or installing a high pressure pipeline in the middle of nowhere, there are certain regulations that govern how you must complete the excavation. These regulations are in place to protect both workers and the general public from the tragedy of a trench collapse.
There is no reliable warning when a trench is going to fail
In Alberta, ALL Employers and their employees are governed by the Occupational Health and Safety Code. The OH&S Code includes a specific section, called Part 32 Excavating and Tunneling, which covers everything from disturbing the ground, soil classifications, buried facilities to methods of protection and safety, that are required by law while excavating.
In Part 32 subsection 450(1) “Methods of Protection” the regulation states; Before a worker begins working in an excavation that is more than 1.5 meters (4.9 feet) deep and closer to the wall or bank than the depth of the excavation, an employer MUST ensure that the worker is protected from cave-ins or sliding or rolling materials by
- cutting back the walls of the excavation to reduce the height of the remaining vertical walls, if any, to no more than 1.5 meters for hard and compact soil and likely to crack or crumble soil
- installing temporary protective structures, or
- using a combination of the methods in clauses (1) and (2)
In Part 32 subsection 456(1) “Temporary Structures” the regulation states; An employer MUST ensure that temporary protective structures in an excavation;
- 3 meters (9.8 feet) deep or less are of sufficient strength to prevent the walls of the excavation from caving in or otherwise moving into the excavation, and
- more than 3 meters (9.8 feet) deep are designed, constructed and installed in accordance with the specifications of a professional engineer.
It is evident to me, the appropriate safety precautions stipulated under OH&S regulations were not implemented, adhered to, understood or possibly even completely neglected. The facts state the trench was 2 to 3 meters in depth, meaning that the employer had the responsibility to ensure appropriate methods of protection were in place given the trench was over the 1.5 meter safe threshold. If the trench had the appropriate methods of protection in place like cutting back or sloping of the trench walls, combined with temporary protective structures this tragedy would have been averted. Unfortunately, the hazards associated with trench work and excavation are recognized and preventable, yet injuries and fatalities associated with these hazards continue to occur.
Workers who dig or excavate trenches are at risk of death if they enter an unprotected trench and the walls collapse. However, hazards associated with trench work and excavation are well defined and preventable. There is no reliable warning when a trench is going to fails. The walls can collapse suddenly, and workers will not have time to move out of the way. Workers should NEVER enter a trench that does not have a protective system in place designed and installed by a competent person. Factors such as type of soil, water content of soil, environmental conditions, proximity to previously back-filled excavations, weight of heavy equipment or tools, and vibrations from machines and motor vehicles can greatly affect soil stability.
Workers are at risk of death from cave-ins during trenching and excavation activities. It is always recommended to know the regulations to properly implement engineering controls, protective equipment, and safe work practices to minimize hazards for workers before the job even begins.
Don’t Dig Your Own Grave !
Know your responsibilities as an employer. Know your rights as employee. Know the excavation and trenching regulations and best practices but most importantly get the proper Ground Disturbance and Safe Excavation training.