eLCOSH : Roadway Safety: Instructor Manual

Roadway Safety: Instructor Manual

Other languages: Versión en español

Share this using: |

Laborers' Health and Safety Fund of North America

This document is one in a program produced under an OSHA grant by a consortium of the Laborers' Health and Safety Fund N.A, the International Union of Operating Engineers, the American Road and Transportation Builders Assn, and the National Asphalt Pavement Assn. All of the documents from this set that are on eLCOSH can be found by clicking on Job Site, Heavy construction, and scrolling to the Street & highway heading. Or to download a complete version of the computerized program, go to http://wzsafety.tamu.edu.

Why Are Trenches Dangerous?

A trench is an excavation deeper than it is wide. Trenches more than 4' deep must be treated as confined spaces. An excavation with formwork 15 feet or less from a sidewall is also a trench.

Trenches can kill:

Workers can be buried alive.
Cave-ins can result from stresses in the walls, from nearby moving vehicles and equipment, or from spoil piles.
Water can collect in the bottom.
Flammable and toxic work products can build up in the trench.
Gas from nearby sewer or gas lines can migrate through the ground into the trench.

Before digging:

Call all electrical, gas, and communications utilities.
Use extreme caution with equipment near the trench rim.

Fig. T-1.

Fig. T-1. An excavation with formwork 15 feet or less from a sidewall is a trench.

Notes:

(See Case Studies No. 6 - 7)

Ask trainees: When does a trench become a confined space? Answer: OSHA Confined Space Standard 1915.4(p) defines "confined space" as a compartment of small size and limited access ... or other space which by its small size and confined nature can readily create or aggravate a hazardous exposure.

Ask trainees: How long does it take for a trench to collapse? (Answer: Seconds.) How much does the dirt weigh? (3,000 pounds per cubic yard.)

What if you are only buried up to your neck? Could you still breathe? (Answer: Usually not.)

CAUTION: If water collects in the bottom, it increases the potential for a cave-in.

How Do We Prevent Cave-Ins?

Trenches 5 feet or deeper require support — unless they are in solid rock.

The four basic types of trench support are:

Sloping — soil removed at an angle to increase stability.
Benching — a series of steps in the trench wall.
Shoring — a support system made of posts, wales, struts, and sheeting or aluminum hydraulic shoring.
Shielding — a protective frame or box. Shielding is intended to protect rescue workers after a cave-in.

Always keep spoil piles away from trench edge.

Fig. T-2A.

Fig. T-2A. Sloping.

Fig. T-2B.

Fig. T-2B. Benching.

Fig. T-2C.

Fig. T-2C. Shoring.

Fig. T-2D.

Fig. T-2D. Shielding.

Notes:

Remember: Soil weighs 3,000 pounds per cubic yard.

Ask trainees: Under what circumstances should you go into an unshored trench? (Answer: Never.)

What Else Does Excavation Require?

The employer should designate 'competent person' to monitor all trench work. The 'competent person' must inspect the trench:

At least daily and at the beginning of each shift.
After precipitation, a thaw, and other events that could increase hazards.
For disturbed ground, water, toxics, and other hazards.
For sagging or cracked walls or bottom bulges.
To assure that spoil is kept at least 2 feet from the trench edge.
For nearby vibration sources such as railroads or pile driving.
To assure that ladders are placed so that no worker is more than 25 feet from an exit.

The 'competent person' should stop the work if a hazard exists.

Fig. T-3A.

Fig. T-3A. The ‘competent person'must assure that spoil is kept at least 2 feet from the trench edge.

Fig. T-3B.

Fig. T-3B. The ‘competent person' must assure that ladders are placed so that no worker is more than 25 feet from an exit.

Notes:

‘Competent person' means "one who is capable of identifying existing and predictable hazards in the surroundings or working conditions ... and who has authorization to take prompt corrective measures to eliminate them."

Ask trainees: Who is the competent person on this job site?

Back to Contents

This paper appears in the eLCOSH website with the permission of the author and/or copyright holder and may not be reproduced without their consent. eLCOSH is an information clearinghouse. eLCOSH and its sponsors are not responsible for the accuracy of information provided on this web site, nor for its use or misuse.

©2002 Laborers Health & Safety Fund of North America,Washington, DC All rights reserved. This material was produced under grant number 46C1-HT21 from the Occupational Safety & Health Administration, U.S. Department of Labor to a consortium of the Laborers' Health & Safety Fund of North America (LHSFNA), the International Union of Operating Engineers (IUOE), the American Road & Transportation Builders Association (ARTBA), and the National Asphalt Pavement Association (NAPA). It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government. No statement made in this booklet should be construed to convey an impression that any member of the consortium, its affiliates, or employees have assumed any part of the employer's exclusive legal responsibility for providing a "safe and healthful workplace" as mandated by the Occupational Safety and Health Act. Produced for the consortium by FOF Communications.