The document discusses excavation and trenching hazards. The greatest risk is cave-ins, which can be prevented by sloping, shielding, or shoring the sides of the excavation. A competent person must inspect excavation sites daily for hazards like cave-ins, hazardous atmospheres, or equipment issues. Other excavation dangers include water accumulation, toxic gas exposure, falls, and mobile equipment strikes. Proper protective systems, training, and planning are needed to safely perform excavation and trenching work.

1. Excavation & Trenching
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PPT-011-01
Bureau of Workers’ Compensation
PA Training for Health & Safety
(PATHS)
OSHA
1926
Subpart
P

2. Topics
 Excavation and Trenching Hazards
 Protection of Employees
 Protective Systems Design
 Cave-in Hazards
 Competent Person
 Inspection of Excavations
 Site Evaluation Planning
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3. Focus on Training
• The greatest risk at an excavation
• How to protect employees from cave-ins
• Factors that pose a hazard to employees
working in excavations
• The role of a competent person at an
excavation site
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4. 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 (also called box).
 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.
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5. Competent Person
Must have had specific
training in and be
knowledgeable about:
→ Soils classification
→ The use of protective
systems
→ The requirements of
the standard
Must be capable of
identifying hazards and
authorized to immediately
eliminate them.
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6. Excavation Hazards
Cave-ins are the greatest risk
Other hazards include:
 Asphyxiation due to a lack
of oxygen
 Inhalation of toxic
materials
 Moving machinery near the
edge of the excavation can
cause a collapse
 Accidental severing of
underground utility lines
 Fire
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7. Injury and Death
 Excavating is one of the
most hazardous
construction operations.
 Most accidents occur in
trenches 5-15 feet deep.
 There is usually no
warning before a cave-in.
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8. Protection of Employees
Employees should be protected from cave-ins
by using an adequately designed protective
system
Protective systems must be able to resist all
expected loads to the system
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9. Protective Systems Requirements
A well-designed protective system
Correct design of:
- sloping and benching systems
- support systems
- shield systems
- other protective systems
+
Appropriate handling of materials and equipment
+
Attention to correct installation and removal
=
Protection of employees at excavations
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10. Design of Protective Systems
The employer shall select and construct :
→ Slopes and configurations of sloping and
benching systems
→ Support systems, shield systems, and other
protective systems
 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
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11. Employee Protection
Protect Employees
Exposed to Potential Cave-
ins.
 Slope or bench the sides
of the excavation,
 Support the sides of the
excavation, or
 Place a shield between
the side of the
excavation and the work
area.
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12. Cave-in Hazard
This excavation has
inadequate support
posts and egress
access.
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Inadequate protective system

13. Inadequate Protective System
This worker is in a
trench with no
protective system that
is neither sloped nor
benched and has no
means of egress.
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14. Protective System Design
Factors Involved:
 Soil classification
 Depth of cut
 Water content of soil
 Changes due to
weather and climate
 Other operations in the
vicinity
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15. Shoring
General
▪ Provides a framework to work in
▪ Uses wales, cross braces and uprights
▪ Supports excavation walls
OSHA tables provide shoring data
▪ Must know soil type
▪ Must know depth and width of excavation
▪ Must be familiar with the OSHA Tables
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16. Trench Shield
A trench shield (also
called a trench box)
was built around this
work area.
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17. Hydraulic Trench Support
 Using hydraulic jacks
the operator can
easily drop the
system into the hole
 Once in place,
hydraulic pressure is
increased to keep the
forms in place
 Trench pins are
installed in case of
hydraulic failure
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18. Materials and Equipment
 Equipment used for
protective systems must
not have damage or
defects that impair
function.
 If equipment is damaged,
the competent person
must examine it to see if
it is suitable for
continued use.
 If not suitable, remove it
from service until a
professional engineer
approves it for use.
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Trench Box

19. Protection from Vehicles
 Install barricades
 Hand/mechanical signals
 Stop logs
 Grade soil away from
excavation
 Fence or barricade trenches
left overnight
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20. Hazardous Conditions
 The weight and
vibrations of the crane
make this a very
hazardous condition.
 They should not be
working under this
crane.
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21. Spoil Piles
 Don’t place spoils within
2 feet from edge of
excavation
 Measure from nearest
part of the spoil to the
excavation edge
 Place spoils so rainwater
runs away from the
excavation
 Place spoil well away
from the excavation
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22. Other Excavation Hazards
 Water accumulation
 Oxygen deficiency
 Mobile Equipment
 Access/Egress
 Toxic Fumes
 Falls
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23. Water is Hazardous
When water is
present in an
excavation it is
extremely
hazardous to enter.
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Note: Workers not wearing hardhats
to protect them from materials falling
into the trench!

24. Water = Cave-in Hazard
These workers must be protected from cave-in. Note the
water in the bottom of the trench. Very hazardous condition!
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25. Hazardous Atmospheres
Test excavations more
than 4 feet before an
employee enters the
excavation for:
▫ Oxygen deficiency
▫ High combustible
gas concentration
▫ High levels of
other hazardous
substances
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26. Means of Egress
A stairway, ladder, or
ramp must be present
in excavations that
are 4 or more feet
deep, and within 25
feet of employees
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This ladder does not meet the
requirements of the standard
The ladder should extend 3 feet
above the excavation

27. Access and Egress
These two ladders
which are lashed
together are not
an adequate
means of egress.
The ladder should
extend 3 feet
above the top of
the excavation.
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28. Special Protection
From Falls, Falling Loads and Mobile Equipment:
 Install barricades
 Use hand/mechanical signals
 Grade soil away from excavation
 Fence or barricade trenches left overnight
 Use a flagger when signs, signals and
barricades are not enough protection
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29. Inspection of Excavations
A competent person must
make daily inspections of
excavations, areas around
them and protective systems:
 Before work starts and as
needed,
 After rainstorms, high winds
or other occurrence which
may increase hazards, and
 When you can reasonably
anticipate an employee will
be exposed to hazards.
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30. Inspections of Excavations
If competent person finds
evidence of a possible cave-in,
indications of failure of
protective systems, hazardous
atmospheres, or other
hazardous conditions:
 Exposed employees must be
removed from hazardous
area
 Employees may not return
until the necessary
precautions have been
taken.
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31. Site Evaluation Planning
Before beginning excavation:
 Evaluate soil conditions
 Construct protective
systems
 Test for low oxygen,
hazardous fumes and
toxic gases
 Provide safe in and out
access
 Contact utilities
 Determine the safety
equipment needed
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Fissure

32. Summary
• The greatest risk in an excavation
is a cave-in.
• Employees can be protected
through sloping, shielding, and
shoring the excavation.
• A competent person is responsible
to inspect the excavation.
• Other excavation hazards include
water accumulation, oxygen
deficiency, toxic fumes, falls,
and mobile equipment.
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33. Contact Information
Health & Safety Training Specialists
1171 South Cameron Street, Room 324
Harrisburg, PA 17104-2501
(717) 772-1635
RA-LI-BWC-PATHS@pa.gov
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34. Questions
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