Excavation Safety: Hazards, Prevention & Corrective Actions

1. Excavations Module 14

2. Objectives • After this module you should be able to • identify the most common excavation hazards • take the steps necessary to avoid those hazards

3. Safety Facts • As many as 400 workers die and another 4000 injured as a result of cave-ins each year • Most deaths occur in trenches 5-14 feet deep • Cave-ins cause death by: suffocation, crushing, loss of circulation, falling objects • 1 cubic foot of soil can weigh up to 140 lbs • 1 cubic yard of soil can weigh up to 3000 lbs

4. Excavation Hazards • Cave-in of a trench • Contacting underground utilities • Getting struck by falling objects • Falling into an excavation • Hazardous atmospheres • Equipment rolling into excavations

5. Competent Person • Every excavation job must have one • This person must be trained on and knowledgeable in • soils classification • the use of protective systems • the requirements of the OSHA standards • This person must be able to identify hazards and immediately eliminate them • Enter excavations only after their approval

6. competent persons must have the authority to take prompt corrective action

7. this 6’ deep vertical-sided trench is dangerous because it is not protected Corrective Actions: never enter a trench like this; notify your supervisor

8. What is a Cave-In? • The separation of a mass of soil or rock material from the side of an excavation and its sudden movement into the excavation either by falling or sliding that could entrap, bury, or otherwise injure and immobilize a worker

9. this worker is being exposed to a life threatening situation, an excavation with no cave-in protection Corrective Action: never enter a trench unless it is less than 5’ deep and you get permission from your supervisor or it has cave-in protection

10. Shielding

11. The Theory of Shielding • Shielding does not actually prevent a cave-in • Trench shields and boxes, if installed correctly, are designed to protect workers from the forces of a cave-in • In order for the shield to do its job, the worker must stay within the protection of the shield even when entering and exiting

12. this trench is not shielded to the trench bottom properly; these workers are still at risk for a cave-in Corrective Action: shield the trench to no more than 2’ from the bottom

13. the same shield is missing struts/crossbraces Corrective Action: always install manufactured shielding according to the manufacturer’s directions

14. this incomplete installation provides little if any protection; in fact, the panels themselves can become a crushing hazard Corrective Actions: always install manufactured cave-in protection according to the manufacture; never skip steps

15. these workers have left the protection of their trench box; a cave-in could happen at any moment Corrective Action: never work unprotected, cave-ins can happen anytime without warning

16. Shoring

17. The Theory of Shoring • Shoring prevents cave-ins • Trench shoring, if designed and installed correctly, counteracts the force of a cave-in • In order for the shoring to do its job, the worker must stay within the protection of the shoring even when entering and exiting

18. make-shift, improperly designed shoring does little other then provide a false sense of security Corrective Action: manufactured shoring should be used; install the shoring according to the manufacturer

20. manufactured aluminum shoring does little good either when improperly installed

21. Sloping

22. The Theory of Sloping • Sloping prevents cave-ins • Sloping, if done correctly, removes the risk of cave-ins by sloping the soil of the trench back from the trench bottom

23. this is a good example of a properly sloped excavation providing a safe workplace free from cave-in hazards

24. this is a good example of a properly sloped excavation providing a safe workplace free from cave-in hazards

25. this worker is able to work without the fear of a cave-in

26. Ramps, Ladders, and Stairs

27. the worker in this trench has no safe means of exit Corrective Action: for trenches 4’ deep or greater, install a ramp, ladder, or stairs no less than every 25’ from a worker in the trench

28. Additional Concerns • Underground utilities • Overhead hazards • Mobile equipment • Walkways • Water in excavations • Hazardous atmospheres

29. striking underground utilities can be deadly this worker has used the one-call system to locate utilities; also, he is using safe and acceptable means to find the exact location of the utility

30. this worker is at risk of being struck by falling rocks and excavated materials, in particular this soil spoil is too close Corrective Action: keep excavated material (spoil) at least 2’ from the edge of the excavation

31. overhead hazards can also be the tools and materials workers use Corrective Action: keep tools materials and other project related items at least 2 feet from the edge

32. when mobile equipment is operated adjacent to an excavation, the operator must have a clear and direct view of the edge of the excavation, or… … a warning system shall be utilized such as barricades, stop logs, or hand or mechanical signals; if possible, the grade should be away from the excavation

33. using this method to cross an excavation can result in a serious fall Corrective Action: construct a proper and safe walkway

34. this is an example of a proper walkway walkways or bridges must have a safety factor of 4, have a minimum clear width of 20”, be fitted with standard rails, and extend a minimum of 24” past the surface edge of the trench

35. the presence of water usually means soil that is unstable

36. excavations must be kept as water free as possible Corrective Actions: select, inspect, and use water removal equipment correctly; consider such things as air-quality and personal health issues

37. with the water pump running, a possible carbon monoxide exposure now exists excavations greater than 4 feet in depth must be evaluated for oxygen deficiency, flammability, and toxicity

38. these workers installed a high exhaust pipe to prevent asphyxiation

39. compressed gas cylinders are not to be brought into trenches

40. trying to keep as many air contaminants as possible above grade is a good idea

41. Case Study • A crew was installing conduit in an 8’ deep by 2’ wide trench. The equipment operator had gone into the company trailer to check blueprints when another worker informed him of a trench collapse.

42. Applicable Standards • 1926 Subpart P Excavations

43. Preplanning the work Protecting you from cave-ins Inspecting the excavation at least daily and throughout the shift as needed Taking prompt corrective action when needed Your Employer is Responsible For

44. Making sure a ladder is within 25’ of your work area when deeper than 4’ Ensuring that excavated dirt, rocks, and other materials are kept back 2’ from the excavation’s edge Testing the air in areas suspect to atmospheric hazards Responding to and correcting hazards pointed out by you, the worker Your Employer is Responsible For

45. Working defensively Following you company’s excavation and trenching safety rules Correcting the hazards you are able to correct Reporting to your supervisor the hazards you are unable to correct You are Responsible For

46. Always Remember • Never enter a vertical-sided trench unless it is less then 5’ deep and you get permission from your supervisor • Never enter a trench unless it is laid back, shielded, boxed, or in solid rock • If a trench box is used, never leave its protection while in the trench

47. Memory Check • How many feet must the excavated soil, your tools, and other supplies be kept back from the excavation’s edge? • 1 foot • 2 feet • 7.5 feet • 25 feet

48. Memory Check • At what depth must a ladder, ramp, steps or runway be present for quick worker exit? • 4 feet • 5 feet • 10 feet • it is never required

49. Memory Check • What is the greatest hazard facing a worker while working in a trench? • hazardous atmospheres • falls • cave-ins • falling objects

50. Memory Check • Unless a competent person indicates that there is a potential for a cave-in, at what depth is a protective system required for a trench? • 2 feet • 4 feet • 5 feet • 10 feet