A layer of peat was found while a trench was being dug as part of an excavation project.
Due to its low resistance to compression, peat is known to be harmful for foundations, which meant that the trench had to be made deeper.
Following instructions from engineering management, it was decided to remove the peat layer using machinery. The workers reached a depth of approximately 6 metres (20 feet) where clay was found.
Two workers entered the trench to measure the depth of the excavation while the construction manager supervised the work from above.
The wall collapsed, trapping them both underground. Both workers lost their lives.
Why did it happen?
Design standard was not applied - The trench was not shored, nor was there an incline that would allow people to enter it.
Flawed work permit - The trench measurement activity was not planned for in the work permit, therefore no workers should have entered the trench. There was no safe way for the workers to exit.
Process not implemented - Due to lack of safety supervision, the work conditions associated with the activity were not identified (unstable ground, falls, vibrations from nearby machinery, or piles of dirt near the edge), and unsafe behaviors were not stopped.
Weaknesses in the contractor management system - Aspects of the surroundings were not taken into consideration.
What did they learn?
Excavations, although a common and seemingly simple activity, are one of the main causes of fatal accidents. Therefore, it is very important that safety procedures are rigorously applied.
Assess and communicate risks so that workers perceive them appropriately and do not expose themselves to danger.
Ensure that there is always independent safety supervision in the field.
Manage contractors responsibly, ensuring their competence and compliance with safety requirements.
Ask yourself or your crew
What would be a safer way to perform this task if we found a layer of peat or other unstable materials on our site?
Have you ever had to work in an unsafe manner during trenching? What’s the worst that could have happened?
What are the hazards associated with your task today?
- How do you know that all hazards have been considered when planning the job?
- What should you do if something was missed?
What improvement can we make to the way we work so it becomes safer?
Add to homescreen
Select existing category:
Two workers entered a trench to measure the depth of the excavation while the construction manager supervised the work from above. The wall collapsed, trapping them both underground. Both workers lost their lives.