The document discusses excavation safety requirements for trenching and excavation work. It outlines major hazards like cave-ins, defines key terms, and describes the specific OSHA requirements for ensuring safe excavations. These include requiring protective systems to prevent cave-ins, means of access and egress, fall protection, protection from hazards like vehicles, falling loads, and water accumulation, and inspections by a competent person. It provides details on soil classification and the required sloping, shoring, or shielding based on soil type to protect workers from cave-ins.

1. Excavation Safety
Awareness Training
KING SALMAN
AIRBASE PROJECT,
DIRAB.

2. Objectives
We will discuss the
following:
• Excavations/Trenching:
– OSHA Specific excavation
requirements
– Requirements for protective
systems
1926 Subpart P

3. Definitions
• Excavation
– Man-made cut, cavity, trench, or depression
formed by earth removal.
• Trench
– Narrow excavation
– Depth is greater than the width, but not wider than
15 feet.
1926.650(b)

4. • Competent person
– Must have specific training in and be
knowledgeable about:
• Soils classification
• Use of protective systems
• Requirements of the
standard
– Must be capable of
identifying hazards,
and authorized to
eliminate them.
1926.650(b)
Definitions

5. Excavation Hazards
• Cave-ins are the greatest risk.
• Other hazards include:
– Asphyxiation due to lack of oxygen
– Inhalation of toxic materials/fumes
– Fire
– Machinery moving near edge of
excavation causing a collapse
– Severing underground utility lines
– Falls

6. Weight of Soil
• Weight of soil varies with type and moisture content.
• One cubic foot weighs 110 pounds to 140 pounds.
• One cubic yard (27 cubic
feet) of soil can weigh
more than 3,000 pounds.

7. Injury and Death
• Excavating is one of the
most hazardous
construction operations.
• Most accidents occur in
trenches 5-15 feet deep.
• Usually no warning before
a cave-in.

8. Specific Excavation Requirements
• (a) Surface encumbrances
• (b) Underground installations
• (c) Access and egress
• (d) Exposure to vehicular traffic
• (e) Exposure to falling loads
• (f) Warning system for mobile equipment
• (g) Hazardous atmospheres

9. Specific Excavation Requirements
• (h) Protection from hazards associated
with water accumulation
• (i) Stability of adjacent structures
• (j) Protection of employees from loose rock
or soil
• (k) Inspections
• (l) Fall protection

10. Surface Encumbrances
• All surface
encumbrances that create
a hazard to employees
must be removed or
supported to safeguard
employees.
1926.651(a)

11. • Estimated location of
utility installations
[sewer, telephone, fuel,
electric, water lines]
must be determined prior
to opening an
excavation.
1926.651(b)(1)
Underground Installations

12. 1926.651(c)(2)
Egress - Trench Excavation
• Stairway, ladder, ramp,
or other safe means of
egress must be located
in trench.
• Required if trench 4
feet or more in depth.
• Lateral travel distance
no more than 25 feet.

13. Ramp, ladder or stairs required at 4 feet or deeper.
25 feet 25 feet
1926.651(c)(2)
Egress - Trench Excavation

14. 1926.651(c)(1)(i)
Structural Ramps
• Structural ramps used for access or egress
of equipment must be designed by a
competent person.

15. • Is this correct?
1926.651(c)(2)
Egress - Trench Excavation

16. Exposure to Vehicle Traffic
• Employees exposed to vehicular traffic must
wear warning vests or other suitable garments
marked with or made or reflectorized or high-
visibility material.
1926.651(d)

17. What are the hazards?

18. 1926.651(e)
• Employees must not be permitted to work
under loads handled by lifting or digging
equipment.
Exposure to Falling Loads

19. What are the hazards?

20. What do these pictures have in common ?

21. 1926.651(f)
Warning System - Mobile Equipment
• Mobile equipment operated adjacent to
excavation and operator cannot see edge of
the excavation:
–Warning system
must be utilized.
• Barricades
• Hand or mechanical
signals
• Stop logs

22. Set up barriers or barricades around the edges of the excavation.
Place warning signs to warn people of the excavation. Divert
traffic away from the excavation area
Install flashing amber lights for night-time warning.
Prevention

23. Hazardous Atmospheres
• Testing conducted before employees enter
the trench and regularly thereafter.
1926.651(g)(1)

24. 1926.651(g)(1)
• Less than 19.5% or more than 23.5% oxygen
• A combustible gas concentration greater than 20% of the
Lower Flammable Limit (LFL)
• Test at 4 feet if suspected
– LEL
– Oxygen
– CO
– H2S
– Other toxic substances
Hazardous Atmospheres

25. 1926.651(g)(2)(i)
Emergency Rescue Equipment
• Emergency rescue
equipment must be
readily available where
hazardous atmospheric
conditions exist or
expected to develop
during work.
– Breathing apparatus
– Safety harness and line
– Basket stretcher

26. 1926.651(h)(3)
Water Accumulation
• Excavations subject
to runoff from heavy
rains require an
inspection by a
competent person.

27. 1926.651(h)(1)
Water Accumulation
• Employees must not work in
excavations where there is
accumulated water, or where
water is accumulating.
• Unless precautions taken to
protect workers:
– Water removal to control level of
water
– Special support or shield systems

28. • Water removal
equipment and
operations must be
monitored by a
competent person to
ensure proper
operation.
1926.651(h)(2)
Water Accumulation

29. Stability of Adjacent Structures
• Excavation below the
foundation that could
pose a hazard shall not
be permitted except:
• ‘
– Underpinning provided
– Stable rock
– Registered professional
engineer (RPE) has
approved
1926.651(i)(2)

30. Underpinning to
prevent structural
failure.
1926.651(i)(2)(i)
Underpinning

31. Stability of Adjacent Structures
• Sidewalks, pavements and appurtenant
structure must not be undermined unless
supported to protect
employees from
collapse of such
structures.
1926.651(i)(3)

32. • Adequate protection provided
to protect employees from loose
rock or soil that could pose a
hazard by falling or rolling
from an excavation face.
Protection of Employees from loose rock
or soil
1926.651(j)(1)

33. Belly bulge
Fissures
Extra load from
spoil pile
Potential Problems

34. • Employees must be protected from
equipment or materials that could fall or roll
into excavations.
– Materials and
equipment must be
kept 2 feet from edge
of excavation or use
retaining devices.
Protection of Employees
1926.651(j)(2)

35. Rule: 2 Feet
1926.651(j)(2)

36. 1. What’s the Hazard?

37. 1926.651(k)(1)
Inspections – Competent Person
• Daily and before the start of each shift.
• As dictated by the work
being done in the trench.
• After every rain storm and
other events that could
increase hazards, e.g.,
snowstorm, windstorm,
thaw, earthquake, etc.

38. Inspections
• Frequency of testing should be increased if
equipment is operating in trench as well as if
welding, cutting, or burning is done in trench.
1926.651(k)(1)

39. Is this okay?

40. 1926.651(l)(1)
• Walkways provided when crossing over
excavation.
• Standard guardrail
installed when more
than 6 feet above
a lower level.
Fall Protection

41. 1926.652(a)(1)
Protection of Employees
• Employees in an
excavation must be
protected from cave-ins
by adequate protective
system.
– Except when:
• Made entirely in stable
rock
• Excavation is less than 5
feet deep and examined
by competent person

42. Methods of Protection
• Sloping and benching
• Shoring (spaced sheeting, closed sheeting)
• Trench shield
• Other occasionally used systems
1926.652

43. Definitions
• Sloping
– Technique that employs a specific angle of
incline on the sides of the excavation.
• Shoring
– Structure that supports the sides of an excavation
and protects against cave-ins.
• Shield
– Structure able to withstand a cave-in and protect
employees.
1926.650(b)

44. 1926.652(a)(2)
Protective Systems
• Protective systems
shall have capacity to
resist without failure
all loads applied or
transmitted to the
system.

45. 1926.652(e)(1)(ii)
Installation and Removal
• Support systems must be installed and
removed in a manner that protects
employees from
cave-ins.

46. • Removal must begin
at, and progress from,
the bottom of the
excavation.
• Members released
slowly to note any
indication of possible
failure of remaining
members.
Installation and Removal
1926.652(e)(1)(V)

47. 1926.652(e)(2)(i) and (g)(2)
Installation and Removal
• Excavations of
material to a level not
greater than 2 feet
below the bottom of
the support system or
shield must not be
permitted.

48. What’s the hazard?

49. What’s the hazard?

50. What’s the hazard?

51. • Acceptable visual and
manual test for use in classifying
soils
• Sets forth requirements
Soil Classification
Appendix A

52. • Thread Test
• Ribbon Test
• Thumb Penetration Test
• Pocket Penetrometer
Tests use in classifying soils
Appendix A

53. Type A Soil
• Most stable: clay, silty clay, and hardpan
• Not fissured
• Not subjected to vibration
of any type
• Never been previously
disturbed
• No seeping water
Unconfined compressive strength
greater than 1.5 tons per square foot
(tsf)
Appendix A

54. Type B Soil
• Medium stability: silt, sandy
loam, medium clay and
unstable dry rock
• Previously disturbed soils
unless otherwise classified as
type C
• Soils that meet the
requirements of Type A
but are fissured or subject to
vibration Unconfined compressive strength
less than 1.5 tsf and greater than
0.5 tsf
Appendix A

55. Type C Soil
• Least stable: gravel, loamy sand, soft clay
• Submerged soil or dense,
heavy unstable rock
• Soil from which water is
freely seeping
Unconfined compressive strength 0.5
tsf or less
Appendix A

56. • Contains definitions
• Sets forth requirements
• Configurations of sloping and
benching
Sloping and Benching
Appendix B

57. Allowable Slopes
Soil Type Height/Depth
Ratio
Slope Angle
Stable rock Vertical 90°
Type A ¾ : 1 53°
Type B 1 : 1 45°
Type C 1 ½ : 1 34°
Type A (short term) ½ : 1 63°
(For a maximum excavation depth of 12 ft)
Table B-1

58. Excavations Made in Type “A” Soil
Simple Slope

59. Multiple Bench
Excavations Made in Type “A” Soil

60. Excavations Made in Type “A” Soil
Support or Shield System

61. Simple Slope
Excavations Made in Type “B” Soil

62. Excavations Made in Type “B” Soil
Multiple Bench

63. Support or Shield System
Excavations Made in Type “B” Soil

64. Excavations Made in Type “C” Soil
Simple Slope

65. Excavations Made in Type “C” Soil
Support or Shield System

66. Selection of Protective Systems
• Illustrates a graphic summary of
requirements contained in subpart P for
excavations 20 feet or less in depth.
• Protective systems for use in excavations
more than 20 feet in depth must be designed
by a registered professional engineer in
accordance with 1926.652(b) and (c).

67. Thank you