In order to increase safety awareness in the trenching industry, the Occupational Safety and Health Administration (OSHA) has enacted a National Emphasis Program for trenching operations. However, it would seem that even the most common hazards of the job still tend to be disregarded. Many employers continue to receive citations for safety violations; and since 2003, there have been 200 deaths resulting from trench-related incidents, according to OSHA.
Fortunately, knowing a few basics about trenches can help people come up with the best means of protecting personnel in these worksites. From posting trench signs to comprehensive protective systems, taking the time to understand/review trenches goes a long way in developing the proper safety practices and standards for working in them.
Knowing the Lay of the Trench
A lot of the dangers encountered in trenches are due to its unstable nature as well as the work environment. One cubic yard of compacted dirt, for instance, can weigh as much as 2,500 pounds, or even more. To illustrate: that amount of dirt would fit into a 3” x 3” x 3” container.
Then there are different kinds of dirt, which naturally have different characteristics. OSHA’s classification of soils includes three different types. Clay, and soil mixtures with clay (such as sandy clay and clay loam), are classified as Type A soils, as well as cemented soil types such as hardpan and caliche.
Type B soils are soils that resemble crushed rock, such as angular gravel, sandy loam, silt loam, and silt. Type C soils include granular soils and wet soils, among which is sand, loamy sand and gravel. Soils in this category are considered the most unstable types of dirt.
The potential for cave-ins is perhaps the greatest risk to workers employed in trenches. There are other potential hazards, however, which include drowning, toxic fumes, asphyxiation, or electrocution by underground wires.
Because of these hazards, OSHA requires that these sites implement protective systems for those who are involved in the work process. Having the proper trench signs installed is a simple yet efficient means of informing people to always be alert.
The area must also be inspected by a qualified individual; someone who has the authority to immediately eliminate hazards, and who is therefore trained in soil analysis, trench protective systems and safety requirements. Inspections should be performed before the work begins, as well as prior to each shift, and after any rain storms or other events that may have compromised the stability of the area (such as whenever machinery has been driven too close to the trench’s edge.)
Another cause for cave-ins are the materials excavated from the site – or spoils – that have been placed too close to the edge of the trench. There should be at least 2 feet distance between the edge and where the spoils and equipment are placed. In cases where there is no adequate space, the items should be moved somewhere else, at least temporarily.
A retaining device (such as a trench box) should be used whenever possible, to prevent debris and other objects from falling back into the excavation. The trench box should be located above the rim of the trench in order to further ensure this.
Entrance and Exit.
For all trench sites that are 4 feet deep or more, it is required that ladders, stairways or ramps be installed, to avoid injuries to the employees entering or leaving the area. These must be properly designed by knowledgeable individuals, and workers should have access to an exit route within 25 feet of their work area.
Trenches are, by nature, dangerous workplaces that pose various threats to worker safety and well-being. However, a few simple precautions such as careful worksite survey and using the correct equipment such as trench signs will go a long way in preventing fatal accidents and costly damages.
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