Trench work and excavation are very common practices in construction operations, public utilities, mining and a variety of other industries. It literally lays the groundwork for most building and infrastructure projects, yet it can be one of the most dangerous tasks that you undertake on a daily basis.
Statistics show that between 50 and 100 workers die in trench collapses every year in North America and that excavation work has a fatality rate that is 112% higher than general construction tasks. Often, workers don’t perceive that trench operations are as dangerous as working from heights or with high voltage lines, and are more likely to take chances to save time. In many cases, the excuse used was that the worker was ‘just going to be down there for only a few minutes’, however collapses happen very quickly and they leave little time to react. Excavations are inherently unstable and it’s important to be prepared. In the vast majority of incidents reported, injuries or deaths occurred in trenches where no protective system was in place or where it was applied incorrectly. Sadly, there are a number of cases where a worker was killed and the equipment was on-site but not used.
Planning & Standards
Employers have a legal obligation to protect workers and the public when undertaking any kind of excavation work. This is why pre-planning, protective systems and evaluation by a competent person are so critical for all job sites where these activities are present.
- Employers should have an established Health & Safety committee or specifically assigned personnel that are responsible for the overall safety of their own workers, in addition to visiting contractors and the general public. It is critical that there is a complete understanding of all occupational health & safety laws pertaining to specific job safety, and that measures are put into place to maintain compliance. Emergency planning and water removal would be included in these procedures.
- Create and update a written set of formal safety policies related to trenching and excavation operations, and train all workers accordingly. This should also include emergency rescue, resuscitation and first aid procedures.
- Prior to starting projects, companies must determine if the proposed job meets or exceeds the scope and scale that would make it necessary to complete a Notice of Project with the Ministry of Labour. If the project is substantial enough, there may be a requirement for inspections, permits and specific documentation and procedures to be put into place. This would also include notifying utilities prior to digging.
- Daily trench and excavation inspections must be carried out by a ‘competent person’ who is qualified to do so. They must be familiar with safety and construction regulations and have the authority to intervene in cases where there are safety concerns. Additionally, trench work may require scaffolding, fall protection and lockout/tagout expertise, and these elements will also have to be accounted for.
Any time you dig, there will always be some natural risks that need to be addressed in order to keep everyone safe.
- One of the biggest hazards related to trenching and excavation is the risk of cave-ins. An unstable dig can easily collapse, either injuring or killing workers trapped inside. Most fatal cave-ins occur during smaller jobs of shorter duration where there is a perception that the hazards are not great enough to put safety measures into place. No one should ever enter a trench greater than 4 feet in depth without proper protection.
- Falls into open trenches or excavations are also a primary safety issue. Employers have a distinct responsibility to create buffers and barriers to keep this from happening.
- Accidental contact with overhead high voltage electrical equipment or underground utilities
- Confined space accidents including exposure to hazardous atmospheres
- Workers being hit with excavated material and other debris from overhead
- Workers being hit or crushed by falling overhead loads
- Falls while entering or exiting trenches
- Heavy equipment or vehicles falling into excavation sites through soil collapse or operator error
- Sudden flooding & water hazards
Equipment & Safety Techniques
Trenching & excavation are specific tasks that require specific safety precautions. Too often, safety measures are not used in order to save time, and it’s this breakdown in discipline that can have potentially devastating results.
Any excavation where there is a risk of a cave-in, must be approached with at least one of three primary safety techniques:
Sloping (or benching) involves cutting the walls of a trench back at a specific angle to add stability and help to avoid a collapse
Shoring systems work to physically support the walls of a trench. Timber or hydraulic systems are the most common and both must be designed by a qualified engineer.
Shield or trench boxes are lowered into the space to protect workers in the event of a collapse
- Keep excavated soil at least 2-3 feet from the edge of the dig , as the weight of the soil may trigger a collapse. Vibrations from heavy equipment may also contribute to this effect.
- The soil type and its condition are important in determining the potential for a collapse. It should be inspected daily by a qualified individual for cracks and fissures or any damage caused by water.
- No one should ever work alone in a trench. Most laws specify that there must always be at least one person working at ground level in case of an emergency.
- Workers must always have a safe means of entering and exiting a trench. This could include a ladder, steps, ramps or some other safe method.
- Heavy equipment should be kept at least one metre away from the upper edges of the trench or excavation
Here a few more tips that will help to contribute to everyone’s safety.
- All workers should be aware of their rights when it comes to excavation safety, and either raise their concerns or refuse to enter into potentially dangerous situations if proper precautions are not in-place
- Appropriate and approved personal protective equipment (PPE) must be worn by all workers involved in excavation and trench work. This would include a hard hat, safety footwear, hi-visibility clothing, eye and hearing protection as required and respiration equipment where hazardous atmospheres may exist.
- All safety and emergency equipment must be maintained close-by (and accessible) to the dig location. Having your equipment either far across your work site or locked-down in any way could cause potentially deadly delays in cases of a collapse.
- In the event of a collapse or if a worker becomes unconscious in a trench, a co-worker’s first instinct may be to rush down to help. Although the intentions may be well-meaning, this type of action could prove to be fatal to those responding. A structured (and fast) emergency response is always a safer bet for everyone involved. Local emergency services must also be notified immediately in these cases.
- Companies always have a direct responsibility to secure unattended dig sites when they are in proximity to the general public. These areas can be seen as very attractive play areas for children, and there have been many unfortunate accidents over the years. Adequate barriers and sign postings must be utilized at a minimum, with other measures such as overnight security supervision, being applied where required.
Trenching and excavation work is inherently dangerous, and it takes a concerted effort to keep both workers and the public safe from harm.