School Construction Insurance Pool, Inc.
Loss Control Notice
Excavation and Trenching
Excavating is recognized as one of the most hazardous construction operations. An
excavation is any man-made cut, cavity, trench, or depression in the earth’s surface
formed by earth removal. This can include anything from a sewer line installation to
multi-lane interstate highways. Dangers associated with excavation work include the
following: cave-ins; undetected underground utilities; water accumulation; hazardous
atmospheres; loose rock and soil; and creatures (such as snakes).
The Occupational Safety and Health Administration (OSHA) continues to cite companies
for: not having an adequate protective system; not making proper inspections; not
providing proper escape methods; and not placing excavated materials far enough away
from the dig. The specific OSHA regulations that pertain to excavation work can be
found in 29 CFR 1926.650 thru 652.
All digs require pre-planning. Before you start to excavate you should:

Contact underground utility companies and the property owner to ensure
all underground installations/utilities have been identified to prevent
damage to underground utilities (please refer to SCIP’s Loss Control
Notice regarding Underground Utility Protection).

Ensure underground installations/utilities are protected, supported or
removed as necessary to safeguard workers from electrocutions, fires, etc.

Remove or secure any surface obstacles, such as trees, rocks, and
sidewalks, that may create a hazard to personnel and equipment.

Classify the type of soil and rock deposits at the site. One visual and at
least one manual analysis must be made. This assists in identifying what
types of safety precautions must be used.

Excavations 20 feet or deeper must have a plan designed by a licensed
professional engineer.
The contractor must have a Competent Person to make daily inspections (or more
frequent inspections as necessary) of any excavation, the adjacent area, and the protective
system being used. A Competent Person is a person who has been trained in the current
OSHA excavation standard, is knowledgeable about soil analysis, protective systems, and
has the authority to shut down the job if hazardous or potential hazardous situations exist.
Before excavating work can begin, the soil type must be determined. The soil must be
classified as one of the following:
Stable Rock – Natural solid mineral material that can be excavated with vertical sides
and will remain intact while exposed.
Type A soil – Examples include clay, silty clay, sandy clay, clay loam and sometimes
silty clay loam and sandy clay loam.
Type B soil – Examples include silt, silt loam, sandy loam and sometimes silty clay loam
and sandy clay loam.
Type C soil – Examples include granular soils like gravel, sand, loamy sand, submerged
soil, and soil from which water is freely seeping, and submerged rock that is not stable.
Workers must be protected from cave-ins by a protective system designed according to
OSHA standards. Factors involved in designing a protective system include soil
classification, depth of cut, water content of soil, weather and climate changes, and other
operations in the vicinity. Types of protective systems include:

Proper sloping and/or benching of the sides of the excavation

Supporting the sides of the excavation with timber shoring or aluminum
hydraulic shoring

Placing a shield between the sides of the excavation and the work area
OSHA has created a chart to identify the Maximum Allowable Slopes for the different
types of soil (29 CFR 1926.652(4) Table B-1). This chart identifies that solid rock is the
most stable whereas Type C (sand, light gravel) is the most unstable, due to the increased
sloping requirement.
Soil or Rock Type
Solid Rock
Type A
Type B
Type C
Minimum Allowable Slopes for
Excavations Less than 20 feet deep
Vertical or 90°
¾:1 or 53°
1:1 or 45°
1 ½:1 or 34°
At a minimum, workers should know and practice the following while working in
excavations:

Always wear the proper required safety equipment

Know the emergency response procedures

In excavations where hazardous atmospheres exist or could exist, be sure
the Competent Person has tested the air and declared the atmosphere safe
to work in before entering the excavation.

Keep materials, spoils, and equipment that might fall or roll into an
excavation at least two feet from the edge.

Wear a warning vest or other suitable clothing, marked with or made of
reflectorized or high-visibility material when exposed to vehicle traffic.

Use warning barricades, hand or mechanical signals, or stop logs, to alert
equipment operators of the edge of an excavation.

Do not work in excavations where water has accumulated or is
accumulating unless adequate precautions have been taken

Do not cross over an excavation unless walkways are provided.
Guardrails must be provided if the walkway is six feet or more above the
bottom of the excavation.
If you need further assistance or would like help in pre-planning a job, please contact
Mike Coppa at (866) 252-7247 ext. 271 or via e-mail at mcoppa@the-trust.org. Thank
you.