Page 20 - Trench and Excavation

and the depths to which it can be used in various soil types should be documented upon an
accompanying tabulated data sheet. This sheet should come from either the manufacturer or a
Registered Professional Engineer. This data must be on the job site during the use of the shield.
It is very important that the shield system be assembled and used in conformance with the
manufacturer's or Registered Professional Engineer's direction. The use of job-built shield
systems is permitted if it has been designed by an RPE or is in compliance with tabulated data
approved by an RPE.

Workers must exit the shield when it is being installed, removed, moved vertically, or when loads
are being moved above or within the shield. However, they may remain within the shield if it is
moved horizontally. Most trench shields are relatively short. They may be stacked to
accommodate deeper trenches if they have been designed to do so.

The shield must have the rated strength for the depth that it is being used at. Pre-existing linking
holes or mechanisms must be used to stack and secure shield systems together. NEVER DRILL
HOLES IN SHIELDING SYSTEMS TO FACILITATE BOLTING THEM TOGETHER.

If the soil is sloped in conjunction with the shield system, the shield system must extend at least
18 inches above the toe of the trench slope. If a vertical cut is made, the shield must extend only
to the top of the trench.
Workers may excavate the bottom of the trench to a depth which is not greater than 2 feet below
the bottom of the shield if the shield is rated for the entire depth and there is no sign of soil loss
from the sides or bottom. When shielding systems are damaged, they must be repaired and
inspected before being returned to service.
Adequate egress systems must be provided to allow for entry into
the shield system. Workers must not enter an unprotected area of
the trench in order to reach their means of egress. Secured ladders
must be spaced so that a worker does not have to go any farther than
25 feet laterally in order to reach a ladder. Remember that climbing
on the shield supports is not an acceptable means of egress and
means of egress must be provided at a depth of 4 feet and greater.

Sloping and Benching Systems

If enough surface room is available, sloping or benching the
trench walls will offer excellent protection without any
additional equipment. Cutting the slope of the excavation
back to its prescribed angle will allow the forces of cohesion
(if present) and internal friction to hold the soil together and
keep it from flowing down the face of the trench. The soil type
primarily determines the excavation angle.

Sloping - a method of protecting employees from cave-ins by excavating to form sides of an
excavation that are inclined away from the excavation to prevent cave-ins. OSHA provides slope
information based on the maximum allowable slope. To use the maximum allowable slope, site
conditions must be ideal. If any signs of distress are observed, the actual slope is required to be
less than the maximum allowable slope. Signs of distress that OSHA lists are:

Trench & Excavation
Competent Person Training P3 Safety Solutions LLC
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