The Safety Blog - I am Wright.com

The standard requires the employer to provide support systems such as shoring, bracing, or underpinning to ensure the stability of adjacent structures such as buildings, wells, sidewalks or pavements.

The standard prohibits excavation below the level of the base or footing of any foundation or retaining wall unless: (1) a support system such as underpinning is provided, (2) the excavation is in stable rock, or (3) a registered professional engineer determines that the structure is sufficiently removed from the excavation and that excavation will not pose a hazard to employees.

Excavations under sidewalks and pavements are also prohibited unless an appropriately designed support system is provided or another effective method is used.

In addition, the standard permits excavation of two feet or less below the bottom of the members of a support or shield system of a trench if: (1) the system is designed to resist the forces calculated for the full depth of the trench, and (2) there are not indications, while the trench is open, of a possible cave–in below the bottom of the support system. Also, the installation of support systems must be closely coordinated with the excavation of trenches. As soon as work is completed, the excavation should be backfilled as the protective system is dismantled. After the excavation has been cleared, workers should slowly remove the protective system from the bottom up, taking care to release members slowly.

In addition to cave–ins, there are other hazards from which workers must be protected during excavation–related work. These hazards include exposure to falls, falling loads, and mobile equipment. To protect employees from these hazards, OSHA requires the employer to take the following precautions:

• Keep materials or equipment that might fall or roll into an excavation at least 3 feet from the edge of excavations, or have retaining devices, or both.
• Provide warning systems such as mobile equipment, barricades, hand or mechanical signals, or stop logs, to alert operators of the edge of an excavation. If possible, keep the grade away from the excavation.
• Provide scaling to remove loose rock or soil or install protective barricades and other equivalent protection to protect employees against falling rock, soil, or materials.
• Prohibit employees from working on faces of sloped or benched excavations at levels above other employees unless employees at lower levels are adequately protected from the hazard of falling, rolling, or sliding material or equipment.
• Prohibit employees under loads that are handled by lifting or digging equipment. To avoid being struck by any spillage or falling materials, require employees to stand away from vehicles being loaded or unloaded. If cabs of vehicles provide adequate protection from falling loads during loading and unloading operations, the operators may remain in them.

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