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Excavating or trenching work can be highly dangerous and may lead to death or severe injuries if not carried out safely. The hazards presented by this work include burial, falls from height or being struck by objects falling into the excavation, drowning, striking underground services (e.g. gas, electricity and water), as well as asphyxiation or poisoning caused by fumes entering the excavation.
To reduce the risks involved with excavation work, adequate precautions should be taken to include:
To reduce the risks involved with excavation work, adequate precautions should be taken to include:
Checking for underground services before work commences
Shoring of the excavation sides or ensuring they are at a suitable angle to prevent the sides collapsing or material falling onto workers in the excavation or trench (essential at 1.5 meters (5ft) or deeper)
Measures to prevent persons, materials or objects falling into the excavation or trench or the inrush of water into the excavation / trench
Maintaining an atmosphere fit for breathing
Measures to enable workers to leave the excavation or trench safely
Avoiding vehicular traffic near the excavations or trenches or ensuring it is kept to a minimum
Before beginning an excavation:
Before beginning an excavation:
All work should be planned and the method of excavation and the appropriate type of support identified
The stability of the ground should be verified by a competent person
A competent person should check that the excavation will not affect adjoining buildings, structures or roadways
The position of all the public utilities such as underground sewers, gas pipes, water pipes and electrical conductors should be verified
If applicable, the gas, water, electrical and other public utilities should be disconnected or rerouted
If underground pipes, cable conductors, etc., cannot be rerouted or disconnected, they should be fenced, supported and adequately marked or otherwise protected
If necessary, land should be cleared of trees, boulders and other obstructions
An analysis of possible contamination of the land by harmful chemicals or gases, or by any hazardous waste material such as asbestos should be made
The collapse of the sides can result from:
The collapse of the sides can result from:
An angle of inclination greater than the natural angle of slope
An increase in weight due to overloads in the areas bordering the ridges of the slope
Infiltration of water
Vibrations due to machinery or vehicles
Existence of overloads in neighboring areas
To avoid the collapse preventive measures should be taken:
To avoid the collapse preventive measures should be taken:
Decrease the slope of the sides of the excavation
Prevent water from infiltrating (drainage systems)
Install blankets to protect the embankment structures (mortar / concrete)
Avoid vibration and overloads
Regularly inspect the slope and the surrounding areas
Shoring:
Shoring:
The sides of the excavation or trench should be supported by timbering or other suitable means or sloped and battered back to a safe angle of repose to prevent a collapse. The type of support necessary and angle of repose will depend upon the type of excavation, the nature of the ground and the groundwater conditions.
ATTENTION: Shoring or other means of supporting excavations and trenches should be conducted under the supervision of a competent person. The removal of any supporting mechanisms should also be conducted under the supervision of a competent person.
Fall Risk:
Fall Risk:
To avoid the risk of workers falling into the excavation or trench, suitable barriers (double guard rails) should be erected to prevent falls.
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