Excavation:
Excavation shall include all ground breaking for foundations, sewers, underground process and utility
lines, trenching, pile driving, electrical conduits and cables, groundwater wells, soil borings, grout holes,
concrete floor cutting, guard posts, spill clean-up etc.
Trench:
Trench 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 m).
HAZARDS OF EXCAVATIONS:
Serious injury, fatality or property damage may occur during excavation jobs due to the following causes
and safety measures as described later shall be adopted to ensure safety of personnel and equipment.
Ground collapse is one of the
primary risks to be controlled in excavation work. Ground collapse can occur
quickly and without warning, giving a worker virtually no time to escape,
especially if the collapse is extensive. A buried worker is likely to die from
suffocation before help arrives (for example either the head is buried, or the
chest is so restricted by the weight of ground that the worker can no longer
breathe).
a. Collapse of earthwork due to lack of, inadequate, or weak shoring.
b. Persons, equipment / vehicles falling into excavations due to lack of barriers or inadequate fencing, warning signs & illumination
c. Soil from excavations not being thrown clear of the sides, causing overloading and collapsing of walls
d. Water seepage causing drowning or collapse of walls, failure to maintain shoring, particularly after rain storm
e. Persons working too close together causing hazards to each other
f. Asphyxiation and intoxication from exhaust gases of running engines which, contain CO and CO2 that may have accumulated at the bottom of the excavation
g. Asphyxiation by Carbon Dioxide that can be present in excavations caused by air stagnation through lack of ventilation, especially on low wind days. Symptoms are dizziness, pounding in the ears, and shortness of breath.
h. Exposure of personnel to toxic or flammable gases or liquid accumulation due to leaking pipelines/contaminated equipment/ buried hazardous materials/waste (e.g. Leaded sludge)
i. Exposure of foundations affecting or collapsing the supported structure.
j. The instability of any adjoining structure caused by the excavation; or Collapse of existing structures due to removal of the passive lateral forces acting as a counter or reaction force on its foundations
k. Sliding of soil due to removing top layers beside existing structures leading to tilting or failure of existing structures.
l. any previous disturbance of the ground including previous excavation
m. Workers not being provided with or not using proper tools for the job
n. Workers in the excavation being struck by soil or materials falling into the excavation.
o. Falls through unsafe means of access into or out of the excavation.
p. Workers being struck by excavating machinery, e.g., the bucket of the excavator.
q. Vehicles or equipment too close to the edge, causing the edge to collapse
r. Vehicles being driven into the excavation due to driving errors, inadequate warning signs, or the absence of stop blocks
s. Fire/explosion due to use of tools and tackles used during excavation.
E. g. Sparks generated by pneumatic/jack hammer when used without taking adequate precautions.
t. Vibrations due to machinery and heavy vehicles in close proximity
u. Hazards of high noise level due to use of mechanical equipment
v. Underground installations:
Striking of services, e.g., electricity/communication cables and oil/gas pipes, utility pipes
w. Hazards due to surface encumbrances such as sidewalks, trees, street appurtenances such as lighting pole, etc.
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