OSHA revised the excavations standard in 1989, with focus on the existing standard to simplify many of the existing provisions, add and clarify definitions, eliminate duplicate provisions and ambiguous language, and give employers added flexibility in providing protection for employees.
In addition, the standard provides several new appendices. Appendix A to 1926.652 provides a consistent method of soil classification. Appendix B to 1926.652 provides sloping and benching requirements. Other appendixes (appendices C-F) provide pictorial examples of shoring and shielding devices, timber tables, hydraulic shoring tables, and selection charts that provide a graphic summary of the requirements contained in the standard.
For more information on the details of proper installation, please refer to the OSHA standard on excavation (29 CFR 1926 Subpart P, which includes 650-652 and appendices A-F).
The OSHA standard applies to all open excavations made in the earth's surface, which includes trenches. According to the OSHA construction safety and health standards, a trench is referred to as a narrow excavation made below the surface of the ground in which the depth is greater than the width (the width not exceeding 15 feet or 4.5 meters).
An excavation is any man-made cut, cavity, trench or depression in the earth's surface formed by earth removal. This can include excavations for anything, from cellars to highways.
The standard does not apply to house foundation/basement excavations (including those that become trenches by definition when formwork, foundations or walls are constructed) when all of the following conditions are present:
The standard provides several options for designing trench protection measures. Under certain conditions, the design of the trench protection measures must be prepared by a registered professional engineer.
Proper selection and installation of trench protection measures are very important. To comply with the standard, the employer must have a competent person:
“one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.”
This competent person has critical inspection responsibilities regarding excavations. This person must inspect every excavation and protective system under his or her care daily, including areas adjacent to any excavation. Additional inspections must be conducted before starting work and as needed through a shift, for example, when any hazard-increasing occurrence (such as a rainstorm) takes place. When the competent person finds any evidence of a situation that could result in a cave-in, protective system failure or any other hazardous condition, employees are to be immediately removed from the danger area until the problem is fixed.
The items below discuss more trenching and excavation activities where a competent person is necessary:
Many companies have established a written policy that outlines specific safe trenching practices in detail. Such a policy should ensure adequate support for the trench and frequent inspections of the excavation site to detect any change in the soil conditions.
Field and office personnel should become familiar with the company policies and guidelines outlined in the company safety program. The program may be put into writing to communicate the company’s position regarding jobsite safety. An example of a company safety and health program in action is a written policy that ensures all employees in all excavations will be protected from cave-ins. When this type of policy is enforced, all employees understand their responsibilities and that helps to avoid unsafe practices.
On January 28, 2003, two Hispanic construction laborers [15 and 16-year-old brothers] died when the trench they were working in experienced a cave-in. The victims were members of a crew installing conduit in an eight-foot-deep by two-foot-wide trench.
When work started, the jobsite foreman instructed the crew leader to operate a backhoe to dig the trench. The foreman then left the site to check on another job. After approximately an hour, the crew leader grounded the bucket, turned the machine off and walked to the company trailer to check blueprints.
As he was looking at the blueprints, he heard loud voices outside the trailer from the direction of the ditch. As he exited the trailer, he was informed by one of the workers that the trench had collapsed and that the two employees had been covered up.
The emergency medical squad (EMS) was summoned and responded within minutes.
Coworkers had uncovered the victims and removed them from the trench as the rescue squad arrived. The victims could not be revived and the county coroner was summoned to the scene where he pronounced the victims dead.
NIOSH investigators concluded that, to help prevent similar occurrences, employers should:
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