Dangers of Trenching and Excavation
Cave-ins pose the greatest risk and are much more likely than other excavation-related accidents
to result in worker fatalities.
Other potential hazards
include falls, falling
loads, hazardous atmospheres,
and
incidents involving mobile equipment. One cubic
yard of soil can weigh as much as a car. An unprotected trench is an early grave. Do not enter an unprotected trench.
Trenches 5 feet (1.5 meters)
deep or greater require
a protective system unless the excavation is made entirely in stable rock. If less than 5 feet deep, a competent person may determine that a protective system is not required.
Trenches 20 feet (6.1 meters) deep or greater require
that the protective system be designed by a registered
professional engineer
or be based on tabulated data prepared
and/or approved by a
registered professional engineer in accordance
with 1926.652(b) and (c).
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. A competent person is an individual who is capable
of identifying existing
and
predictable hazards or working conditions that are hazardous, unsanitary, or dangerous to workers,
soil types and protective
systems required, and who is authorized to take prompt corrective
measures
to eliminate these hazards and conditions.
General
Trenching and Excavation Rules
• Keep heavy equipment away from trench
edges.
• Identify other sources that might
affect trench stability.
• Keep excavated soil (spoils) and
other materials at least 2 feet (0.6 meters) from trench edges.
• Know where underground utilities are
located before digging.
• Test for atmospheric hazards such as
low oxygen, hazardous fumes and toxic gases when > 4 feet deep.
• Inspect trenches at the start of each
shift.
• Inspect trenches following a
rainstorm or other water intrusion.
• Do not work under suspended or raised
loads and materials.
• Inspect trenches after any occurrence
that could have changed conditions in the trench.
• Ensure that personnel wear high
visibility or other suitable clothing when exposed to vehicular traffic.