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Smaller Construction Firms: It May Be Time for an Onsite Non-Enforcement Consultation from OSHA
10 mai 2019
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Misunderstanding when or how to use a trench box can put workers in danger.
For some contractors, confusion exists around OSHA’s trench box requirements. Understanding when it’s appropriate to use a trench box and how to use one according to regulation is critical to keeping workers safe.
When trenches reach a depth of 5 feet or more, OSHA requires contractors to use a protective system. Protective systems are also required for trenches less than 5 feet deep if the soil might have the propensity to cave in when the trench is dug (such as with sand or mud). A competent person must evaluate the conditions and determine which type of protective system is needed in depths 5 feet or greater or in depths less than 5 feet when circumstances pose a cave-in hazard to workers.
RELATED: What Is a 'Competent Person'?
Trench boxes, also called trench shields or trench sheets, are one type of protective system. They aren’t designed to shore or prevent a trench wall from collapsing. Instead, they’re designed to protect workers from the pressure and weight of soil in the event of a cave-in. Unlike a shoring system, a trench box doesn’t provide any structural strength to the excavation itself.
Trench boxes are designed and built to withstand a lot of pressure from the earth that surrounds them. (One cubic yard of soil weighs 3,000 pounds, almost as much as a car.) Therefore, trench boxes are made from aluminum or steel, with sidewalls of varying thicknesses held apart by spreaders or other trench box panels of the same materials to achieve the desired width. The soil pressures and depth ratings on a trench box are determined by their designs.
OSHA has several regulations outlined in OSHA 29 CFR Part 1926.650-.652 Subpart P-Excavations that apply to the installation and use of trench boxes. Here are some of the most important points:
Designating a competent person and making sure that person is adequately trained is one of the most important steps to preventing trench injuries and fatalities. In addition, OSHA requires employers to train employees on the hazards they may be exposed to, how to protect themselves and what PPE is necessary to work safely.
If a competent person has any questions about the use of a trench box or the best protective system for a trench, the trench experts in United Rentals’ Trench Safety group can help.
Freelance writer Mary Lou Jay writes about business and technical developments in a variety of industries. She has been covering residential and commercial construction for more than 25 years.