25.A.03 Protective systems.
Protective systems must have the capacity to resist without failure all loads that are intended or could reasonably be expected to be applied or transmitted to the system.
Trenching Safety
- The sides of all excavations in which employees are exposed to danger from moving ground must be guarded by a support system, sloping or benching of the ground, or other equivalent means.
- Excavations less than 5 ft (1.5 m) in depth and which a CP examines, determines and documents that there is no potential for cave-in do not require protective systems, however, a fixed means of egress must be provided.
- Sloping or benching of the ground must be in accordance with Section 25.C. d. Support systems must be in accordance with Section 25.D.
- Protective systems must have the capacity to resist without failure all loads that are intended or could reasonably be expected to be applied to the system.
- Shoring must be used for unstable soil or depths greater than 5 ft (>1.5 m) unless benching, sloping, or other acceptable plan is implemented by the Contractor and accepted by the GDA.
25.A.04 Stability of adjacent structures.
- Except in stable rock, excavations below the level of the base of footing of any foundation or retaining wall must not be permitted unless:
- (1) A support system, such as underpinning, is provided to ensure the stability of the structure and to protect employees involved in the excavation work or in the vicinity thereof; or
- (2) A RPE has approved the determination that the structure is sufficiently removed from the excavation so as to be unaffected by the excavation and that the excavation will not pose a hazard to employees.
- If the stability of adjoining buildings or walls is endangered by excavations, shoring, bracing, or underpinning designed by a qualified person must be provided to ensure the stability of the structure and to protect employees.
- Sidewalks, pavements, and related structures must not be undermined unless a support system is provided to protect employees and the sidewalk, pavement, or related structure.
25.A.05 Where it is necessary to undercut the side of an excavation, overhanging material must be safely supported.
25.A.06 Protection from water.
- Diversion ditches, dikes, or other means must be used to prevent surface water entering an excavation and to provide good drainage of the area adjacent to the excavation.
- Employees must not work in excavations in which there is accumulated water or in which water is accumulating unless the water hazards posed by accumulation is controlled.
- (1) Freezing, pumping, drainage, and similar control measures must be planned and directed by a RPE. Consideration must be given to the existing moisture balances in surrounding soils and the effects on foundations and structures if it is disturbed.
- (2) When continuous operation of ground water control equipment is necessary, an emergency power source must be provided. Water control equipment and operations must be monitored by the CP to ensure proper operation.
25.A.07 Protection from falling material.
- Employees must be protected (by scaling, ice removal, benching, barricading, rock bolting, wire mesh, or other means) from loose rock or soil that could create a hazard by falling from the excavation wall: special attention must be given to slopes that may be adversely affected by weather, moisture content, or vibration.
- Materials, such as boulders or stumps, that may slide or roll into the excavation must be removed or made safe.
- Excavated material must be placed at least 2 ft (0.6 m) from the edge of an excavation or must be retained by devices that are sufficient to prevent the materials from falling into the excavation. In any case, material must be placed at a distance to prevent excessive loading on the face of the excavation.
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25-3. What must be used for unstable soil or depths greater than 5 ft (>1.5 m) unless benching, sloping, or other acceptable plan is implemented by the Contractor and accepted by the GDA?
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