Table of Contents

Explosion Hazards >>

Excavation, Trenches, and Earthwork

Hazards associated with excavation are cave-ins; the striking of underground utilities; falling tools, materials, and equipment; and hazardous air contaminants or oxygen-deficient environments.

A. The minimum safety requirements are as follows:

1. Before opening an excavation these actions should be taken:
   
   1. Notify all regional notification centers and all underground utility owners who are not members of the notification centers two working days before starting the work.
      
   2. Estimate the location of the underground utilities. 1541(b)(1), (2)
      
   3. Obtain a permit from DOSH if workers are required to enter an excavation that is 5 ft. or deeper. 341(a)(1)
      
2. While excavating, the exact locations of the underground utilities must be determined by safe and acceptable means. 1541(b)(3)
   
3. While the excavation is open, the underground utilities must be protected, supported, or removed as necessary. 1541(b)(4)
   

B. When employees are in an excavation, the following requirements apply:

1. Employees shall be protected from cave-ins by an appropriate protective system. 1541.1(a)(1)

   Exception: If excavations are made entirely in stable rock, or are less than 5 ft. deep, and a competent person has determined that there is no potential for a cave-in, no protective system is needed.

2. A competent person must be on site to do the following:
   
   1. Conduct inspections of the excavations, adjacent areas, and protective systems before the start of work; as needed throughout the shift; and daily for potential cave ins, failures, hazardous atmospheres,or other hazards. 1541(k)(1)
      
   2. Take prompt corrective action or remove employees from the hazard.
      
3. The competent person must be able to demonstrate the following:
   
   1. The ability to recognize all possible hazards associated with excavation work and to test for hazardous atmospheres.
      
   2. Knowledge of the current safety orders pertaining to excavation and trenching.
      
   3. The ability to analyze and classify soils.
      
   4. Knowledge of the design and use of protective systems.
      
   5. The authority and ability to take prompt corrective action when conditions change.
      

C. Requirements for protective systems include the following:

1. Protective system design must be based on soil classification: Stable rock, Type A, B, or C soils. 1541.1 Appendix A (b), (c)
   
2. Soil classification is required as follows unless the protective system design is based on Type C soil:
   
   1. Classification must take into account both site and environmental conditions. 1541.1 Appendix A (a)(1)
      
   2. Soil must be classified by a competent person as Type A, B, or C soil. 1541.1 Appendix A (c)(1)
      
   3. Classification must be based on the results of at least one visual and one
      
3. Standard shoring, sloping, and benching must be used as specified in 1540 and 1541.1(b) or according to tabulated data prepared by a registered engineer (see illustrations 6-8 below).
   
4. Protective systems for excavations deeper than 20 ft. shall be designed by a registered engineer. 1541.1 Appendix F
   
5. Additional bracing must be used when vibration or surcharge loads are a hazard. 1541.1 Appendix A
   
6. Excavations must be inspected as needed after every rainstorm, earthquake, or other hazard increasing occurrence (Water in the excavation may require a reclassification of soil type). 1541(k)(1)
   
7. Employees must be protected from falling materials by scaling, installation of protective barriers, or other methods. 1541(j)(1)
   
8. Uprights shall extend to the top of the trench and its lower end not more than 2 feet from the bottom of the trench. 1541(j)(1)
9. Employees must be protected from excavated or other material by keeping such material 2 ft. from the excavation edge or by using barrier devices. 1541(j)(2)
   
10. Ladders or other safe access must be provided within 25 ft. of a work area in trenches 4 ft. or deeper. 1541(c)(2)
    
11. Excavation beneath the level of adjacent foundations, retaining walls, or other structures is prohibited unless requirements of 1541(i) have been met. 1541(i)(1)
12. Shored, braced, or underpinned structures must be inspected daily when stability is in danger. 1541(i)(2)
    
13. Walkways or bridges with standard guardrails must be installed when employees or equipment are required or permitted to cross over excavations that are at least 6 ft. deep and wider than 30 in. 1541(l)(1)
    
14. Barriers must be erected around excavations in remote locations. All wells, pits, shafts, and caissons must be
    covered or barricaded, or if temporary, backfilled when work is completed. 1541(l)(2)
    

D. Safety orders pertaining to shafts and wells include the following:

1. All shafts and wells more than 5 ft. deep into which workers are required to enter must be retained with lagging, spiling, or casing. 1542(a)(1)
   
2. Tests or procedures shall be performed before entry into exploration shafts to ensure the absence of dangerous air contamination or oxygen deficiency. 1542(c)(3), 5158
   
3. An employee entering a bell-bottom pier hole or other deep or confined-footing excavation shall wear a harness that has a lifeline attended by another employee. 1541(g)(2)(B)
   
4. Shafts in other than hard, compact soil shall be completely lagged and braced. 1542(c)(1)
   
5. Head protection is required for workers who enter a well or shaft. 3381
   
6. Shafts more than 20 ft. deep are subject to the TSOs. 8403(a)