Excavation and Trenching
This week I would like to talk a little about Excavation and Trenching. Cave-ins due to Excavation and Trenching result in more than 100 fatalities each year. This is due to improperly protected walls of an excavated area, which can trap workers. Not only can a improperly protected wall cause injury or death, but also an improper barricade or flagged excavation area can put one in harm’s way.
There are a few ways to protect against injury from trench collapse. Protective systems that can be used include sloping, shoring, trench shield, and step trenching. Sloping is accomplished by cutting the banks back at an angle, with the proper angle, the soil would not slide toward the worker. Shoring would be a system of supports that brace the side walls of an excavation. Trench shield is a heavy metal box designed to be placed in the trench where workers would be inside the box and protected from a cave-in. Another system would be Step trenching. Step trenching is when you excavate the trench in a way that the trench would look like a large set of steps, working from the lowest area of the trench and working upward, and outward. Excavations four feet deep or more must also have at all time, sufficient means of emergency exit, this would be, a ladder (or some other means) within 25 feet of lateral travel from where work is being preformed.
Along with the proper wall protection for Excavation and Trenching, another very important safety system that should be installed, would be the use of proper barricading or flagging of the open trench. It is not unusual for a route that you were able to travel one day to be cut off by open trenching the next, or even the same day; this is why using the proper barricade or flagging is so important – this will allow workers and vehicle traffic to avoid the hazard area.
You can find more information on Excavation and Trenching in the OSHA Construction Standards, Subpart P 1926.650-.652
Len Kessner
Safety Director
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- Basic Hand Tool Safety
- Fire Extinguishers
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- Taking Shortcuts
2 Responses to “Excavation and Trenching”
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Install substantial stop logs or barricades when using mobile equipment on or near an (trenching)excavation, grade away from the excavation, and provide walkways or bridges with standard guardrails for employees or equipment to cross over excavations. If it is necessary to place or operate power shovels, derricks, trucks, materials or other heavy objects on a level above and adjacent to an excavation, the side of the excavation must be sheet-piled, shored, braced or sloped as necessary to resist the additional pressure resulting from such loads. Never excavate below the level of the base of the footing or retaining wall, except in hard rock, unless the wall is underpinned and appropriate precautions are taken to ensure the stability of adjacent walls. Materials used to support excavations should be maintained in good condition. Scaling, benching, barricading, rock bolting, wire meshing or other equally effective means of excavation support must meet accepted engineering requirements for all sides, slopes and faces of excavations. Excavations with conditions such as water, silty materials, loose boulders, erosion, deep frost action or earth fracture planes require that the slope of the earth adjacent to the excavation be lessened. For excavations in which employees may be exposed to unstable ground, qualified personnel using practices that are compatible with standards required by a registered architect, a registered professional engineer or other duly licensed or recognized authority will design support systems such as piling, cribbing, bracing and shoring that meet accepted engineering requirements to contain the walls.
Good summary of safety precautions. The one thing I’d add is that so many accidents are caused by operators cutting corners or rushing. Safety needs to be a priority every time.