Injury Illness Prevention Plan - Flipbook - Page 187
Health and Safety Program Manual
Teamwrkx
Construction, Inc.
Issue Date: 10/16/23
Revision Date: 10/16/23
Trenching and Excavation
Reference: A-15
During the visual test, the competent person should check for crack-line openings along the failure zone that
would indicate tension cracks, look for existing utilities that indicate that the soil has been previously disturbed,
and observe the open side of the excavation for indications of layered geologic structuring.
The competent person should also look for signs of bulging, boiling, or sloughing, as well as for signs of surface
water seeping from the sides of the excavation or from the water table.
In addition, the area adjacent to the excavation should be checked for signs of foundations or other intrusions
into the failure zone, and the evaluator should check for surcharging and the spoil distance from the edge of the
excavation.
Manual tests
Thumb penetration test- Attempt to press the thumb firmly into the soil in question. If the thumb penetrates
no further than the length of the nail, it is probably Type B soil. If the thumb penetrates the full length of the
thumb, it is Type C. It should be noted that the thumb penetration test is the least accurate testing method.
Dry strength test- Take a sample of dry soil. If it crumbles freely, or with moderate pressure into individual
grains, it is considered granular (Type C). Dry soil that falls into clumps that subsequently break into smaller
clumps (and the smaller clumps can only be broken with difficulty) it is probably clay in combination with gravel,
sand, or silt (Type B).
Plasticity or Wet Thread Test- Take a moist sample of the soil. Mold it into a ball and then attempt to roll it into
a thin thread approximately 1/8 inch in diameter by two inches in length. If the soil sample does not break when
held by one end, it may be considered Type B.
A pocket penetrometer, shear vane, or torvane may also be used to determine the unconfined compression
strength of soils.
Spoil
Temporary spoil shall be placed no closer than 2 feet from the surface edge of the excavation, measured from
the nearest base of the spoil to the cut. This distance should not be measured from the crown of the spoil
deposit. This distance requirement ensures that loose rock or soil from the temporary spoil will not fall on
workers in the trench.
Spoil should be placed so that it channels rainwater and other run-off water away from the excavation. Spoil
should be placed so that it cannot accidentally run, slide, or fall back into the excavation.
Permanent spoil should be placed some distance from the excavation.
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