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Module 4: Basic Tool Safety and Working Environment

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Attrezzi da giardino e sicurezza Scavo

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Trenching and Excavation Safety
Safety is crucial during any excavation job. Safety precautions must be exercised at all times to prevent injury to yourself or other workers.

Excavations are done for a number of reasons, including laying pipe and locating utility and sewage lines. During an excavation, earth is removed from the ground, creating a trench.

Trench
= a narrow excavation made below the surface of the ground in which the depth is greater than the width (the width does not exceed 15 feet).

Working in and around excavations is one of the most hazardous jobs you will ever do.

The design of excavation may not be your responsibility, but you should be aware of the safety hazards involved in the placement and design of excavation.

You must take safety precautions at all times to prevent injury to yourself and others.

Guidelines for Working in and around a Trench
Working in a trench exposes a worker to many potential hazards. Other than the possibility of injury from objects falling into the trench, the most obvious hazard is a trench failure.

Click on each type of situation related to the hazards of working in a trench to know more:

Cave-in
A trench wall could suddenly give way, sending you to the bottom of the trench.

Flooding
When you are working in a trench, flooding can be a concern. If a water or sewer main is ruptured while excavating, the trench can quickly fill with water.

Electrical Shock
Electrical shock is also a potential hazard in the trench. While excavating you could accidentally pierce the insulation of an electrical cable in the trench.

Indication of an Unstable Trench
A number of stresses and weaknesses can occur in an open trench or excavation. For example, increases or decreases in moisture content can affect the stability of a trench or excavation.

Tension cracks usually occur from one-quarter to half the distance from the top of a trench. Sliding or slipping may occur as a result of tension cracks.

Another indication of an unstable trench is boiling. Boiling is when water flows upward into the bottom of the cut. A high water table is one cause of boiling.

Trench Failure
The most common hazard during an excavation is trench failure or cave-in.

Using common sense and following all applicable safety precautions will make the trench a safer place to work.

To understand the seriousness or trench failure, consider what can happen when there is a shift in the earth that surrounds an unsupported trench. Workers could be buried when any of the following events happen:

• One or both edges of the trench cave in

• One or both walls slide in

• One or both walls tear away and collapse

Making the Trench Safer
There are several ways to make the trench a safer place to work.
Trench shoring, shielding, and sloping are used to protect workers and equipment.

Click on each term to know more and recognize the difference among them:

Shoring

Shoring supports the wall of a trench and prevents their movement and collapse.

Shields
Trench shields, also called trench boxes, are placed in unshored excavations to protect workers from wall collapse.

Sloping
Sloping an excavation means cutting its wall back at an angle to its floor.

Fall Protection
Many large excavations require the use of walkways so that workers can cross from one side of the excavation to the other.

Where these walkways are 4 feet or more above the ground or lower work level, the installation of guardrails is necessary.