Hazards of Excavation

The words on each slide as the author wrote them, read from the file by software so they can be searched. Layout, pictures and tables are not shown here: the slides above and the download are the original.

1. Slide 1

   Hazards of Excavations

   • This material was produced under a grant (SH-31234-SH7) from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does the mention of trade names, commercial products, or organization imply endorsement by the U.S. Government.
2. Slide 2

   Objectives

   • Identify what a trench is
   • Review fatality reports
   • Define definitions of different components of trenches
   • Identify hazards of the excavations
   • Identify protective measures
3. Slide 3

   What is a Trench?

   • Trench (Trench excavation) means a narrow excavation
   • (in relation to its length) made below the surface of the ground. In general, the depth is greater than the width, but the width of a trench (measured at the bottom) is not greater than 15 feet (4.6 meters).
   • An excavation is any man-made cut, cavity, trench, or depression in an earth surface formed by earth removal.
4. Slide 4

   Fatality reports

   • U.S. Bureau of Labor Statistics (BLS) data show that 271 workers died in trenching or excavation cave-ins from 2000 through 2006.
5. Slide 5

   The greatest risk

   • Cave-ins are the leading cause of deaths with excavations
   • Little to no warning before sidewall gives away
   • One of the most hazardous construction operations
   • Cubic yard of soil weights up to 3000 lbs.
6. Slide 6

   Osha Trench Compliance

   • https://www.youtube.com/watch?v=0wmcD3aM8X4
   • OSHA inspector enters a jobsite with individuals inside an excavation with inadaquate protection from the excavation hazards.
7. Slide 7

   Video Break down

   • What were the hazards of the excavation?
   • Was there any protection?
   • What could have been done differently?
8. Slide 8

   Introduction to Excavations

   • Source: https://www.youtube.com/watch?v=EIthR6akGtw
   • Video: This video shows definitions relating to excavations
9. Slide 9

   Definitions

   • Excavation – a man-made cut, cavity, trench, or depression formed by earth removal.
   • Trench – a narrow excavation. The depth is greater than the width, but not wider than 15 feet.
   • Shield - a structure able to withstand a cave-in and protect employees
   • Shoring - a structure that supports the sides of an excavation and protects against cave-ins
   • Sloping - a technique that employs a specific angle of incline on the sides of the excavation. The angle varies based on assessment of impacting site factors.
10. Slide 10

    When do you need protection?

    • All trenches 5 feet or deeper require a protective system unless the excavation is made entirely of stable rock.
    • Unprotected Trench
11. Slide 11

    General hazards

    • The greatest risk from excavations is cave-ins
    • Other risks while working inside or near an Excavation include:
    • Water
    • Inhalation hazards
    • Lack of oxygen
    • Underground utilities
    • Equipment
    • Spoils close to the edge
    • Falls
    • Egress
12. Slide 12

    Role of Competent person

    • OSHA standards require that employers inspect trenches daily and as conditions change by a competent person before worker entry to ensure elimination of excavation hazards
    • Competent Person- is one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them
13. Slide 13

    Excavations in Construction/Trenching

    • Source: https://www.youtube.com/watch?
    • v=cFYkeT0Yk6k
    • Video: This video shows the importance of using a system to protect workers from excavation hazards, and having a competent person on site to ensure all hazards are eliminated.
14. Slide 14

    Video Break down

    • What were the hazards of the excavation?
    • Was there any protection?
    • What could have been done differently?
15. Slide 15

    Cave-in protection

    • Four main types
    • Shield - can be permanent or portable. Also known as trench box or trench shield.
    • Shoring - such as metal hydraulic, mechanical or timber shoring system that supports the sides
    • Sloping - form sides of an excavation that are inclined away from the excavation
    • Benching - excavating the sides of an excavation to form one or a series of horizontal levels or steps
16. Slide 16

    Sloping

    • Inclining the trenching material away from the excavation, so in case of an cave in the material won’t fall from the sides crushing workers inside the excavation. Factors to take into account:
    • Soil type
    • Materials adjacent to excavation
    • Work done around excavations
    • Water
    • Weather
17. Slide 17

    Shields

    • Shields are engineered structures that take into account the trenches many hazards, and minimizes the hazards of material falling into the excavation and injuring the occupants inside. Some of the factors to consider with shields are:
    • Depth of cut
    • Weather
    • Water
    • Material to be used in trench
    • Other operations in the vicinity
    • Spoil piles
18. Slide 18

    Shoring

    • Installing engineered supports directly to the walls of the excavation, it is designed to prevent soil movement. Factors to consider when using this protective system:
    • Soil type
    • Strengths of support system
    • Water
    • Weather
    • Work done around excavation
19. Slide 19

    Benching

    • Benching is the act of cutting shelves into the sidewalls of the excavation to ensure if there is a cave-in the trench material will not cause harm to the worker. Things to take into consideration with this protective system:
    • Soil type
    • Weather
    • Water
    • Other operations onsite
20. Slide 20

    Other Hazards inside an Excavation include:

    • Water
    • Inhalation hazards
    • Lack of oxygen
    • Underground utilities
    • Equipment
    • Spoils close to the edge
    • Falls
    • Egress
    • Ergonomic
    • Temperature extremes
21. Slide 21

    Water

    • Causes the sides to become unstable
    • Cave-ins
    • Drowning hazard
    • Electrocution hazard if electrical equipment present
    • Inspect trenches following a rainstorm or other water intrusion
22. Slide 22

    Inhalation hazards

    • Carbon Monoxide
    • Bonds with the cells hemoglobin
    • 50 times tighter
    • 200 times stronger
    • Compared to oxygen's bond to hemoglobin
    • Work done in the excavation
    • Painting
    • Welding
23. Slide 23

    Lack of Oxygen

    • Room Oxygen -21%
    • Oxygen Deficient ≤
    • 19.5%
    • Oxygen Enriched ≥
    • 23.5%
    • Oxygen can be displaced
    • Different gasses and
    • compounds in the trench and surrounding area
    • The work performed in
    • the trench
    • Oxygen can be absorbed
    • Rust is the oxidization of metal
    • Chemical processes in the trench
24. Slide 24

    Underground utilities

    • Water
    • We already discussed
    • Electrical
    • Electrocution hazard- 75 mA can cause cardiac arrest
    • Natural Gas
    • Explosion hazards- high pressures are used to transport natural gas through underground lines
    • Always locate lines before you begin excavations, ensure all lines uncovered are supported properly
25. Slide 25

    Equipment

    • Can cause inhalation hazards
    • Carbon Monoxide
    • Tip into trench
    • If the trench is unseen use barriers to prevent equipment from getting to close
    • Cause a cave-in
    • Moving earth equipment
    • Vibrations from equipment
26. Slide 26

    Spoil Pile (excavated soil)

    • Spoil piles need to be located at least 2 feet away from the edge of the excavation, and it may need to be further away depending on conditions.
    • Causes extra weight on the trench walls
    • Even properly supported trench can be dangerous if spoil can fall into excavation
27. Slide 27

    Falls

    • To ensure the excavation is safe from falls
    • Place a barrier around the excavation to ensure everyone knows where it is
    • Place bright colored or reflective tape around to see in low light conditions
    • Ensure signs are properly posted to ensure the excavation location is apparent
    • Fall protection required at 6’
28. Slide 28

    Egress

    • OSHA standards require safe access and egress to all excavations, including ladders, steps, ramps, or other safe means of exit for employees working in trench excavations 4 feet or deeper
    • Located within 25’ of all workers
29. Slide 29

    Ergonomic

    • Study of how environmental factors effect the body
    • Body mechanics
    • Using equipment
    • Right tool for the job
    • Job rotation
    • Repetitive motion injuries
30. Slide 30

    Temperature extremes

    • Cold Stress
    • Heat Stress
    • Cold stress occurs by
    • from heat rash and heat
    • driving down the skin temperature and eventually the internal body temperature (core temperature).
    • This may lead to serious
    • health problems, and may cause tissue damage, and possibly
    • cramps to heat exhaustion and heat stroke. Heat stroke can result in death.
    • requires immediate
    • medical attention.
31. Slide 31
    • Hazard Identification
32. Slide 32

    Hazard identification

    • Shoring not adequate
    • No real protective system
    • Limited access zone
    • Vehicles in close
    • proximity
33. Slide 33

    Hazard Identification

    • Improper benching
    • No egress
    • Unprotected edge
34. Slide 34

    Hazard Identification

    • These workers are not
    • protected from a cave-in, nor do they have any apparent safe access or egress from the trench
35. Slide 35
    • Worker Rights and responsibilities
36. Slide 36

    Employee Rights & Responsibilities Occupational Safety and Health Act of 1970

    • To assure safe and healthful working conditions for working men and women
    • By authorizing enforcement of the standards developed under the Act
    • By assisting and encouraging the States in their efforts to assure safe and healthful working conditions
    • By providing for research, information, education, and training in the field of occupational safety and health…
37. Slide 37

    Employee Rights & Responsibilities

    • You have the right to:
    • A safe and healthful workplace
    • Know about hazardous chemicals
    • Information about injuries and illnesses in your workplace
    • Complain or request hazard correction from employer
38. Slide 38

    Employee Rights & Responsibilities You have the right to:

    • File a confidential complaint with OSHA to have their workplace inspected.
    • Receive information and training about hazards, methods to prevent harm, and the OSHA standards that apply to their workplace. The training must be done in a language and vocabulary workers can understand.
    • Get copies of their workplace medical records and exposure records.
    • Participate in an OSHA inspection and speak in private with the inspector.
39. Slide 39

    Employee Rights &

    • Responsibilities Continued:
    • File a complaint with OSHA if they have been retaliated or discriminated against by their employer as the result of requesting an inspection or using any of their other rights under the OSH Act.
    • File a complaint if punished or discriminated against for acting as a “whistleblower” under the additional 21 federal statutes for which OSHA has jurisdiction.
40. Slide 40

    Whistleblower Protection

    • http://www.whistleblowers.gov/