Excavation and Trenching Safety

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by Rudi Nieuwoudt

Before jumping into this article, take a look at a few important facts about working in or around trenches and excavations:

  • Working in trenches and excavations is one of the most hazardous types of work.
  • As many as 400 workers have been killed yearly in trenches and excavations.
  • Several thousand more workers are seriously injured.
  • Most of the trenches and excavations in which workers are injured or killed are relatively shallow (1.5 m to 5m deep).
  • Many of the workers have not had excavation safety training.

The Weight of Soil

Weight of any soil depends on its bulk density i.e how tightly it is packed. usually bulk density varies from 1100kg to 1400kg for fine textured soil and 1400kg to 1700kg for coarse textured soil. It can be calculated by the formula given below:

Bulk Density = (Mass dried soil in Mega gram/total volume of soil in m3)

If bulk the bulk density of soil is 1.7, and volume of the soil is one cubic meter. then you can find the mass of the soil using above formula. i.e 1700 kg per cubic meter.

Similarly you can calculate for any soil with varying bulk density and volume.

Note: one mega gram is equal to 1000 kilo gram

The deaths and injuries result from suffocation, crushing, drowning, loss of circulation and objects rolling or falling into the trench or excavation.

Cave-ins are a simple matter of physics. Think about it: Before we excavate, all the physical forces of nature are in balance. There is equal pressure in all directions in the soil. But once we start excavating, we create a void — an empty space. The earth will want to “heal itself” — except in stable rock, which is extremely rare — by caving-in. The end result is that when trench walls cave in, and workers are not properly protected (by sloping, shoring or shielding), they will most likely be crushed. They don’t stand a chance. And there is a mistaken belief that workers have to be totally covered up to die. The reality is that workers die after being just partially buried. 

Why Is Safety so Important in Trenches and Excavations?

Stressing the importance of trench and excavation safety can never be underrated. No one wants a co-worker or an employee injured or killed on the job, so taking the proper precautions before performing this type of work is key. By establishing effective training and having the correct equipment on board, employees will feel a company values their safety. Potential employees will also want to work for a company that protects its workers. In addition to boosting morale, a dedication to safety helps better control direct and indirect costs, due to less accidents and lost time. Most importantly, maintaining a safe work environment is the law! Employers have a legal obligation to provide a safe workplace for all of their employees. Therefore, there’s no time to lose. Be sure your crews know the dangers of trench and excavation work and that they have the right tools to ensure they are safe on the job.

To protect workers from injuries and fatalities, preventive measures should be implemented when workers begin excavating. General safety measures to follow should cover the following:

  1. Inspect trenches daily before work begins. Don’t go near an unprotected trench.
  2. Check weather conditions before work, be mindful of rain and storms.
  3. Keep heavy equipment away from trench edges.
  4. Be mindful of the location of utilities underground.
  5. Always wear proper protective equipment.
  6. Don’t work beneath raised loads.
  7. Conduct atmosphere tests. If low oxygen and toxic gases were detected, workers must not enter the trench.
  8. Protective systems like benching, sloping, shoring and shielding must be created.
  9. Planning and implementation of safety measures must be done by a competent person.
  10. Use a checklist to perform regular self inspections – download free excavation safety checklists here.