Eliminate hazards and control risks by implementing precautions in excavations and trenches.
The speed of an excavation collapse increases the risk associated with this type of work. The consequences are significant as the falling earth can bury or crush any person in its path resulting in death by suffocation or internal crush injuries.
All work involving excavations must comply with the requirements of the Occupational Health and Safety Act, Act 85 of 1993 and all relevant regulations, including the Construction Regulations 2014 (CR14) and the General Safety Regulations 2003 (GSR 2003).
Below are guidelines that have been put in place to assist with the safety of employees while working with excavations:
What is excavation work?
Excavation work generally means work involving the removal of soil or rock from a site to form an open face, hole or cavity, using tools, machinery or explosives.
Excavation work can occur anywhere, including:
on construction sites
on business premises
in public areas.
Excavation work includes:
open excavations
potholing
pit excavations
trenches and retaining walls
shafts and drives
What is the Difference Between Trenching and Excavation?
The scope and application of excavation standards states that excavations include trenches which means that a trench is a type of excavation. Moreover, a trench is further defined as a narrow excavation in relation to its length, and it is generally greater in depth than width. The main difference is that “excavation” is the umbrella term that encompasses any man-made cut in an earth surface, including trenches. While a trench can be called a trench excavation and all trenches are excavations, not all excavations are made up of trenches only.
Why is Excavation and Trench Safety Important?
Excavation and trenching are amongst the most dangerous operations in the construction industry. Dangers can include cave-ins, falling loads, hazardous atmospheres, and hazards from using heavy equipment. Regular pre-work inspections can reduce hazards and serious risk of injury. Safety inspections should check for the type of excavation being conducted, support and warning systems in place, access areas, weather conditions, heavy equipment, and PPE.
What are the Hazards in Excavation?
“The making of any man-made cavity, trench, pit or depression formed by cutting, digging or scooping.” according to the CR14 definition, excavations involve many hazards. Here are some of the dangers brought by excavations:
The collapse of the sides of the excavation.
Materials falling onto people
Falls, either people or vehicles.
Nearby structures collapsing into the excavation.
Electrocution, explosion, gas leak, or flooding, caused by damage to underground services.
What are the Safety Measures for Excavation?
One of the main reason why trenches collapse is that they are not properly protected. Protective systems such as sloping the ground, benching the ground, shoring the trench with supports such as planking or hydraulic jacks, and shielding the trench using a trench box should be properly implemented at all times. Other excavation safety measures include:
Collapsing should be avoided by supporting the sides by either battering them or supporting them with sheets.
Materials from the excavation should be stored at a safe distance from the excavation, this will help reduce the risk of them falling onto people.
Adding barriers to excavation is an essential precaution to avoid people falling into the excavation.
It is safer if vehicles are kept completely out of the excavation area, but if required the use of barriers and stop-blocks should help mitigate that danger.
Cable, pipe, and service plans should be used to ensure that underground services are known so they can be marked on the ground or, ideally, the area avoided entirely.
Around the areas where there are underground services, mechanical equipment should be avoided and instead use spades and/or shovels.
Picks and forks should be avoided as they are more likely to pierce cables and pipes.
Flooding can be avoided by ensuring that there is appropriate pumping equipment so that any water that seeps into the excavation can be easily pumped out to a safe area.
Prescribed Excavation Protection
Supervision:
All excavation work must be carried out under the supervision of an appointed competent person.
Stability:
Evaluate the stability of the ground before excavation work begins.
May not require or permit any person to work in an excavation which has not been
adequately shored or braced, unless:
the sides of the excavation are sloped to at least the maximum angle of
repose measured relative to the horizontal plane; or
such an excavation is in stable material and permission has been given in writing by the appointed competent person
Shoring or bracing contemplated above
Is designed and constructed in a manner that renders it strong enough to support the sides of the excavation must ensure that no load, material, plant or equipment is placed or moved near the edge of any excavation
(e) must ensure steps are taken to ensure the stability of any building, structure or road and the safety of persons where the excavation is close to such.
Access:
Must provide convenient and safe means of access, and such access may not be further than six meters from the point where any worker within the excavation is working.
Services:
Must before the commencement of excavation work that may affect any service, ensure the circumstances are safe for all persons involved.
Inspections:
Inspect every excavation, including all bracing and shoring, -
daily, prior to the commencement of each shift;
after every blasting operation;
after an unexpected fall of ground;
after damage to supports; and
after rain, and those results must be recorded in a register kept on site
Barricading:
Must make sure every excavation which is accessible to the public or which is adjacent
to public roads or thoroughfares to be-
adequately protected by a barrier or fence of at least one metre in height and as close to the excavation as is practicable; and
provided with warning illuminates or any other clearly visible boundary indicators at night or when visibility is poor.
Confined Spaces:
Must ensure that all precautionary measures stipulated for confined spaces asdetermined in the General Safety Regulations, 2003, are complied with by any person entering any excavation.
Warning signs:
Must place warning signs next to an excavation within which or where persons are working or carrying out inspections or tests.
Who is a Competent Person in Excavation Safety?
A competent person in excavation safety is an individual, designated by the employer, who has the authorization to take immediate corrective actions to eliminate excavation-related hazards that are dangerous to workers. Moreover, an excavation competent person should be able to classify soil, inspect protective systems, design structural ramps, monitor water removal equipment, and perform site inspections.
Excavation Safety Toolbox Talk Topics
Another way to help reinforce excavation safety is by conducting toolbox talks regularly. Listed below are sample ideas of relevant excavation safety topics you can talk about with your team:
Safe Excavation Access and Egress
Preventing Displacement of Ramps and Runways
Safety Tips for Sloped and Benched Excavations
Detecting Signs of Hazardous Atmosphere
Precautions for Exposure to Vehicular Traffic
Safety Measures for Exposure to Falling Loads
Protection from Water Accumulation-related Hazards
Accepted Engineering Practices for Specific Excavation Sites
Basics of Emergency Rescue Equipment
How is Excavation Done Safely?
To protect workers from injuries and fatalities, preventive measures should be implemented when workers begin excavating. According to best practice, general safety measures to follow should cover the following:
Inspect trenches daily before work begins. Don’t go near an unprotected trench.
Check weather conditions before work, be mindful of rain and storms.
Keep heavy equipment away from trench edges.
Be mindful of the location of utilities underground.
Always wear proper protective equipment.
Don’t work beneath raised loads.
Conduct atmosphere tests. If low oxygen and toxic gases were detected, workers must not enter the trench.
Protective systems like benching, sloping, shoring and shielding must be created.
Planning and implementation of safety measures must be done by a competent person.
Use a checklist to perform regular self-inspections.
View Construction Regulations.