Trenching and Excavation Safety
Excavating is recognized as one of the most hazardous construction operations, killing an average of 33 people and injuring hundreds each year. The Occupational Safety & Health Administration (OSHA) recently updated its standard to simplify many of the existing provisions and to add and clarify definitions, eliminate duplicate provisions and ambiguous language and give employers added flexibility in providing protection for employees. The following information summarizes these changes.
Trenching and Excavation Requirements
Develop safety checklists before preparing a bid to make certain there is adequate information about the job site and all equipment needed is on hand. Checklists should incorporate elements of relevant OSHA standards as well as other information necessary for safe operations. Specific site conditions to be considered include:
- Nearness of structures and their conditions
- Surface and groundwater
- Water table
- Overhead and underground utilities
Competent Person Evaluations for Trenching and Excavating Safety
Authority to correct hazardous trenching or excavating situations should be clearly communicated and enforced. OSHA requires that a competent person inspect excavations and adjacent areas for possible cave-ins, failures of protective systems, equipment and hazardous atmospheres or conditions daily. If these conditions are encountered, exposed employees must be removed from the hazardous area until the necessary safety precautions have been taken.
Excavation Protective Systems
Designing a protective system can be complex due of the number of factors involved, such as soil classification, depth of cut, water content of soil, changes due to weather and climate or other operations in the vicinity.
OSHA requires that employees exposed to potential cave-ins be protected by sloping or benching the sides of the excavation. This is done by supporting the sides of the excavation or by placing a shield between the side of the excavation and the work area.
The OSHA standard provides several methods and approaches for designing protective systems, which provide the required level of protection against cave-ins. At least one copy of the information, including the identity of the registered professional engineer who approved the data, must be kept at the worksite during construction of the protective system.
Installing and Removing Excavation Protective Systems
Per OSHA standards, the following procedures are required for the protection of employees when installing protective systems:
- Securely connect members of protective systems
- Safely install protective systems
- Never overload members of protective systems
- Install other structural members to carry loads imposed on the support system when temporary removal of individual members is necessary
As soon as work is completed, backfill the excavation as the protective system is dismantled. After the excavation has been cleared, workers can slowly remove the protective system from the bottom up, taking care to release members slowly.
Trenching and Excavation Hazards
Trenching and excavation present serious risks to all workers involved, with the greatest risk being a cave-in. When these accidents occur, they are much more likely to result in worker fatalities than other excavation-related accidents.
Strict compliance with all sections of the OSHA standard will help reduce the risk of cave-ins, as well as other excavation-related accidents. Be aware of the following common hazards:
Falls and Equipment—To protect employees from falls, falling loads and mobile equipment, OSHA requires that the employer take the following precautions:
- Keep materials or equipment that might fall or roll into an excavation at least two feet from the edge, 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
- Prohibit employees from working on faces of sloped or benched excavations at levels above other employees
- Prohibit employees from working under loads that are handled by lifting or digging equipment
Water Accumulation—OSHA prohibits employees from working in excavations where water has accumulated or is accumulating unless adequate protection has been provided. If water removal equipment is used to control or prevent water from accumulating, the equipment and operations of the equipment must be monitored by a competent person to ensure proper use.
Hazardous Atmospheres—Before any employee enters an excavation greater than 4 feet in depth or where oxygen deficiency or a hazardous atmosphere exists or could reasonably be expected to exist, a competent person must perform atmospheric testing to determine if a hazardous condition exists. If hazardous conditions exist, controls such as proper respiratory protection or ventilation must be provided.
Access and Egress—Under the OSHA standard, the employer must provide safe access and egress to all excavations. When employees are required to be in trench excavations 4 feet deep or more, adequate means of exit, such as ladders, steps, ramps or other safe means of egress must be provided within 25 feet of lateral travel.
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