Workplace Safety Guides

   Air and Water Concerns During Excavation


To prevent exposure to harmful levels of air contaminants and to assure acceptable atmospheric conditions, certain requirements must be met. Under certain conditions, atmospheres of excavations greater than four feet deep must be tested before employees may enter. Testing is required where oxygen deficiency that is less that 19.5 percent oxygen or a hazardous atmosphere exists or could reasonably be expected to exist. Examples of these conditions include excavations in landfill areas or where hazardous substances are stored nearby or where underground installations may have been ruptured.

Adequate precaution shall be taken to prevent employee exposure to atmospheres containing less than 19.5 percent oxygen and other hazardous atmospheres. These precautions include providing proper respiratory protection or ventilation. When controls, such as ventilation, are used to reduce the level of atmospheric contaminants to an acceptable level testing is to be conducted as often as necessary to ensure continuing safety. Emergency rescue equipment such as breathing apparatus, a safety harness and line, or a basket stretcher must be readily available where hazardous atmospheric conditions exist or can reasonably be expected to develop. This equipment must be attended when in use.

Employees entering deep and confined footing excavations are to wear a harness with a securely attached lifeline. The lifeline is to be separate from any line used to handle materials and is to be individually attended at all times while the employee wearing the lifeline is in the excavation.

Water is very likely to be present during the course of work in many excavations and is one of the major concerns during excavation operations. The actions of water against the sides of excavations can cause undermining and cave-ins. The presence of accumulated water in or around excavations must therefore be treated with caution. Employees shall not be permitted to work in excavations where water has accumulated or is accumulating unless adequate precautions have been taken to protect them. Necessary precautions vary with each situation but could include special support, shield systems, or water removal.

If water removal equipment is used, the equipment and its operation must be monitored by a competent person to assure continued proper operation. If excavation work interrupts the natural drainage of surface water, diversion ditches, dikes, or other means must be used to prevent surface water from entering the excavation and to provide safe drainage of the adjacent area.

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