Construction projects involving excavation and trenching are the most hazardous workplace activities. An excavation is described as any man-made cut, cavity, trench, or depression which is formed by earth removal. The term “trench” is specific to underground excavations which can be deeper as opposed to wide, being no wider than 15 feet. The fatality rate for all those types of excavation tasks are 112% greater than that of general industry (U.S. Occupational Safety and Health Administration). Given this advanced level of danger, it’s important that health concerns and controls be applied out all times understanding that extreme caution and patience be exercised when doing work in and around pits and excavations.
Types of Excavation Risk
Cave-ins pose the highest risk and are also the most likely sort of excavation-related incident to lead to fatalities. Other potential hazards related to excavation include:
• Falls into trenches or excavations
• Tripping over equipment, debris and spoil
• Excavated material or any other objects falling on workers
• Exposure to underground services or overhead lines
• Mishandled or poorly placed materials
• Difficulty breathing caused by noxious gases or not enough oxygen
• Toxic, irritating, or explosive gases
• Vehicles and mobile equipment
Mitigating the Risk
The two basic ways of protecting workers against cave-ins are sloping and temporary protective structures.
Sloping involves restricting the trench wall with an angle which is inclined outside the work area from the excavation. The appropriate angle in the slope is dependent upon the soil conditions to begin of excavation.
Temporary protective structures are made to provide protection from cave-ins, collapse, sliding or rolling materials. Examples of temporary protective structures include shoring, trench boxes, pre-fabricated systems, hydraulic systems, and engineering systems.
Shoring is often a system that props up the sides or walls and normally necessitates use of aluminum, steel, or wood panels which can be supported by screws or hydraulic jacks. Shoring ought to be done in conjunction with the progression from the excavation. If there is any delay between digging and shoring, no workers should go into the unprotected trench. Trench Boxes in many cases are used in open areas which are away from utilities, roadways, and foundations. Trench boxes can often protect workers within the of cave-ins, but are not an alternative to shoring. If the trench or excavation walls are created from rock, rock bolts or wire mesh can often offer additional support.
Excavation Safety Tips:
• Know the location associated with a underground utility lines
• Wear proper PPE – including protective hardhat, eyewear and footwear
• Keep heavy equipment from trench edges
• Test for low oxygen and toxic gases.
• Inspect trenches at the outset of each shift or if there is significant rainfall
• Place barriers over the outside perimeter and safety signs at key locations
• Consider seeing a professional engineer with regards to the design and installing on the shoring
• Establish a safe methods of access and egress
• Know the location of water sources and what are the drainage patterns will be
• Develop an urgent situation response plan you need to include provisions for extreme weather, evacuation routes, and communication plans
What NOT to do:
• Do not enter an unprotected trench deeper than 4 feet
• Do not start digging before locating and de-energizing the buried services
• Do not enter a trench before testing the air
• Do not place anything within 1 metre through the trench’s edge
• Do not depend on natural freezing to do something as a way of soil stabilization
It’s donrrrt forget to remember that collapses may occur without warning, regardless on the depth. In fact, almost all fatalities occurs at minimal depths when workers are not able to appreciate the potential for loss involved. All excavation projects present serious safety risks, but injuries and fatalities presented by collapses are preventable with the right planning and security measures.