An average of two workers is killed every month in the Trench collapses. Approximately, 300 Trench Collapse Accidents occur every year. Trench cave-ins are often deadly and occur more often in the underground utility industries. Other trench hazards may include the accumulation of toxic fumes in an enclosed space which can result in life threatening dangers and electrocution or explosions that are likely to occur when workers come into contact with unexpected electric cables or gas lines.
A trench collapse accident can lead to a number of injuries related to either falling or being crushed by the soil. Additionally, trench collapses can also cause other serious conditions such as Asphyxiation and suffocation.
Some of the common injuries associated with a trench collapse accident include:
- Asphyxiation (lack of oxygen);
- Poisoning (inhaling toxic fumes);
- Suffocation (weight of soil);
- Broken bones (falling or being crushed);
- Drowning (when water is involved);
- Burn injuries (from explosion or electrocution); and
- Death.
Cave-ins pose the greatest risk and are much more likely to result in worker fatalities. Other potential hazards include falls, falling objects that could lead to back, neck and head injuries. In addition to that, workers can also be injured by equipments, machinery or ladders that may fall onto workers leading to injuries.
Employers should ensure the safety of workers by:
- Testing for hazardous fumes;
- Providing safe access into and out of the area being excavated;
- Protecting employees from loose soil; and
- Other safety measures.
Any trench that exceeds 5 feet in depth must utilize a protective system and trench workers shall be protected from cave-ins by adequate protective systems, including:
- Sloping: cutting a trench wall at an angle
- Shoring: installing aluminum hydraulic or other supports to minimize soil movement and collapse, an
- Shielding: installing other supports, such as trench boxes, to prevent soil cave-ins.
If adequate protective systems are not installed, soil can shift and collapse on workers in a trench. One cubic yard of soil can have the weight of a car. Workers can suffocate and get crushed by the weight of the soil.
Ensure the protection of workers through Trench hazard training
Ensure that trench worker must have a clear understanding about the hazards involved and the necessary safety precautions such as:
- Never enter an unprotected trench.
- Keep the overload if any at least two feet from trench edges.
- The underground utilities must be located.
- Test for low oxygen, hazardous fumes, and toxic gases.
- Trenches shall be inspected at the start of each shift.
- Inspect trenches following a rainstorm.
- Never work under raised loads.
- Protective system shall be provided for trenches five feet deep or greater unless the excavation is made entirely in stable rock.
- A 20 feet deep trench or a greater one requires a protective system designed by a registered professional engineer or based on data supplied by a registered professional engineer.
- Any Excavated or other materials and equipment shall be placed at least two feet back from the edge of a trench.
- Provide a safe way to exit within 25 feet of workers in a trench.
- Trenches must be inspected daily by a competent person.
Essential safety aspects for trench work includes
- Complying required standards for trenching safety
- Having a written company policy
- Ensure the inspection of trenches by a Competent Person
- Wearing the appropriate Personal Protective Equipment (PPE)
- Continuous ventilation shall be ensured
- Ensure the use of Fall Protection Safeguards
- Use of Trench Shoring Systems
Complying required Standards for Trenching and Excavation Safety
As trench construction involves many complex factors, construction practices specifies detailed methods for protecting workers from cave-ins. Such standards cover requirements for sloping, shoring, and shielding as well as for installing and removing protective support systems. Workers and managers should ensure these standards are complied and reviewed regularly.
Companies should have a Detailed Policy
Construction companies should have a detailed policy that outlines safe trenching practices. This policy should specify the need for proper planning and supervision, frequent inspections to detect any change in soil conditions, and ensure adequate support for trenches. Having a written company policy will standardize safe practices for employees.
Ensure the inspection of trenches by a Competent Person
A Competent Person should be there to inspect trenches and identify potential hazards. Inspections must cover every aspect of excavation, safety and shoring equipment, and details such as type of soil, work in adjoining areas, the possibility of vibrations, and weather conditions. Competent person shall have the ability to identify existing and potential hazards in the surrounding area or dangerous working conditions and he shall be the authorized person to remove employees from dangerous areas and establish corrective measures if necessary.
Wearing the Appropriate Personal Protective Equipment (PPE)
PPE for Trenching and excavation includes hardhats, safety glasses, gloves, footwear, hearing protection, respirators and fall protection devices. Full-body safety harnesses equipped with a shock-absorbing lanyard attached to workers' backs and an anchor to a weight-bearing support shall be provided.
Continuous ventilation shall be ensured
Adequate ventilation shall be ensured in trenches to every occupied area within the confined space unless a low hazard atmosphere exists. Continuous ventilation can decrease the concentrations of airborne contaminants and gases below exposure limits.
Ensure the use of Fall Protection Safeguards
Ensure the use of standard railings or a safety harness and lanyard if a work environment extends six feet or more above the level below. Fall arrest posts should attach securely to the top of a rail panel or trench shield. In turn, four-to-six-foot-wide rails should be installed to support a 300 to 500 lb. load across any part of the fall protection system. Trench plates shall be provided to assure a safe surface crossing of trenches for foot traffic and vehicles.
Use of Trench Shoring Systems
Employers are responsible for providing shoring systems such as spaced sheeting, closed sheeting, slide rails, trench shields, and trench boxes in order to prevent the movement of soil and protect workers from accidents.,
Different techniques of shoring include spaced sheeting placing spaced timber shores, bracing, trench jacks, or other materials around the boundary of a proposed excavation, Horizontal planks that extend between the vertical materials to support the sheeting and Closed sheeting placing a wall of continuous solid plates along the entire length of the trench.
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