ch depth.
It's important to note that this kind of sloping
can only be used for trenches less than 20 feet deep,
any deeper and the protection must be designed by a
registered professional engineer.
So now, let's look at the workers in the original
scene who were stuck in the trench as it started
to cave in.
But this time, the soil has been classified as
type B, the trench has been properly sloped, and the
spoil pile is moved away from the edges of the trench.
The trench walls are not caving in and the
workers are safe while they work.
Now let's review the shoring type of protective
system for trench workers.
Shoring uses various support systems to prevent
soil and the trench walls from moving.
There are different kinds of shoring systems, but
timber and aluminum hydraulic are the two basic types.
Aluminum hydraulic cylinders are the most common
type of shoring, and they are typically installed
using spot bracing, plywood, or stacked methods.
To install the shoring correctly, you must first
determine the soil type.
The type of soil and depth and width of the trench
determine the maximum vertical and horizontal spacing
used with the members of the shoring system.
If we use our example of a 3-foot wide, 10-foot
deep, 40-foot long trench in type B soil, the
shoring system being installed would need to
include 12 strong aluminum vertical shores, with
six on each side of the trench.
These shores, also called rails, will be connected
by hydraulic cylinders every 8 feet along the
length of the trench.
A hand pump pressurizes the hydraulic cylinders
until they fit tightly within the rails.
Now that the shoring's in place, let's look again
at the workers in the trench at the beginning of
As before, the workers are laying a sewer pipe into
the bottom of a trench.
But now the shoring system prevents the trench
walls from caving in and keeps the workers safe.
Sloping and shoring are ways to protect the sides
of the trench so they don't cave in.
Now, let's talk about shielding, which is a way to
protect the workers when they're inside the trench.
Shielding involves using trench boxes—also known as
trench shields—or other supports to protect workers
inside a trench from collapsing soil if a cave-in occurs.
The competent person should pick a trench box that is
right for the soil type and all other site conditions.
A trench box has two large plates, which are held
apart by four horizontal cross-members.
These plates, or "shields," must be between the
sides of the trench and the work area.
The shields are strong enough to protect workers
inside from a soil collapse.
The shields can be two feet above the bottom of the
trench as long as they can support the entire depth
of the trench and there is no caving under or
behind the shield.
The top of the shield should extend at least eighteen
inches above the level of any materials that could
cave into the trench.
Trench boxes are typically used in open areas, but
they can also be used with the sloping methods
So, let's see how a trench box could have saved the
workers that we saw at the beginning of the video.
For our example, we'll assume that the workers are
in a trench with type C soil and no sloping, but
working inside a trench box.
This time, as the workers lay the sewer pipe into
the bottom of the trench, they are protected
from any possible cave-ins.
This example shows the importance of employers
following OSHA's excavation standards to ensure
that workers are provided with a safe workplace.
These types of construction deaths are preventable.
The trench cave-in prevention measures shown here
save workers' lives.
Use these protections on the job:
it could be the difference between life and death.
If you would like more information,
contact OSHA at www.osha.gov