žEXCAVATION
SAFETY
žYAWAR
HASSAN KHAN
ž
žCave-ins
are the greatest risk
ž•
Other hazards include:
ž
Asphyxiation due to lack of oxygen
ž
Inhalation of toxic materials
ž
Fire
ž
Moving machinery near the edge of
žthe
excavation can cause a collapse
ž
Accidental severing of underground
žutility
lines
ž
žExcavating
is one of the most
žhazardous
construction
žoperations
ž•
Most accidents occur in
žtrenches
5-15 feet deep
ž•
There is usually no warning
žbefore
a cave-in
ž
žExcavation
– a man-made cut, cavity, trench, or depression
žformed
by earth removal.
ž•
Trench – a narrow excavation. The depth is greater than the
žwidth,
but not wider than 15 feet.
ž•
Shield - a structure able to withstand a cave-in and protect
žemployees.
ž•
Shoring - a structure that supports the sides of an excavation
žand
protects against cave-ins.
ž•
Sloping - a technique that employs a specific angle of incline
žon
the sides of the excavation. The angle varies based on
žassessment
of impacting site factors.
ž
žThe
greatest risk at an excavation
ž• How
to protect employees from cave-ins
ž•
Factors that pose a hazard to employees working in
žexcavations
ž• The
role of a competent person at an excavation site
ž
žEmployees
should be protected from
žcave-ins
by using an adequately
ždesigned
protective system
ž•
Protective systems must be able to resist
žall
expected loads to the system
ž
žA
well-designed protective system
ž
Correct design of sloping and benching systems
ž
Correct design of support systems, shield systems, and other
žprotective
systems
žPlus
ž•
Appropriate handling of materials and equipment
žPlus
ž•
Attention to correct installation and removal
žEquals
ž•
Protection of employees at excavations
ž
žDesign
of Protective Systems
ž• The
employer shall select and construct :
ž
slopes and configurations of sloping and benching systems
ž
support systems, shield systems, and other protective
žsystems
ž•
Shield - can be permanent or portable; also known
žas
trench box or trench shield
ž•
Shoring - such as metal hydraulic, mechanical or
žtimber
shoring system that supports the sides
ž•
Sloping - form sides of an excavation that are
žinclined
away from the excavation
ž
žProtect
Employees Exposed
žto
Potential Cave-ins
ž•
Slope or bench the sides of
žthe
excavation,
ž•
Support the sides of the
žexcavation,
or
ž•
Place a shield between the
žside
of the excavation and
žthe
work area
ž
žFactors
Involved in Designing
ža
Protective System
ž•
Soil classification
ž•
Depth of cut
ž•
Water content of soil
ž•
Changes due to weather
žand
climate
ž•
Other operations in the
žvicinity
ž
žShoring
ž•
General
ž
Provides a framework to work in
ž
Uses wales, cross braces and uprights
ž
Supports excavation walls
ž•
OSHA tables provide shoring data
ž
Must know soil type
ž
Must know depth and width of excavation
ž
Must be familiar with the OSHA Tables
ž
žUsing
hydraulic jacks, the
žoperator
can easily drop
žthe
system into the hole
ž•
Once in place, hydraulic
žpressure
is increased to
žkeep
the forms in place
ž•
Trench pins are installed
žin
case of hydraulic failure
ž
žEquipment
used for
žprotective
systems must
žnot
have damage or
ždefects
that impair
žfunction.
ž• If
equipment is damaged,
žthe
competent person
žmust
examine it to see if it
žis
suitable for continued
žuse.
ž• If
not suitable, remove it
žfrom
service until a
žprofessional
engineer
žapproves
it for use.
ž
žProtection
from Vehicles
ž•
Install barricades
ž•
Hand/mechanical signals
ž•
Stop logs
ž•
Grade soil away from
žexcavation
ž•
Fence or barricade
žtrenches
left overnight
ž
žThe
weight and
žvibrations
of the
žcrane
make this a
žvery
hazardous
žcondition.
ž•
They should not be
žworking
under this
žcrane.
ž
žSpoils
ž•
Don’t place spoils within 2
žfeet
from edge of
žexcavation
ž•
Measure from nearest part
žof
the spoil to the
žexcavation
edge
ž•
Place spoils so rainwater
žruns
away from the
žexcavation
ž•
Place spoil well away from
žthe
excavation
ž
žOther
Excavation Hazards
ž•
Water accumulation
ž•
Oxygen deficiency
ž•
Toxic fumes
ž•
Access/Egress
ž•
Falls
ž•
Mobile equipment
ž
žWhen
water is present
žin an
excavation it is
žextremely
hazardous
žto
enter
ž
žTest
excavations more than 4
žfeet
before an employee
ženters
the excavation for:
ž
Oxygen deficiency
ž
High combustible gas
žconcentration
ž
High levels of other
žhazardous
substances
ž
žMeans
of Egress
žA
stairway, ladder,
žor
ramp must be
žpresent
in
žexcavations
that are
ž4 or
more feet deep,
žand
within 25 feet
žof
the employees.
ž
žProtection
from Falls, Falling Loads,
žand
Mobile Equipment
ž•
Install barricades
ž• Use
hand / mechanical signals
ž•
Grade soil away from excavation
ž•
Fence or barricade trenches left overnight
ž• Use
a flagger when signs, signals and barricades are
žnot
enough protection
ž
žMust
have had specific training
žin
and be knowledgeable
žabout:
ž
Soils classification
ž
The use of protective systems
ž
The requirements of the standard
ž•
Must be capable of identifying
žhazards,
and authorized to
žimmediately
eliminate hazards
ž
žA
competent person must
žmake
daily inspections of
žexcavations,
areas around
žthem
and protective
žsystems:
ž
Before work starts and as
žneeded,
ž
After rainstorms, high winds
žor
other occurrence which
žmay
increase hazards, and
ž
When you can reasonably
žanticipate
an employee will be
žexposed
to hazards
ž
žIf
the competent person
žfinds
evidence of a possible
žcave-in,
indications of failure
žof
protective systems,
žhazardous
atmospheres, or
žother
hazardous conditions:
žExposed
employees must be
žremoved
from the hazardous
žarea
žEmployees
may not return until
žthe
necessary precautions have
žbeen
taken
ž
žBefore
beginning excavation:
ž
Evaluate soil conditions
ž
Construct protective systems
ž
Test for low oxygen, hazardous
žfumes
and toxic gases
ž
Provide safe in and out access
ž
Contact utilities
ž
Determine the safety equipment
žneeded
ž
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